chem soc rev · this ornal is c the royal society of chemistry 2013 chem. soc. rev., 2013...

6990 Chem. Soc. Rev., 2013, 42, 6990--7027 This journal is c The Royal Society of Chemistry 2013

Cite this: Chem. Soc. Rev.,2013,42, 6990

Synthesis of binaphthyl based phosphine andphosphite ligands

Mariette M. Pereira,*a Mario J. F. Calvete,a Rui M. B. Carrilhoa and Artur R. Abreuab

The development of large scale synthesis of enantiopure and thermally stable (R)- and (S)-BINOL

molecules constitutes a key milestone in the field of asymmetric catalysis. Particularly, a great variety of

chiral binaphthyl-based phosphorus compounds, herein represented by phosphite and phosphine

classes, have earned considerable relevance due to their versatility as ligands in enantioselective metal-

catalysed reactions, allowing the preparation of optically active products with the desired enantiopurity.

This review highlights the most relevant concepts and accounts regarding general synthetic procedures

for binaphthyl-based mono- and bidentate phosphites and phosphines. Furthermore, the search for

environmentally benign chemical catalytic processes compelled us to also give special attention to the

functionalisation of binaphthyl-based phosphorus ligands for use in alternative reaction media. When

available, a critical selection of their applications in catalysis is briefly assessed.

1. Introduction

The careful selection of a suitable chiral backbone has becomea crucial procedure to embark on the synthesis of any modernligand for asymmetric catalysis. Several natural building blockshave been widely used for the development of chiral ligand

a Departamento de Quımica, Universidade de Coimbra, Rua Larga, 3004-535,

Coimbra, Portugal. E-mail: [email protected]; Tel: +351 239854474b Luzitin SA, Edificio Bluepharma, S. Martinho Bispo, Coimbra, Portugal

Mariette M. Pereira

Mariette M. Pereira obtained herPhD in Organic Chemistry in1992 at the University ofCoimbra and worked as FellowAssistant Researcher at theUniversity of Liverpool in 1993and University Autonoma deBarcelona from 1997–1998. Shehas been Associate Professor withHabilitation at the University ofCoimbra since 2007 and Directorof Chemistry Research Labora-tory of Luzitin Lda, a pharmaceu-tical spin-off. Her current

research interests are the synthesis of chiral binaphthyl basedligands for the development of asymmetric catalysts for carbonyla-tion tandem reactions and development of sensitizers based ontetrapyrrolic macrocycles for biomedicinal applications and envir-onmental catalysis. She has published ca. 100 peer-reviewedpapers in international journals, 2 books, and 4 book chaptersand is the inventor of 2 patents.

Mario J. F. Calvete

Mario J. F. Calvete received hisIndustrial Chemistry diplomafrom University of Coimbra in2000 and his PhD in NaturalSciences–Organic Chemistry in2004, from Eberhard Karls Uni-versity of Tubingen, Germany,with Prof. Dr h. c. MichaelHanack. After a two-year stay atTubingen as a postdoctoral fellowin Industry/University, hereturned to Portugal for a post-doctoral stay at University ofAveiro. In 2010 he was appointed

as Auxiliary Researcher at University of Coimbra. He is also InvitedAuxiliary Professor and his current research interests are tetra-pyrrolic macrocycle design and other heterocyclic ligands and theiruses in homogeneous/heterogeneous catalysis and theranostics. Hehas published ca. 40 peer-reviewed papers in international journalsand 2 book chapters.

Received 26th March 2013

DOI: 10.1039/c3cs60116a

www.rsc.org/csr

Chem Soc Rev

REVIEW ARTICLE

Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02

.

View Article OnlineView Journal | View Issue

http://dx.doi.org/10.1039/c3cs60116a

http://pubs.rsc.org/en/journals/journal/CS

http://pubs.rsc.org/en/journals/journal/CS?issueid=CS042016

This journal is c The Royal Society of Chemistry 2013 Chem. Soc. Rev., 2013, 42, 6990--7027 6991

libraries, although inherent restrictions were often imposed bythe natural existence of a single enantiomer. However, theemergent synthetic availability of 1,10-bi-2-naphthol (BINOL)1

in both (R) and (S) enantiomerically pure forms has guided thescientific community towards a huge development in synthesisof new materials and chiral ligands.2 Nowadays, BINOL and thepartially hydrogenated H8-BINOL3–6 (Fig. 1) are consideredparadigmatic ligands, systematically used in a diversity ofasymmetric catalytic reactions, namely carbon–carbon bondformation reactions, including Mannich, Strecker, Diels–Alder,Aldol, Friedel–Crafts, Michael addition and olefin methathesisas well as in heteroatom-transfer reactions, such as epoxidationand Baeyer–Villiger, among others.7

Moreover, chiral phosphorus ligands based on the binaphthylbackbone have earned a prominent status, shown by their multi-talented application in a large number of asymmetric catalyticreactions.8 Thus, the applied synthetic methodologies for prepara-tion of binaphthyl-based phosphorus ligands are a topic with

upmost significance. The insertion of carbon, oxygen or nitrogenatoms in the phosphorus first coordination sphere may lead tothe preparation of diverse families of phosphorus ligands withdifferent chemical properties.9,10 There are several reviews onsynthetic procedures for binaphthyl-based phosphorus ligands,like phosphoramidites, phosphonites, phophinites, aminophos-phinites, diamidophosphites and phosphonates.11,12 For the-matic coherence, this review is mainly focused on the mostrelevant synthetic aspects of mono- and bidentate phosphitesand phosphines (Fig. 2) for use both in organic and alternativereaction media. The imperative need to develop active andselective systems with the possibility of catalyst recycling,and by the fact that there are no reviews covering thissubject, detailed examples of the preparation of functionalisedligands for potential use in alternative reaction media, such as

Fig. 1 Structures of (R)- and (S)-BINOL and partially hydrogenated H8-BINOL.

Fig. 2 General structures of chiral binaphthyl based phosphite and phosphineligands.

Rui M. B. Carrilho

Rui M. B. Carrilho obtained adegree in Chemistry, fromUniversity of Coimbra in 2006and received his Master diplomain Advanced Chemistry in 2008,from the same University, in Prof.Mariette M. Pereira’s group. He iscurrently finishing his PhD inSupramolecular Chemistry,focused on the synthesis ofphosphorus ligands anddevelopment of organometalliccomplexes for homogeneouscatalysis, with Prof. Mariette M.

Pereira and with Prof. Laszlo Kollar (University of Pecs). He is theauthor of 6 peer-reviewed papers in international journals and 1book chapter. His current research interests are the design andsynthesis of phosphorus ligands, organometallic chemistry,immobilization of metal catalysts in solid supports andhomogeneous/heterogeneous catalysis.

Artur R. Abreu

Artur R. Abreu received hisChemistry diploma from theNew University of Lisbon (2004)and his PhD in SupramolecularChemistry in 2010, from theUniversity of Coimbra,supervised by Prof. Dr MariettePereira and co-supervised by Prof.Dr Joan Carles Bayon (UniversityAutonoma of Barcelona). Duringhis PhD he developed newsynthetic strategies for thepreparation of bis-BINOL andBis-MOP type ligands. In 2010

he was invited to join Luzitin SA as Drug SubstanceManufacturing Manager. Since 2010 he has also been InvitedAuxiliary Professor at the University of Coimbra, and his currentresearch interests are tetrapyrrolic macrocycle and organometalliccomplex design for biological applications and homogeneouscatalysis. He has published ca. 20 peer-reviewed papers ininternational journals and 1 book chapter.

Review Article Chem Soc Rev

Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02

. View Article Online



fluorinated solvents, supercritical CO2, ionic liquids and water,are also focused.

2. Phosphite ligands

Phosphite ligands are extremely attractive compounds as theyrepresent a noteworthy breakthrough in the development ofseveral asymmetric catalytic reactions.13 It is well known thatphosphites are, in general, easy to prepare from readily avail-able alcohols and present lower sensitivity to air and to otheroxidising agents when compared with phosphines. Althoughthey have low stability against nucleophiles, bulky aryl phos-phites are less prone to decomposition reactions such ashydrolysis and alcoholysis.

2.1. Monophosphites

For more than three decades, the attention on the design andsynthesis of chiral phosphorus ligands has been predominantlyfocused on bidentate chelating P-donor ligands with C2-symmetry,which was considered as a prerequisite for efficient asymmetricinduction. However, in the last decade, the growing interest inchiral monodentate phosphorus ligands has emerged due to theirexcellent performance in several catalytic asymmetric reactions,mainly in hydrogenation14 and allylic substitutions.15 The straight-forward synthesis and easy structural modifications of chiralmonodentate ligands are highly advantageous because they allow

simple approaches in finding the most suitable ligand for aparticular catalytic asymmetric transformation.

In recent years, a large library of binaphthyl based monophos-phite ligands has been developed, in which the phosphorusatom is incorporated into a seven-membered ring. Several mod-ifications in ligand design have been performed, most of whichby varying the alcohol unit R and/or by introducing differentsubstituents at the ortho positions of the binaphthyl moiety(Fig. 3).

The preparation of monophosphite ligands follows a generaltwo-step procedure that includes the reaction of enantio-merically pure BINOL with PCl3 in the presence of base, to forma phosphochloridite. The desired alcohol and a base (generally,triethylamine) are then added to the phosphochloridite solutionto obtain the chiral monophosphite 1 (Fig. 4, route A). Anotherapproach involves the previous treatment of the mono-alcoholwith PCl3, in the presence of base, to give the desired dichloro-phosphite, followed by its reaction with enantiomerically pureBINOL and base (Fig. 4, route B). Nevertheless, the first approachtends to be more efficient, since the key of the process is thesynthesis of chlorophosphite intermediates, where mixtures oftrisubstituted or monosubstituted phosphorus derivatives canbe additionally formed.

Reetz16–18 established the starting point for the development ofmonodentate phosphite ligands. The syntheses of numerousbinaphthyl-based phosphite ligands of type 1 (Fig. 4) have beenreported, using a diversity of achiral or chiral alcohols, with linearor cyclic alkyl and aryl chains. Their application in rhodium-catalysed hydrogenation reactions has achieved enantioselectivitiesup to 98%, depending on either the R substituent or the substratestructure. Following the standard route A strategy (Fig. 4), thesynthesis of monophosphites containing a stereogenic phosphoruscentre has also been performed, through the coupling of an ortho-substituted binaphthyl19 phosphochloridite with isopropyl alco-hol.20 The corresponding phosphite 2 was obtained in 79%global yield, with a diastereomeric ratio (S,RP : S,SP) of approxi-mately 4 : 1 (Fig. 5); however without diastereomer separation.Fig. 3 General structure of BINOL based monophosphite ligands.

Fig. 4 General synthetic routes for BINOL based monophosphite ligands.

Chem Soc Rev Review Article

Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




Gennari and Piarulli21 reported the synthesis of a series ofmethoxyaryl and methoxybenzyl-based phosphites, throughboth possible synthetic strategies depicted in Fig. 4. In the caseof substituted benzyl derivatives, BINOL (or H8-BINOL) wastreated with PCl3 in the presence of a catalytic amount ofN-methyl-2-pyrrolidone (NMP) to give the correspondingbinaphthyl phosphochloridite (Fig. 4, route A), which was thenreacted with benzyl alcohols in the presence of triethylamine toafford the monophosphites 3 and 4 (Fig. 6), in 36–74% isolatedyields. On the other hand, the preparation of methoxyphenylbased monophosphites involved the treatment of methoxy-substituted phenols with PCl3, followed by the addition ofenantiopure BINOL (Fig. 4, route B) in the presence of triethyl-amine, affording monophosphites 5 (Fig. 6) in 17–64% yields.Mixtures of these ligands were investigated in the formation ofnon-covalent supramolecular bidentate rhodium complexes,wherein cooperative synergetic effects were proved by an excel-lent catalytic enantiodiscrimination in the hydrogenation of

acrylic acid derivatives (up to 99% ee), using appropriatecombinations.21

Natural synthons constitute valuable building blocks for thepreparation of chiral ligands. Thus, distinct families ofbinaphthyl monophosphite ligands based on diverse types ofnaturally occurring chiral groups have been developed, such asterpene,22 steroid23,24 or sugar derivatives.25–27 Bruneau28

described the synthesis of L-(�)-menthol-derived monophos-phites through the reaction of (1R,2S,5R)-(�)-menthyl dichloro-phosphite with racemic 1,10-bi-2-naphthol (Fig. 4, route B),yielding the diastereomeric mixture of phosphites 6 and 7 in96% yield (Fig. 7), easily separable by fractional crystallisation. Inaddition, Iuliano23,24 reported the synthesis of cholestanederived monophosphite ligands 8 and 9 (Fig. 7), involving thecoupling of (R)- or (S)-binaphthyl phosphochloridite with deoxy-cholic acid derivatives in 60–65% yields (Fig. 4, route A). Aheadof the efficient applications in asymmetric hydrogenation reac-tions, these steroid-based monophosphites also showed highlevels of asymmetric induction in the 1,4-addition of dialkylzincto cyclic enones, namely in the synthesis of (�)-(R)-muscone,with 63% ee.

Reetz25 and Zheng27,29 have independently developed aseries of binaphthyl monophosphite ligands, derived fromD-(+)-fructose, D-(+)-glucose and D-mannitol (Fig. 8). The dichloro-phosphite intermediates were prepared through the desiredsugar-based alcohols phosphorylation with PCl3, followed bythe reaction with BINOL or H8-BINOL30 producing the desiredmonophosphite ligands 10–17 with yields varying from 44% to 96%(Fig. 8). It should be mentioned that rhodium complexes of thesesugar derived monophosphites have been successfully applied inthe asymmetric hydrogenation of several substrates, such as alkylsubstituted acrylates, enamides, a- and b-dehydroamino acidesters, wherein remarkable enantioselectivities have been achieved(up to 99% ee).23–28

In order to prepare sterically congested ligands, which areknown to be more resistant to oxidative decomposition, Lyubi-mov31–33 reported the synthesis of carborane-containing mono-phosphites 18–20 (Fig. 9) in 78–95% yields, from ortho- andmeta-9-hydroxy-dicarba-closo-dodecarboranes and binaphthyl

Fig. 5 Synthesis of diastereomeric monophosphites with P-stereogenic centre.

Fig. 6 Substituted-benzyl and phenyl monophosphite ligands.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




phosphochloridite (Fig. 4, route A). Both BINOL and H8-BINOL-based monophosphites have induced excellent enantioselectivity(up to 99% ee) in asymmetric rhodium-catalysed hydrogenationof dimethyl itaconate.

With the aim of achieving recyclable catalysts for enantio-selective hydrogenation reactions, the synthesis of polymer-supported binaphthyl-based monophosphite ligands 21–24 hasbeen described by reacting binaphthyl phosphochloridite with theappropriate polymer-supported alcohols, using trioctylamine (21,23 and 24) or triethylamine (22) as base. The use of trioctylamine

was essential for an easy separation of polymer supported mono-phosphites as hydrochloride salts (Fig. 10).34,35 The rhodiumcomplexes of these ligands have formed highly enantioselectivecatalysts in the hydrogenation of enamides and b-dehydroaminoacid esters (up to 99% ee). Furthermore, the polymer supportedmonophosphites were easily separated from the reaction mixtureand conveniently recycled, preserving the catalytic activity andenantioselectivity after four runs.35

In order to develop efficient catalysts for asymmetric allylicsubstitution reactions and for the arylation of aldehydes,

Fig. 7 L-(�)-Menthol and deoxycholic acid derived monophosphite ligands.

Fig. 8 Illustrative examples of carbohydrate-derived monophosphite ligands.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




Lyubimov36 reported the synthesis of monodentate phosphiteligands, bearing two binaphthyl units attached to the phos-phorus atom, starting from (R)-BINOL, (R)-H8-BINOL or (R)-H8-3,30-dibromo-BINOL. Ligands 25 and 27 have been readilysynthesised, in one step, from the corresponding binaphthylprecursors in ca. 90% yields (Fig. 11). Remarkably, the synthesisdid not involve the isolation of any phosphochloridite ordichlorophosphite as intermediates, but proceeded directly,through the dropwise addition of 0.5 equivalents of PCl3 toa solution of the appropriate (R)-dihydroxybinaphthyl and

1.5 equivalents of triethylamine. The crude products did notrequire chromatographic purification and demonstrated enoughstability to tolerate washing with aqueous NaHCO3. Trimethyl-silylated binaphthyl phosphite 26 was easily obtained by thereaction of 25 with N,O-bis(trimethylsilyl)acetamide (BSA)(Fig. 11).

The same authors reported the synthesis of phosphite ligands28 (Fig. 12), containing dissymmetric BINOL fragments,37,38

through the phosphorylation of differently monoprotectedBINOL derivatives. These ligands have induced remarkable

Fig. 9 Carboranyl-based monophosphites.

Fig. 10 Polymer-supported monophosphite ligands.

Fig. 11 One-pot synthesis of monophosphite ligands bearing two binaphthyl units.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




enantioselectivities in palladium-catalysed allylic substitutionreactions.37

Zhou39 reported the synthesis of a monodentate phosphitederived from spirobiindane backbone 29 (Fig. 12), carried outby the reaction of (R)-1,10-spirobiindane-7,7 0-diol with PCl3, andsubsequent reaction with the respective lithium BINOLate.Excellent enantiomeric excesses were obtained in the hydro-vinylation of styrene, using palladium complexes of this ligand.

In order to perform a match/mis-match study in Cu-catalysed1,4-conjugate additions of diethyl zinc, Yee40 developed a seriesof modulated monophosphite ligands 30–33 (Fig. 12), whichconsisted of two chiral biaryl elements with different scaffoldconfigurations. These ligands were prepared in moderate yields(50–60%), from the respective carboxylic acid esters and appro-priate BINOL or H8-BINOL phosphochloridites, in the presenceof triethylamine.

Recently, C3-symmetry compounds have attracted particularinterest due to their potential use in several areas of chemistry,such as asymmetric catalysis, molecular recognition andnanoarchitecture.41,42 In this context, Reetz43 and Pereira44,45

have independently followed this novel concept in ligandchirality, by developing the synthesis of the first symmetricallysubstituted tris-binaphthyl monophosphite ligands with helicaltriskelion structures (Fig. 13).

The synthetic strategy reported by Reetz43 consisted of thereaction of (R) or (S)-BINOL with acyl halides, affording BINOLmono-ester derivatives. Subsequent phosphorylation with PCl3

gave monophosphite ligands 34 in 90% overall yields (Fig. 13A).When used as ligand in the rhodium-catalysed hydrogenationof homoallylic alcohols, the sterically hindered adamantanoylderived helical ligand 34b led to excellent enantioselectivities(up to 98% ee). In contrast, the more flexible and less sterically

congested phenyl analogue 34a formed rhodium catalysts withpoor enantiodiscrimination in the same reaction.43

Pereira and Bayon44 reported a slightly different approach,which involved the mono-etherification reactions of (R) or(S)-BINOL with primary, secondary or tertiary alcohols, carried outin the presence of triphenylphosphine and diethyl azodicarboxylate(DEAD), via Mitsunobu reaction.46 Three equivalents of theBINOL mono-ethers were then reacted with PCl3 in triethyl-amine, which was simultaneously used as base and solvent,producing a set of tris(20-alkoxy-1,10-binaphthyl-2-yl)phosphites35, in 76–83% overall yields (Fig. 13B).44,45 These ligandshave been successfully applied in catalytic carbonylation reac-tions, namely in the Rh-catalysed hydroformylation of substi-tuted aryl olefins45 and Pd-catalysed double carbonylation of1-iodocyclohexene.47

2.2. Diphosphites

Despite the recent interest in monophosphite ligands,48 diphos-phites constituted, over the years, a class of bidentate ligandswith greater versatility in a large number of enantioselectivecatalytic reactions.13

At the beginning of the 1990s, Baker and Pringle49 reportedthe first synthesis of diphosphite ligand 36 containing threebinaphthyl units, through the one-step reaction of PCl3 with1.5 equivalents of (R)-BINOL and triethylamine (Fig. 14).

Since Pringle’s pioneering work, significant improvementsin synthetic approaches have been developed, leading to thepreparation of wide libraries of binaphthyl-based diphosphites.In general, these syntheses may follow one of the two syntheticstrategies presented in Fig. 15.

The first approach involves the reaction of enantiomericallypure BINOL with PCl3, in the presence of a base, which leads to

Fig. 12 Monophosphite ligands bearing different biaryl scaffolds.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




the formation of binaphthyl phosphochloridite. The subse-quent in situ addition of the desired diol affords diphosphiteligands in which both oxygen atoms of each binaphthyl unit arebonded to the same phosphorus atom (Fig. 15, route A).

A different two-step approach involves the previous treat-ment of PCl3 with two equivalents of a given alcohol (or oneequivalent of a diol) to give the respective phosphochloridite,which is then reacted with enantiomerically pure BINOL inbasic media, to furnish the desired diphosphite ligands inwhich each oxygen atom of the binaphthyl backbone is bondedto different phosphorus atoms (Fig. 15, route B).

As the great majority of binaphthyl-based diphosphitesdescribed in the literature involve the synthetic approachesdescribed in Fig. 15, some selected examples will be men-tioned, specifying for each one the most relevant details about

the particular reagents and/or reaction conditions, as well asmain applications in catalysis.

Chan50,51 and Bakos52 reported the synthesis of a series ofC2-symmetric diphosphites 37–42 (Fig. 16) through reaction ofenantiopure BINOL phosphochloridites with several aryl diols,including the optically pure BINOL and H8-BINOL (Fig. 15,route A). Ligands 37–41 were applied in enantioselective copper-catalysed conjugate additions of diethyl zinc to enones (up to90% ee),53 and in nickel-catalysed hydrocyanation of olefins (upto 90% ee).54 Furthermore, the diastereomeric ligands 42a–b wereevaluated in rhodium and platinum-catalysed hydroformyla-tion of styrene, in which a systematic study of cooperativechirality between the different binaphthyl scaffolds wasperformed.52

The preparation of binaphthyl diphosphite ligands withhomochiral pentane-2,4-diol spacers has also been describedby Kamer55 and Bakos.56,57 A set of diastereomeric diphosphites43 were synthesised, starting from (2R,4R)- or (2S,4S)-pentane-2,4-diol and 3,30-bis(trialkylsilyl)-2,20-binaphthol phosphoro-chloridites (Fig. 15, route A), in moderate to excellent yields(47–96%). These diphosphites have been used to study theeffects of cooperative chirality in the asymmetric hydroformyla-tion of styrene, in which the highest enantioselectivity (87% ee)was induced by the ligand derived from (2R,4R)-pentane-2,4-dioland (S)-BINOL. It should be noted that diphosphite 44 contain-ing two binaphthyl fragments with different axial chiralitieswas synthesised in two steps, via the addition of (R)-3,30-bis(trimethylsilyl)-2,20-binaphthol phosphochloridite to (2R,4R)-pentane-2,4-diol, affording the mono-substituted phosphoruscompound, which was isolated from the reaction mixture and

Fig. 13 Synthetic routes for tris-binaphthyl monophosphite ligands.

Fig. 14 (R)-BINOL based diphosphite containing three binaphthyl units.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




subsequently reacted with (S)-binaphthyl phosphochloridite(Fig. 17).55

Using the standard methodology (Fig. 15, route A), Chan58

reported the preparation of spiro[4.4]nonane-1,6-diol deriveddiastereomeric diphosphites 45 (Fig. 18) in 62% isolated yield,which were applied in the asymmetric rhodium-catalysedhydroformylation of styrene derivatives, although achievinglow enantioselectivity (up to 24% ee).

Similarly, Reetz59 described the synthesis of both (R,R) and (S,S)diastereomeric diphosphites 46 derived from 1,4 : 3,6-dianhydro-D-mannitol (Fig. 18), in 96% and 87% yields, respectively. Theligands were evaluated in the Rh-catalysed hydrogenation ofdimethyl itaconate, where a synergistic effect was observedbetween the chirality of the diol and the axial chirality of thebinaphthyl backbone, i.e. ligand 46a with a (R,R) configuration,was demonstrated to form a more active and also more enantio-selective catalytic system (95% ee) than that obtained with the (S,S)counterpart 46b (88% ee).

Claver and co-workers60–67 reported the synthesis of a widelibrary of modular binaphthyl-based diphosphites derived fromcarbohydrate backbones, such as D-(+)-xylose, D-(+)-glucose,

D-glucosamine and D-glucitol derivatives, through reactionbetween the desired sugar-based diol and (R)- or (S)-BINOLphosphochloridite (Fig. 15, route A), affording diphosphites47–56 (Fig. 19).

Wang and Chan also focused their interest on the synthesisof a set of sugar-based diphosphite ligands derived from phenyl3,6-anhydro-b-D-glucopyranoside, phenyl 3,6-anhydro-b-D-galacto-pyranoside,68–70 methyl 3,6-anhydro-a-D-glucopyranoside71 and1,2 : 5,6-di-O-cyclohexylidene-D-mannitol72,73 57–60 (Fig. 19), throughreaction of the respective carbohydrate precursors and the desiredBINOL or H8-BINOL phosphochloridites, in the presence oftriethylamine and N,N-dimethylaminopyridine (DMAP). It shouldbe mentioned that, in general, these sugar-based diphosphiteligands were demonstrated to be remarkably stable duringchromatographic purification steps and air-stable in the solidstate. Moreover, these large families of diphosphite ligandsderived from carbohydrate backbones have been applied inmultiple asymmetric catalytic reactions, namely in Rh-catalysedhydrogenation and hydroformylation reactions, Pd-catalysedallylic substitutions and Cu-catalysed conjugate additions,68–71

giving particularly remarkable results in the hydrogenation of

Fig. 16 Binaphthyl diphosphite ligands based on aryl diols.

Fig. 15 General strategies for synthesis of binaphthyl based diphosphites.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




N-acetamidoacrylate (ee’s up to 99%)61 and in the hydroformyla-tion of styrene (regioselectivity up to 98% and ee’s up to 83%).66

Using the standard procedures, Reetz74 described the synth-esis of a set of inexpensive chiral diphosphites 61 and 62 in75–95% yields (Fig. 20), containing variable size achiral spacers(including polymeric PEG400), linking the two binaphthylunits, through reaction of the desired diol with enantiomeri-cally pure (R) or (S)-binaphthyl phosphochloridite, under basicconditions. As a model reaction for testing the performance ofthese ligands, the authors have chosen the asymmetric rhodium-catalysed hydrogenation of dimethyl itaconate, in which theconversions and enantioselectivity were remarkably higher usinglonger achiral backbones (up to 99% ee).

Although less frequent, there are several examples of thesynthesis of diphosphites bearing only one binaphthyl unit, inwhich each oxygen atom of the BINOL backbone is bonded to adifferent phosphorus atom (Fig. 15, route B). For example,Bakos52,75 described the preparation of diastereomeric diphos-phite ligands containing chiral 1,3,2-dioxaphosphorinane moi-eties 63 (Fig. 21), through reaction of the racemic BINOL with(4R,6R)- or (4S,6S)-2-chloro-4,6-dimethyl-1,3,2-dioxaphosphori-nane, previously obtained from the optically pure enantiomersof 2,4-pentanediol and PCl3, in the presence of triethylamine.The diastereomers were separated by fractional crystallisation

from acetonitrile, thereby providing a good example of a self-resolving chiral diphosphite where the chirality in terminalgroups was used to resolve the binaphthyl axial chirality.Similarly, diastereomers 64 based on enantiopure (R)- and(S)-H8-BINOL (Fig. 21) were also synthesised.

Other examples of diphosphite ligands prepared via B(Fig. 15) were illustrated by Vogt,76 who synthesised a libraryof diphosphites based on 3,30-substituted binaphthyl deriva-tives and ortho-substituted phenols. The desired ligands 65(Fig. 21) were obtained by the reaction of two equivalents ofortho-substituted phenols with PCl3 in the presence of triethyl-amine, and subsequent addition of 0.5 equivalents of thedesired (R)-BINOL derivative. This series of diphosphite ligandswas evaluated in the asymmetric nickel-catalysed hydrocyana-tion of olefins, achieving remarkable enantioselectivities (up to86% ee, in the hydrocyanation of 1,3-cyclohexadiene).

Lyubimov,77 described the first synthesis of carboranyldiphosphites, using both A and B synthetic routes described inFig. 15. Diphosphites 66 and 67 were obtained through phosphory-lation of the corresponding ortho- or meta-carboranediols withenantiomerically pure binaphthyl phosphochloridites. A differentapproach was followed for the preparation of diphosphite ligand68, through the phosphorylation of ortho-carboranediol withPCl3 and subsequent reaction with enantiomerically pure (R) or

Fig. 17 Synthesis of (2R,4R)-pentane-2,4-diol derived diphosphite, bearing two binaphthyl units with (R,S) chirality.

Fig. 18 Structure of diphosphite ligands derived from spiro[4.4]nonane-1,6-diol and 1,4:3,6-dianhydro-D-mannitol.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




(S)-BINOL. Similar approaches have been followed by the sameauthor for the synthesis of the first [2.2]paracyclophane-baseddiphosphite ligands 69 and 70, bearing two or one binaphthylunits respectively (Fig. 22).78

Furthermore, Freixa and Bayon79,80 have described the firstexample of large chelating ring diphosphites, bearing two

binaphthyl units linked by a 2-hydroxypropyl isophthalate spacer.The respective (R)- and (S)-phthaBinPhos 71 (Fig. 23) were preparedby reaction of (2S)-hydroxypropyl isophthalate with (R)- or (S)-BINOLphosphochloridites, in the presence of triethylamine (Fig. 15,route A). The two (R) and (S)-diastereomeric phosphite ligands haveinduced dissimilar enantioselectivities in the rhodium-catalysedhydroformylation of styrene (62% ee vs. 11% ee, respectively), beinga paradigmatic example of the matching–mismatching effect shownby remarkably different tendencies to form chelating species.

Pereira and Peixoto81 have recently extended the developmentof this type of ligands, through the preparation of ditopic(R)-BINOL-based phosphites, containing pyridine derivatives linkingtwo binaphthyl fragments. The 2,6-bis(2-hydroxyethyl)pyridine-dicarboxamide, previously synthesised from 2,6-dimethyl-pyridinedicarboxilate and 2-aminoethanol, the commercially

Fig. 19 Diphosphite ligands based on carbohydrate backbones.

Fig. 20 Chiral binaphthyl diphosphites containing achiral polymeric spacers.

Fig. 21 Binaphthyl based diphosphite ligands derived from 1,3,2-dioxaphosphorinane and from ortho-substituted phenols.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




available 2,6-dihydroxypyridine hydrochloride and 2,6-bis(hydroxy-methyl)pyridine were reacted with (R)-binaphthyl phosphochlor-idite (Fig. 15, route A), in the presence of a large excess oftriethylamine, yielding the diphosphite ligands 72, 73 and 74(Fig. 23), respectively.

In a different approach, the same authors developed the syn-thesis of diphosphites 75, containing alkyl ether spacers linkingtwo binaphthyl fragments.81 These were synthesised by reaction of(1R,100R)-2 0,200-[propane-1,3-diyl-bis(oxy)]di-1,10-binaphthyl-2-olor (1R,100R)-20,200-[2,2-dimethylpropane-1,3-diyl-bis(oxy)]di-1,1 0-binaphthyl-2-ol,82 with pyrocathecol phosphochloridite (Fig. 15,route B), using triethylamine as base (Fig. 24).83

Following the concept of macromolecular chemistry, Vogt84

reported the synthesis of a family of bidentate phosphites

derived from incompletely condensed silsesquioxane back-bones and enantiopure BINOL. The reaction of azeotropicallydried silsesquioxane disilanol derivatives with (R)-binaphthylphosphochloridite (Fig. 15, route A), in toluene and triethylamine,afforded the desired diphosphite ligands 76 (Fig. 25) in very goodyields (79–92%). These nanosized ligands have been applied inthe rhodium-catalysed asymmetric hydroformylation of vinylacetate and hydrogenation of amidoacrylates achieving highactivities and moderate enantioselectivities.

Moreover, Semeril and Matt85,86 reported the synthesis ofcalixarene based diphosphites 77 (Fig. 25), bearing various sidegroups. The preparation of these macromolecular ligands wasaccomplished by double deprotonation of the appropriatedistilled O-dialkylated precursor with sodium hydride, followed

Fig. 22 Synthesis of carboranyl and [2.2] paracyclophane-based diphosphites.

Fig. 23 P,O and P,N large chelating ring diphosphites.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




by reaction with (S)- or (R)-binaphthyl phosphochloridite intoluene (Fig. 15, route A). The synthesis showed a strongdependence on the steric hindrance of the calixarene R2 sidegroup, with yields varying from 14 to 75%. Remarkably, thesecalix-diphosphites provided the first examples of hemisphericrhodium chelators able to efficiently promote olefin hydro-formylation towards the formation of linear products, evenusing aryl olefins as substrates.

3. Phosphine ligands

Among the numerous examples of phosphine ligands reportedso far,10 binaphthyl based phosphines emerged as a class ofligands with great relevance for the development of new organo-metallic compounds with applications in asymmetric catalysis.87

Phosphine ligands are of great interest due to their resistance tohydrolysis and easier purification when compared to phosphites,despite their vulnerability to oxidation.

3.1. Monophosphines

Binaphthyl-based monophosphines became recognised ashighly efficient ligands in a number of enantioselective transition-metal catalysed reactions, namely in asymmetric hydrogenation,11

palladium-catalysed asymmetric hydrosilylation of olefins,88

asymmetric reactions via p-allylpalladium intermediates, suchas reduction of allylic esters with formic acid89,90 and enantio-selective addition of diethyl zinc to enones.91

The foremost examples of optically active monodentatephosphines possessing a binaphthyl skeleton are 2-(diphenyl-phosphino)-1,10-binaphthyl MOP-type ligands (Fig. 26).

The synthesis of 2-(diphenylphosphino)-2 0-methoxy-1,1 0-binaphthyl 78a was first developed by Hayashi,92 through afive-step pathway that included the triflation of hydroxylgroups of BINOL, the selective monophosphinoylation of 1,10-binaphthyl-2,2 0-ditriflate, hydrolysis of the remaining triflate,subsequent methylation to give the 2-diphenylphosphinoyl-2 0-methoxy-1,10-binaphthyl derivative and finally reduction with

Fig. 24 Synthesis of propyl ether linked bis-binaphthyl diphosphites.

Fig. 25 Silsesquioxane and calixarene based diphosphites.

Fig. 26 General structure of (R) and (S)-MOP-type phosphines.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




trichlorosilane in the presence of base, achieving MeO-MOP78a (Fig. 27). In parallel, Strycker used a similar synthetic strategyfor the preparation of 2-(dimethylphosphino)-20-methoxy-1,10-binaphthyl 78b with 73% overall yield.93

Using analogous synthetic methodologies, libraries of20-substituted binaphthyl MOP derivatives has been developed,through the introduction of diverse alkoxy, alkyl, cyano, methoxy-carbonyl, carboxy and aryl groups (Fig. 26),94 as well as thebiphenanthryl analogue, MOP-phen 79 (Fig. 27).92

Zeng and Yang reported an alternative synthetic route of(R)-MeO-MOP 78, in which enantiopure (R)-BINOL was firsttransformed into its monomethyl ether via Mitsunobu reac-tion46 in the presence of diethyl azodicarboxylate (DEAD) andtriphenylphosphine, followed by reaction with triflic anhydride.95

The palladium/xantphos-catalysed C–P coupling of the resultingtriflate with diphenylphosphine oxide and subsequent reductionwith trichlorosilane, produced the desired (R)-MeO-MOP 78 in44% overall yield (Fig. 28).

MOP ligands possess the advantage of being easily fine-tuned, by introduction of suitable substituents at both 2 and20-positions of the 1,10-binaphthyl skeleton according to eachcatalytic reaction required specificity, thus enhancing theirutility in a wide range of processes.92 For instance, palladium-catalysed hydrosilylation reactions are typical examples whereMOP-type derivatives have been considered as the ligands ofchoice, providing high enantioselectivities in asymmetric hydro-silylation of aryl, cyclic or alkyl-substituted terminal olefins.

A further approach for the preparation of aryl MOP phos-phines was reported by Hayashi,96,97 based on the asymmetricKumada98 cross-coupling of dinaphthothiophene with anarylmagnesium reagent, in the presence of chiral inducingoxazoline-phosphine ligand (i-Pr-phox), followed by alkylationof the thiol and subsequent oxidation with meta-chloroperoxy-benzoic acid (mCPBA). Finally, the resulting methylsulfoxidewas reacted with ethylmagnesium bromide and diphenylphos-phine chloride to give phenyl-MOP phosphine 80 in 40% yieldand 19% of optical purity (Fig. 29).

Aiming at the synthesis of sterically hindered 20-aryl-1,10-binaphthyl phosphines, Putala99 reported two distinct alternativesynthetic strategies (Fig. 30). The first methodology started withthe selective mono-acetylation of (R)-1,10-binaphthyl-2,20-diamine(BINAM), followed by substitution of the second amino group byan iodide via diazotization and subsequent treatment withpotassium iodide. Arylation of the resulting mono-iodide deriva-tive with ortho-methoxyphenylboronic acid, followed by deprotec-tion in acidic medium afforded the corresponding arylatedmonoamine. Next, the remaining amino group was replaced byan iodide via diazotization and finally, after treatment withn-butyllithium, followed by phosphinylation the anisyl-MOPphosphine 81 was obtained in 15% overall yield (Fig. 30A).

The second approach involved the Pd-catalysed Negishicoupling100 of enantiomerically pure (R)-2,20-dibromo-1,10-binaphthyl with an arylzinc bromide. The subsequent lithiationof the monoarylated bromo-compound, followed by couplingwith the desired chlorophosphines, provided diphenylphos-phanyl 81 or dicyclohexylphosphanyl 82 MOP analogues inca. 50% overall yield, whereas the dicyclohexyl derivative wasisolated as a borohydride adduct 82a (Fig. 30B).99

The modulation of the steric and electronic properties of MOP-type phosphine ligands was developed through the introductionof electron-rich substituents on the phosphorus atom.101,102

Buchwald reported the preparation of a series of 2-dialkylphos-phino-20-alkoxy-1,10-binaphthyl ligands 83 based on Hayashi’sstandard methodology92 in up to 61% overall yields (Fig. 31).These ligands were applied in palladium-catalysed asymmetrichydroesterification of vinylarenes103 and in palladium-catalysedasymmetric arylation of ketone enolates.104

Fig. 27 Synthesis of MeO-MOP type phosphines.

Fig. 28 Alternative synthetic route for (R)-MeO-MOP.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




Recently, Higham reported the synthesis of a thermal andair stable MOP type phosphine ligand containing a rigidcyclopropyl ring at the phosphorous atom, achieving highenantiomeric excess on the palladium-catalysed asymmetrichydrosilylation of styrene.105

Moreover, two different strategies were reported by Zhang106

for the preparation of bulky and electron-rich 2-dialkylphos-phino-20-alkoxy-1,10-binaphthyl phosphines. The first oneinvolved the dehydration of BINOL with an HY zeolite to formbinaphthofuran. The subsequent reductive ring opening withmetallic lithium afforded the respective dilithium salt, whichwas then reacted with chlorodicyclohexyl phosphine to formthe 2-dicyclohexylphosphino-2 0-hydroxybinaphthyl derivative.Due to its vulnerability to oxidation, the latter was immediatelyoxidised with hydrogen peroxide. Since the resulting phosphineoxide was insoluble in most organic solvents, it was treatedwith sodium hydride to achieve a soluble sodium salt. Finally,alkylation took place (with Me2SO4, i-PrBr or BnCl), followed byreduction with trichlorosilane, in basic media, yielding thedesired 2-dicyclohexylphosphino-20-alkoxy-1,10-binaphthyl ligands

Fig. 29 Dinaphthothiophene based synthetic route for Ph-MOP.

Fig. 30 Two different synthetic approaches for anisyl-MOP analogues.

Fig. 31 General structure of 2-dialkylphosphino-2 0-alkoxy-1,10-binaphthylderivatives.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




84 in overall yields up to 44% (Fig. 32A). In the second syntheticapproach, direct reaction of di-lithium salt with di-tert-butylchlorophosphine using a catalytic amount of CuI produced2-di-tert-butylphosphino-20-hydroxylbinaphthyl, which was stableenough to be directly alkylated with Me2SO4, i-PrBr, or BnCl toafford 2-di-tert-butylphosphino-20-alkoxy-1,10-binaphthyl ligands85, in 50% yield (Fig. 32B).

Using standard procedures, RajanBabu107 used 3-methyland 3-phenyl substituted binaphthyl derivatives for the synth-esis of modified MOP-type ligands to study working models forasymmetric induction in nickel-catalysed hydrovinylation reac-tions. The synthetic strategies previously reported by Hayashi92

were used to prepare the desired MOP-type phosphines 86 in36% after 5 steps (Fig. 33).

The same author also reported the synthesis of a structurallyrelated MOP-phospholane 87, bearing a chiral 1-(2,5-dimethyl-phospholano) substituent at the 2-position of the binaphthylscaffold, through the reduction of a phosphonate derivative

with aluminium lithium hydride, followed by reaction with acyclic chiral sulfate in the presence of KH (Fig. 33).107

Gladiali reported the synthesis of MOP type ligands bearingan alkyl thioether group in the 20 position of the binaphthylbackbone.108 Later on, Hagiwara expanded this family throughthe synthesis of a set of 20-aryl thioether MOP type ligands.Their palladium complexes revealed to be active and stereo-selective in the asymmetric allylic alkylation of indole.109,110

The incorporation of additional chirality at the phosphorusatom111,112 may lead to the improvement of the ligand’s chiralinduction in several enantioselective catalytic reactions. In thiscontext, Gilheany113 described a synthetic route for P-chiro-genic MOP analogues through the palladium/dppe-catalysedcross-coupling of (R)-BINOL bis-triflate with methylphenylphos-phine oxide in the presence of diisopropylethylamine (DIPEA),which afforded a 1 : 1 mixture of diastereomeric phosphineoxides. After separation by chromatographic methods, in acombined yield of 79%, both diastereomers were hydrolysed

Fig. 32 Synthetic routes for dialkylphosphino-2 0-alkoxy-1,10-binaphthyl ligands.

Fig. 33 30-Substituted MOP phosphines and 2-phospholano-OMe-MOP ligand.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




and alkylated in good yields and, finally, a stereospecificreduction using hexachlorodisilane (HCDS) was performed toafford the diastereomerically pure P-chirogenic phosphineligands 88 (Fig. 34, route A). It should be noted that otherreduction procedures (HSiCl3/Et3N and LiAlH4/MeOTf) led tothe complete or partial epimerisation at the phosphorus atom.

Lemaire114 described an identical approach, with the exceptionof the tertiary phosphine oxide reduction step, which was per-formed using an association of tetramethyldisiloxane (TMDS) andtitanium(IV) isopropoxide, leading to the formation of P-chirogenicphosphines 89 in overall yields up to 35% (Fig. 34, route A).

A different synthetic alternative was applied to a number ofother P-stereogenic MOP analogues with different P-substitu-ents.115–117 This method proceeded via methylation of mono-triflated (R)-BINOL and direct coupling of the resulting methoxytriflate with a secondary phosphine using the nickel/dppecatalyst to give a mixture of diastereomers, which were sepa-rated as the protected phosphine boranes by flash chromato-graphy. The borane protecting groups were then removed bythe addition of a base to give the desired diastereomericallypure phosphine products 90 (Fig. 34, route B). P-stereogenicMOP analogues 89 were employed as ligands in palladium-catalysed hydrosilylation of styrene, affording the corre-sponding alcohol in high yield and enantiomeric excess.The MOP analogues 90 were applied in rhodium-catalysed

asymmetric addition of boronic acids to aldehydes, whereinthe authors have not been able to improve previous resultsobtained with MeO-MOP.117

Buchwald expanded the family of P-chiral monophosphineligands synthesizing a set of 2-(alkylphenylphosphine)-2 0-(dimethylamino)-1,10-binaphthyl (MAP) compounds whichprovided up to 96% ee in palladium-catalysed asymmetricvinylation of enolates and in ketone arylation.118

The BINOL carba-analogue, 2,20-dimethyl-1,10-binaphthyl,was also demonstrated to be a relevant building block forenantioselectivity induction in asymmetric catalysis. Severalresearch groups have independently reported the synthesis ofmonodentate phosphines based on 4,5-dehydro-3H-dinaphtho-[2,1-c;10,20-e]phosphepine.119–122 Beller119 described two differentsynthetic routes: the first approach involved the double metalla-tion of 2,20-dimethylbinaphthyl with n-butyl lithium in thepresence of tetramethylethylenediamine (TMEDA), followed byquenching with commercially available dichlorophosphines, yield-ing 91 in 60–83% yields (Fig. 35, route A). In the second route, thedouble lithiation was followed by quenching with diethylamino-dichlorophosphine. The subsequent reaction with HCl gave thecorresponding chlorophosphepine, which was reacted with severalGrignard reagents (prepared from alkyl or aryl halides), affordingall the 4,5-dehydro-3H-dinaphtho[2,1-c;10,20-e]phosphepines 91 in50–60% yields, after 2 steps (Fig. 35, route B).119

Fig. 34 Two different synthetic approaches for P-chirogenic MOP analogues.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




A different synthetic strategy, reported by Zhang,120 involvedthe lithiation of 2,20-dimethyl-1,10-binaphthyl with n-butyllithium in ether to form di-lithium salt, which was isolatedunder inert conditions and further reacted with phosphorustrichloride in hexane, yielding the chlorophosphepine deriva-tive. Chiral phosphine ligand 91c was then synthesised bynucleophilic substitution of chlorophosphepine with t-butylGrignard reagent in 12% overall yield (Fig. 35, route C).

Independently, Gladialli123 and Willis124 reported the pre-paration of dinaphthophosphole 92 containing a phospholering merged within the atropisomeric binaphthyl backbone,which could be prepared either by reaction of 3,30,4,40-tetra-hydro-1,10-binaphthyl with dichlorophenylphosphine in 25%yield (Fig. 36, route A), or from the reaction of 2,20-dibromobi-naphthyl with n-butyllithium, followed by coupling withdichlorophenylphosphine, in 80% yield (Fig. 36, route B). Inaddition, a set of P-alkyl dinaphthophospholes were synthe-sised in high yields by the second approach using the appro-priate phosphorated reagent.

Some authors have further developed the synthesis of mono-phosphine ligands combined with the alkene functionality. Forinstance, Widhalm125 described a chiral phosphepine-olefinwith (pseudo)-C2 symmetry, the synthesis of which was achievedby deprotonation of enantiopure 4,5-dehydro-3H-dinaphtho[2,1-c;10,20-e]phosphepine borane derivative with n-BuLi, and subsequenttreatment with cinnamyl bromide. Borane deprotection with diethyl-amine furnished phosphine ligand 93 in 61% yield (Fig. 37A). Thisphosphine-alkene has acted as a chiral bidentate ligand withrhodium complexes and applied in the asymmetric conjugateadditions of arylboronic acids to cycloalkenones and 5,6-dihydro-2H-pyran-2-one, in which good yields (64–88%) and remarkableasymmetric inductions (88–98% ee) have been obtained.

More recently, Zhuang126 reported the synthesis of MOP-typephosphine-alkene ligands, through a straightforward syntheticroute, using (S)-BINOL or (S)-H8-BINOL as starting materials,where the first three steps were based on well known procedures.The key step was the coupling reaction between 2-diarylphos-phino-20-triflate-1,10-binaphthyl derivative and potassium alkenyltrifluoroborates, catalysed by Pd(PPh3)4, giving the pure phos-phine-alkene ligands 94 and 95 in overall yields up to 50%(Fig. 37B). Their application in Pd-catalysed asymmetric allylicalkylation of indoles and pyrroles with 1,3-diaryl-2-propenylacetate afforded the corresponding products in high yields andexcellent enantioselectivities (up to 98% ee).

3.2. Diphosphines

Chiral diphosphines are another important class of ligands withmultiple applications in asymmetric organometallic catalysis.127

Among them, binaphthyl based BINAP 96 (Fig. 38)127,128 and itsderivatives are paradigmatic compounds, whose transition metal

Fig. 35 Routes for 4,5-dehydro-3H-dinaphtho[2,1-c;10 ,20-e]phosphepine ligands.

Fig. 36 Two routes for the synthesis of atropisomeric dinaphthophosphole.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




complexes have been widely used as highly enantioselectivecatalytic systems in several reactions, such as the isomerisationof allylic amines129,130 and the asymmetric hydrogenation ofolefins131–136 and ketones.137–139

In general, the synthesis of enantiomerically pure BINAPligands can be achieved either by phosphination of racemicBINOL derivatives, followed by chiral resolution via recrystalli-sation in the presence of a resolving agent, or by directphosphination of enantiopure BINOL derivatives, usually viathe preparation of bis-triflated intermediates.127,128 Noyoridescribed in 1980 the first synthesis of BINAP,131 starting fromracemic BINOL, which was first transformed into the corres-ponding 2,20-dibromo-1,10-binaphthyl, using triphenylphosphi-nedibromide as a brominating agent, at high temperatures.The dibrominated compound was then submitted to lithiationwith tert-butyllithium, followed by coupling reaction withdiphenylphosphine chloride. Finally, the racemic diphosphinewas resolved via fractional recrystallisation in the presence of achiral palladium complex. The enantiopure (R)- and (S)-BINAP96 were obtained after palladium decomplexation in a reductivemedium (Fig. 39).

Some years later, the same author140 described a differentapproach, which involved the synthesis of a diphosphine oxideas the intermediate. First, a Grignard reagent was synthesisedfrom racemic 2,20-dibromo-1,10-binaphthyl and magnesium.

The subsequent reaction with diphenylphosphineoxochloridegenerated the corresponding racemic diphenylphosphinedioxide (BINAPO) in a 91% yield. The resolution of racemicBINAPO was carried out with (S)-(+)-camphorsulfonic acid(�)-dibenzoyl-tartaric acid (DBTA), followed by selective recrys-tallisation, yielding both enantiomers. Finally, the chiral (R)and (S)-BINAPO were easily reduced with trichlorosilane in abasic medium, affording both (R) and (S)-BINAP 96 in 95% yield(Fig. 40).

Since its first synthesis, BINAP has proved to be able toinduce high enantioselectivity in multiple asymmetric transi-tion-metal catalysed homogeneous reactions.127 This factexplains the great interest of several chemical industries topromote the development of alternative large scale syntheticprocedures. Two different approaches were based on the use ofenantiomerically pure BINOL as starting material (Fig. 41). In1995, Merck141,142 patented a two-step large scale synthesis ofBINAP, starting from the enantiopure BINOL bis-triflate, followedby Ni(II)/dppe-catalysed coupling with diphenylphosphinehydride, using triethylenediamine (DABCO) as base (Fig. 41,route A). The 1,2-bis(diphenylphosphino)ethane ligand (dppe)acts as an in situ reducing agent to transform Ni(II) into Ni(0)which is the active catalytic species. Monsanto143,144 developedanother synthetic strategy, differing from the Merck approach inthe phosphorus source and in the reducing agent. In this case thephosphorated agent is diphenylphosphine chloride, while zincpowder is used as a reducing agent to transform Ni(II) into Ni(0)(Fig. 41, route B).

Among the many excellent results achieved in enantio-selective catalysis using BINAP as the chiral ligand, it is worthmentioning the use of rhodium-BINAP complexes in the asym-metric isomerisation of allylic amines, with industrial applica-tion for the synthesis of L-(�)-menthol from myrcene.129

Furthermore, the hydrogenation of allylic and homoallylicalcohols has been performed with high enantioselectivity when

Fig. 37 Two approaches for the synthesis of phosphine–alkene ligands.

Fig. 38 (R)- and (S)-BINAP.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




a ruthenium/BINAP complex has been employed.145 Moreover,the Ru/BINAP-catalysed enantioselective hydrogenation ofprochiral ketones has also been accomplished, yielding thecorresponding alcohols in 90–100% ee.128

As previously mentioned, the activity and selectivity oftransition metal complexes can be modulated through severalstructural modifications of the ligand scaffold. Thus, modulation

of BINAP has been easily accomplished by the incorporation ofdifferent groups at the phosphorus atoms146–149 or through theintroduction of different substituents at the binaphthyl backbone,due to the easy structural modification inherent to aromaticcompound reactivity.127

The modulation of the phosphorus substituents is generallyperformed through the reaction between nucleophilic phos-phorus derivatives (typically, a phosphine oxide derivative) andbinaphthyl bis-triflate, in the presence of transition-metal/phosphines as catalysts.150 For example, Takeda ChemicalIndustries, Ltd have patented151,152 a synthetic process basedon the coupling of 2,20-bis(trifluoromethanesulfonyloxy)-1,1 0-binaphthyl with different diarylphosphineoxides, in thepresence of NiCl2/(dppe) and DABCO, using dimethylforma-mide as solvent, affording the desired BINAP analogues 97 in20 to 40% yields, with formation of phosphine oxide as a side-product (Fig. 42).

Furthermore, the synthesis of BINAP analogues containingheterocyclic, alkyl or cycloalkyl substituents in the phosphorusatom was described by several groups. Pregosin153 reported thesynthesis of racemic derivative 98, prepared by direct reaction of2,20-dibromo-1,10-binaphthyl with t-BuLi, followed by the additionof chlorodiisopropylphosphine in a 68% yield (Fig. 43A).

Fig. 39 Preparation of enantiopure BINAP, starting from racemic BINOL.

Fig. 40 Synthesis of enantiopure BINAP via BINAPO resolution.

Fig. 41 Merck and Monsanto synthetic approaches of enantiopure BINAP.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




Keay154 reported the synthesis of 2,20-bis(di-2-furylphosphino)-1,10-binaphthalene 98, by the reaction of 1,1-binaphthyl-2,2-diyldi-magnesium dibromide with furylphosphonyl chloride, in a 55%yield. After chiral resolution, enantiopure 99 was obtained in 70%yield (Fig. 43B). This ligand, whose phosphorus atom is less basicthan in BINAP, was successfully applied in palladium-catalysedasymmetric Heck arylation of 2,3-dihydrofuran (up to 100% conver-sion and 89% ee).

At the same time, Kumobayashi155 described the preparationof enantiopure 2,20-bis(dicyclopentylphosphino)-1,10-binaphthyl

100 through the coupling of 2,20-bis(magnesiumbromide)-1,10-binaphthyl with dicyclopentylphosphonyl chloride, followed bychiral resolution with (+)-dibenzoyltartaric acid, and finallyphosphine oxide reduction, with trichlorosilane (Fig. 43C). TheRh/100 was evaluated in the asymmetric hydrogenation of nerolto afford (S)-(�)-citronellol with high selectivity155 (99%) and70% ee, demonstrating to induce higher enantioselectivity thanBINAP complexes under similar reaction conditions156 (52% ee).

Gladiali157 reported a versatile synthetic approach for thepreparation of non-symmetric BINAP type ligands bearing

Fig. 42 Synthesis of aryl substituted phosphine BINAP analogues.

Fig. 43 Synthetic strategies for the preparation of furanyl, cyclopentyl and isopropyl BINAP analogues.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




different aryl substituents at the phosphorus atoms (Fig. 44).Their synthesis was accomplished through monophosphinoyla-tion of a bis-triflate BINOL derivative, using a Pd(OAc)2/dppbcatalyst. Then, the phosphine oxide was reduced to the corres-ponding phosphine using standard methods. Finally, the reac-tion with different phosphine hydrides in the presence of NiCl2/dppe as a catalyst, afforded the non-symmetric BINAP typeligands 101a–b. These ligands were evaluated in rhodium-catalysed hydrogenation of 2-acetamidoacrylic acid derivativesand in allylic alkylation of dimethyl malonate, where a signifi-cantly higher enantioselectivity (88% ee) was obtained withligand 101b, when compared with BINAP complexes (32% ee),under similar reaction conditions. A decade later Togni158

applied a similar synthetic methodology to prepare the electronwithdrawing CF3-BINAP derivative 101c (Fig. 44).

The functionalisation of binaphthyl-based diphosphinescan be also performed by introduction of different substituentsin practically all positions of the binaphthyl backbone.127,159,160

In this section, we describe the main synthetic approaches for3,30-, 4,40- and 5,50-substituted BINAP derivatives, while thefunctionalisation on positions 6,60 will be discussed inSection 4.

Zhang161 has patented the functionalisation of 3,30-posi-tions through selective 3,30-lithiation162 of (R)- or (S)-BINAPO,

followed by halogenation with bromine or iodine solution oralkylation with methyl iodide. The transformation of 3,30-dihalogenated diphosphine oxide was carried out into a greatvariety of 3,30-aryl derivatives via Suzuki coupling, with subse-quent reduction with HSiCl3, yielding the corresponding 3,30-substituted BINAP 102 and 103. However, no further informa-tion was given regarding yields, purity or applications of thenew BINAP derivatives (Fig. 45).

The preparation of optically pure 4,40-halogenated substi-tuted BINAP derivatives was accomplished through the bromi-nation of BINAPO in the presence of pyridine.163 The resulting4,40-dibromo-BINAPO derivative 104 is a versatile precursor,since the bromine atoms can be directly replaced by multiplefunctional groups. For example,164,165 the reaction of 104 withcopper cyanide allowed the formation of 4,40-dicyano-BINAP105 in a 60% yield (Fig. 46A).

Simultaneously, Lin166 reported different strategies, whichinvolved palladium-catalysed arylation or alkylation of 4,40-dibromo-BINAPO with aryl or alkyl-boronic acids (77–83%yield), or halogen metathesis with copper chloride (99% yield),followed by reduction of the respective phosphine oxides toafford the corresponding diphosphine ligands 106 (Fig. 46B)

Another approach was based on the reduction of 104 to thecorresponding 4,40-dibromo BINAP, which after lithiation with

Fig. 44 Synthesis of non-symmetric BINAP type ligands.

Fig. 45 Synthesis of 3,30 substituted BINAP derivatives.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




n-butyllithium was coupled with different electrophiles, giving107 in 15–74% yields (Fig. 46C).166,167 These ligands have beenapplied in ruthenium-catalysed hydrogenation of ethyl benzoyl-acetate, where the presence of bulky and electron-withdrawingsubstituents in binaphthyl 4,40-positions demonstrated to decreasethe catalyst enantioselectivity when compared to BINAP.

The synthesis of 5,50-substituted BINAP derivatives can beachieved by two different general strategies: (i) BINAPO nitration(Fig. 47A); or (ii) BINAPO halogenation (Fig. 47B). Kumobayashi168

has patented a synthetic procedure which involved treatment ofBINAPO with a typical HNO3–H2SO4 mixture in acetic acid,yielding the desired 5,50-dinitro-BINAPO in 98% yield. The nitrogroup was then easily converted into the corresponding 5,50-diamino-BINAPO, by reduction with tin chloride in acidicmedium, and finally the 5,50-diamino-BINAP 108 was obtainedby common phosphine oxide reduction in 60% yield (Fig. 47A).The nucleophilic amino groups were used in a great varietyof applications such as a linking point for attachment to

Fig. 46 Synthetic methodologies for the preparation of 4,40-disubstituted BINAP derivatives.

Fig. 47 Two routes for synthesis of 5,50-BINAP derivatives.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




polymeric supports169 and to prepare dendritic supramolecularstructures.170

Berthod164 described the preparation of 5,50-dibromo-BINAPOin 80% yield, by treating BINAPO with a 1,2-dichloroethanebromine solution in the presence of iron (Fig. 47B). The 5,50-dihalogenated compound was also shown to be a versatile pre-cursor for the preparation of 5,50-bis(trimethylsilyl)-BINAP 109.171

Several independent research groups described the synthesisof H8-BINAP 110, starting from H8-BINOL, by following nearly thesame synthetic methodologies described for BINAP (Fig. 48).127,154

Noteworthy effects of the partially hydrogenated binaphthyl back-bone were observed; for example, H8-BINAP provided moreenantioselective catalytic systems than BINAP in Ru-catalysedhydrogenation of unsaturated carboxylic acids.154,172

Recently, Pereira, Bayon and Abreu173 described the synthesisof bis-MOP type diphosphines based on two binaphthyl unitslinked by modulated ether spacers. The synthetic methodologyinvolved the coupling of two monoprotected BINOL units with aditosylated alkyl bridge, followed by selective deprotection ofthe benzyl group with BBr3 affording the respective dihydroxy-ether.82,174 The pyridyl counterpart was prepared through aslightly different approach, wherein a diphenylmethoxy groupwas employed as the BINOL mono-protecting group, which waseasily removed with HCl in methanol. This alternative has beenapplied in order to overcome problems related to the use of theBBr3 as deprotection agent, which would concomitantly cleave

the methoxy–pyridyl bond. The diols were then converted intothe corresponding bis-triflates, whose subsequent phosphina-tion afforded the diphosphines 111 and 112 (Fig. 49) in moderateyields. In order to achieve complete conversions, the use ofstoichiometric amounts of NiCl2/dppe in the phosphination ofbis-triflate derivatives was imperative,174 due to the high chelatingability of bis-MOP type ligands towards nickel, generating aNiClx(bis-MOP) inactive complex that blocks the reaction.

Another important class of diphosphines containing abinaphthyl backbone are diphospholes, which unlike BINAPligands, do not present axial chirality due to rapid atropisomerinterconversion at room temperature.175 In this context, Gladiali176

reported the synthesis of chiral bis-dinaphthophospholes throughreaction of 7-phenyldinaphtho[2,1-b;10,20-d]phosphole123 withlithium, followed by coupling with the desired alkyl dihalide orditosylate. After work up, the desired ligands 113–115 wereobtained in moderate yields (47–57%) (Fig. 50).

Furthermore, other examples of phosphine ligands withhighly rigid structure are bis-phosphepine ligands, containingtwo seven-member endocyclic binaphthalene scaffolds presentingaxial chirality. Zhang177,178 reported the synthesis of Binaphane116 and f-Binaphane 117 in 35 and 32% overall yields, respectively(Fig. 51). The synthetic strategy applied for the preparation ofthese ligands involved the derivatisation of enantiopure BINOLwith triflic anhydride in the presence of an excess of pyridine,producing the corresponding BINOL bis-triflate in 99% yield.Triflate substitution by a methyl group was accomplished byreaction with methylmagnesium bromide in the presence of anickel catalyst, followed by bromination of 2,20-dimethyl-1,10-binaphthyl with N-bromosuccinimide (NBS), yielding the corre-sponding dibrominated product. Then, bromine was exchangedby chlorine using lithium chloride and further reacted with thecorresponding diphenylphosphine hydrides in basic media,affording the desired diphosphines 116 and 117. A key elementin this synthesis was the utilization of the less reactive

Fig. 48 Structures of (R) and (S)-H8-BINAP.

Fig. 49 Synthesis of bis-MOP type diphosphine ligands.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




dichlorinated compound, to suppress the intermolecular reactionwith phosphine anions that usually occurs with the more reactivedibrominated adduct.

Other bis-phosphepine ligands were prepared by two alter-native synthetic routes. Moberg179 reported the synthesis of(R,R)-118 containing two dinaphthophosphepine units linkedby an ethane spacer, through reaction of bis(bromomethyl)-1,10-binaphthyl with ammonium hypophosphite as the phos-phorus source in the presence of N,N-diisopropylethylamineand trimethylchlorosilane, followed by reduction with phenyl-silane (PhSiH3). The stability of the phosphorus(III) inter-mediate was increased by protection with BH3 and then reactedwith diethyl vinylphosphonate, followed by the addition ofanother bis(bromomethyl)-1,10-binaphthyl unit, producing

dinaphthophosphepine 118 in 5% overall yield (Fig. 52,route A).

In the same year, Zhang120 reported a different strategy, whichallowed the preparation of the same ligand 118, as well as the 3,30-phenyl substituted bis-phosphepine analogue 119. This syntheticmethodology started with the lithiation of 2,20-dimethyl-1,10-binaphthyl or its analogous 3,30-diphenyl derivative with n-BuLi,followed by reaction with 1,2-bis(dichlorophosphine)ethane pro-ducing the desired bis-phosphepines 118 and 119 with an overallyield of 33 and 28% respectively (Fig. 52, route B).

The same author180 reported the first example of a chiral bis-dinaphthophosphepine ligand (R,R)-120 with stereogenic P andC centres. The employed synthetic methodology consisted ofdouble metallation of enantiopure (R)-2,20-dimethyl-1,10-binaphthyl

Fig. 50 Synthesis of bis-dinaphthophosphole ligands.

Fig. 51 Synthesis of binaphane and f-binaphane ligands.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




with n-BuLi/TMEDA, followed by reaction with tert-butyl-dichlorophosphine and sulfur. Coupling of the two units wasaccomplished via the lithiated intermediate, in the presence ofcopper(II)chloride in basic media, followed by reduction with aperchlorinated silane derivative, affording diphosphepine 120in a modest 25% yield, along with recovery of starting material(Fig. 53).

4. Modified binaphthyl phosphorus ligandsfor alternative reaction media

The high cost of organophosphorus transition metal complexesassociated with the difficulties in catalyst recycling are the mainreasons for their limited spread at an industrial level. Thus, inthe last few decades, multiple attempts have been made in bothacademia and industry to merge the advantageous features ofhomogeneous and heterogeneous catalysis.181–190 In addition,the worldwide demand for sustainable chemistry, particularlyfor environmentally benign solvents in chemical reactions, hasencouraged the development of suitable catalysts for application inalternative reaction media.191,192 Hence, due to the specificity ofeach alternative reaction medium, it became imperative to promotethe appropriate structural modifications on the phosphorus ligandsin order to enhance the catalysts solubility in fluorous solvents,supercritical CO2, ionic liquids, or aqueous medium (Fig. 54).182

In this context, the binaphthyl compounds represent privi-leged precursors, since their rich reactivity, inherent to aromaticcompounds, has made possible to promote several peripheralmodifications, for efficient use in such reaction media.

4.1. Fluorinated derivatives

The concept of fluorous biphasic catalysis (FBC), first introducedby Horvath and Rabai193 in the 1990s, and the application ofsupercritical fluids (SCFs) as co-solvents,194 led to the develop-ment of a new synthetic research area to promote the function-alisation of transition metal ligands with highly fluorinatedchains.195–197 The design of suitable ligands having a highpercentage of fluorine atoms in order to allow their solubilityin FBCs and SCFs is often based on two main features: (i)fluorinated chains directly attached to organic core of theligand;198,199 (ii) spacers between the fluorinated chains andthe organic core of the ligand, to shield phosphorus from thefluorine electron-withdrawing effect.200,201

Regarding the synthesis of fluorinated binaphthyl deriva-tives, Stuart and Xiao described the first synthesis of (R)-BINAPligands bearing fluorinated substituents.202,203 First, the authorspromoted the quantitative bromination of (R)- or (S)-BINOL onthe 6- and 60-positions, using Cram’s method.204 Then, twodifferent routes were developed to promote the synthesis offluoroalkylated binaphthyl phosphines. One synthetic approachinvolved the direct attachment of C6F13-groups to the binaphthylbackbone via a copper-mediated cross-coupling between theperfluoroalkyl iodide and the acetoxy-protected 6,60-dibromo-binaphthyl derivative (Fig. 55A).205,206 In the other approach,the introduction of additional ethyl spacer groups was performedusing a coupling reaction between the benzyloxy-protectedbinaphthyl 6,60-dibromide and the olefin CH2QCHC6F13, catalysedby Herrmann’s palladacycle catalyst.207 Reduction of the doublebond was carried out concomitantly with benzyloxy deprotection

Fig. 52 Synthesis of bis-dinaphthophosphepine ligands.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




using Pd/C as the catalyst (Fig. 55B).203 Both strategies werefollowed by the well-known procedure for the preparation of BINAPphosphines, which basically consisted of the transformationof 6,60-fluoroalkyl-substituted (R)-BINOL derivatives into thecorresponding bis-triflates and subsequent NiCl2(dppe)-catalysedphosphination, yielding 121 and 122 in 43% and 73% overallyields, respectively.

Later, Bannwarth208,209 prepared (S)-6,60-substituted per-fluorinated bis-trialkylsilyl BINAP derivatives, via lithiation ofbenzyloxymethyl (BOM) protected dibromo-binaphthyl deriva-tive followed by coupling with the trialkylsilyl bromide(Fig. 55C). The phosphination step was also carried out usingdiphenylphosphine hydride and NiCl2(dppe) as catalyst. Thedifficulties associated with purification/isolation of 123 wereovercome by isolation through recrystallisation of the corre-sponding diphosphine oxide, formed by oxidation of the diphos-phine with hydrogen peroxide, followed by reduction withtrichlorosilane in 53% yield. Considering that fluorine contentis a crucial aspect for ligand’s application in FBC, it should benoted that ligand 123, which possesses significantly higherfluorine content than ligands 121 and 122, was demonstratedto be the most suitable for use in fluorinated solvents.

More recently, Altinel,210 has described the synthesis of 6,60-diperfluoroalkyl BINAP type diphosphines. The phosphinationstep was performed using diphenyldiphosphine hydride deri-vatives, producing fluorinated diphosphines, having fluorinecontent at the binaphthyl core (124a) or at both the binaphthylcore and phosphorus substituents (124b) (Fig. 56). The fluorinateddiphosphine ligands 124 have been evaluated in rhodium-catalysed hydrogenation of styrene using methanol and super-critical carbon dioxide (scCO2) as solvents. It should be notedthat both catalytic systems gave 100% conversion in metha-nol; however, when a methanol–scCO2 mixture was used assolvent, Rh/124b gave significantly higher activity (96.4%) thanRh/124a.

Sinou reported the synthesis of perfluorinated MOP analo-gues211,212 by reaction of 6,60-fluoroalkyl substituted (R)-BINOLbis-triflate with one equivalent of diphenylphosphonic acid, inthe presence of catalytic amounts of Pd(OAc)2. After basichydrolysis of the remaining triflate group another fluorouschain was introduced by reaction with 1H,1H-perfluorooctyl-1-ol perfluorobutanesulfonate followed by reduction, affordingenantiopure 125 in 40% overall yield (Fig. 57A). In a similar way,the same author has prepared the 6,60-fluorinated trialkylsilylMOP 126, through introduction of a 2-methoxy group by nucleo-philic substitution with iodomethane in 43% overall yield(Fig. 57B).

In a different approach, the same group described thepreparation of a fluorinated chiral phosphine, in which thefluorine-containing substituents are attached to the phosphinebenzene rings213 and at the binaphthyl 20-position. In thismethodology, (R)-BINOL bis-triflate was reacted with bis(4-methoxyphenyl)phosphonic acid in the presence of equimolaramounts of Pd(OAc)2 and 1,4-bis(diphenylphosphino)butane(dppb) to produce the monophosphinoylated product. Aftermethoxy group deprotection with BBr3 and hydrolysis of theremaining triflate with NaOH, the introduction of fluorinatedalkyl chains was performed by nucleophilic substitution reac-tion of the free hydroxyl groups with a fluoroalkyliodide. Finally,

Fig. 53 Synthesis of P,C stereogenic bis-phosphepine ligands.

Fig. 54 Typical alternative solvents for biphasic reactions.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




reduction with trichlorosilane afforded the desired enantiopurephosphine (R)-127 in 45% overall yield (Fig. 58). Fluorinatedligands 125–127 have been tested in palladium-catalysed asym-metric allylic substitution of 1,3-diphenyl-2-propenyl acetate,using organic solvents as reaction media, achieving up to 87%ee with the catalytic system Pd/127. The authors referred to thefact that the fluorine content present on these ligands was notenough to allow their use in successful FBC systems, eventhough it was possible to perform their easy separation from

the reaction products through liquid–liquid extraction withperfluorocarbons.

Independently, Gennari21 and Masdeu-Bulto214 groups haveextended the concept of fluorinated phosphorus ligands to theclass of binaphthyl phosphite derivatives. Following the standardprocedures for the synthesis of monophosphite ligands, the couplingof BINOL phosphochloridite with the corresponding fluoro-aryl orfluoro-alkyl alcohols afforded the desired fluorinated phosphites128a–c in 52, 60 and 64% isolated yields, respectively (Fig. 59).

Fig. 55 Synthesis of binaphthyl fluoro-alkylated substituted diphosphines.

Fig. 56 Synthesis of fluorinated diphosphine ligand.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




The rhodium-catalysed asymmetric hydrogenation of acrylicacid derivatives using fluorinated monophosphite ligands 128aand 128b was carried out in different reaction media, such asorganic solvent (dichloromethane), ionic liquid ([BMI][PF6]),supercritical carbon dioxide (scCO2) and [BMI][PF6]/scCO2 mix-ture,214 while ligand 128c was only tested in dichloromethane.21

Moderate activities were obtained by all catalytic systems, whilethe best enantiodiscrimination (up to 80% ee) was achievedwith Rh/128a in [BMI][PF6]. Furthermore, the catalyst could berecycled up to ten times without activity loss, albeit with asignificant decrease in enantioselectivity.

Leitner reported the synthesis of a fluorinated hybrid phosphine–phosphite BINAPHOS derivative 129.215–218 This ligand wasprepared according to an adaptation of the well-known proceduresdescribed by Takaya,219 in which the enantiopure (R)-binaphthylbis(trifluoromethanesulfonate) was monophosphonoylated, bycoupling with a fluorinated diphenylphosphine oxide in thepresence of catalytic amounts of Pd(OAc)2/dppb, followed by

phosphine oxide reduction with HSiCl3 and triflate deprotectionin the presence of triethylamine. Finally, (R)-2-(diphenyl-phosphino)-1,10-binaphthalen-20-triflate was reacted with the(S)-binaphthyl phosphochloridite in triethylamine to give thedesired fluorinated (R,S)-BINAPHOS 129, in 60% yield. (Fig. 60A).218

Ojima described another approach for the synthesis ofstructurally different fluorinated BINAPHOS derivatives, inwhich the fluorine content is present in the phosphite frag-ment.220 Starting from tert-butyldimethylsilyl (TBS) protected(R)- or (S)-6,6 0-dibromobinaphthyl derivative, the preparation of6,60-diallyl substituted BINOL was performed via coupling withan allylstannane. Then, palladium-catalysed addition of per-fluoroalkyl iodide, followed by lithium–aluminium hydridedehalogenation and subsequent TBS deprotection with tetra-butylammonium fluoride (TBAF), afforded the 6,60-bis(fluorinatedalkyl) BINOL derivative. Finally, this compound was convertedinto the corresponding phosphochloridite and then coupled with(S)- or (R)-2-hydroxy-20-diphenylphosphino-1,10-binaphthyl, giving

Fig. 57 Synthesis of fluorinated MOP analogues.

Fig. 58 Synthesis of fluorinated aryl-MOP ligands.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




130, in 65% yield (Fig. 61B).102 The rhodium complexes of 129 and130 were evaluated in the rhodium-catalysed asymmetric hydro-formylation of vinylarenes, in benzene or in biphasic scCO2/benzene reaction media. Using Rh/130 as a biphasic catalyst,comparable or ever higher regio- and enantioselectivities wereobtained in the asymmetric hydroformylation of styrene, whencompared to those obtained by the conventional single-phaseRh/BINAPHOS system.220

4.2. Hydrophilic derivatives

The high price and rather complicated synthesis of organo-fluorinated ligands led to the search for less expensive alter-native reaction media, like water or ionic liquids, for carrying

Fig. 59 Synthesis of fluorinated monophosphite ligands.

Fig. 60 Synthesis of phosphine–phosphite BINAP fluorinated derivatives.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




out two-phase catalysed organic reactions. For that purpose, thefunctionalisation of transition metal ligands with polar and/orhydrophilic substituents became a key research area. Aqueousbiphasic catalysis has attracted great attention as can be seenby a number of industrial applications, both in fine and bulkchemical industry.187,221–224 An early success of aqueous biphasicsystems is the Ruhrchemie/Rhone-Poulenc hydroformylationprocess, for the production of butanal, using the water solublesulfonated triphenylphosphine as rhodium(I) ligand.187 On theother hand, ionic liquids have been considered potential candi-dates to replace organic solvents due to their very low vapourpressure and their good thermal stability.225,226 The ground-breaking studies of Knifton227 based on metal carbonyl speciesof ruthenium and cobalt-catalysed hydroformylation of internaland terminal alkenes in molten tetrabutylphosphonium bromide,[Bu4P]Br, were one of the first examples of successful homo-geneous transition metal catalysis using ionic liquids as solvents.

It should be noted that the development of catalytic systemsusing water or ionic liquids as alternative solvents requires thepreparation of hydrophilic metal complexes with ligands con-taining polar groups. Thus, induction of hydrophilicity hasbeen achieved by structural ligand modifications with sulfonic,carboxylic, phosphonic and electrostatically charged groups.

Despite the diverse range of possibilities concerning thehydro-solubilisation of phosphines, sulfonation is the mostused strategy. The first water soluble binaphthyl based phos-phine was reported by Davis, in 1993,228,229 by reaction of(R)-BINAP with a solution of sulfur trioxide in sulfuric acid (oleum),at low temperature (10 1C), followed by quenching in ice-waterand careful neutralisation with NaOH, yielding (R)-131 (Fig. 61).Furthermore, using the same synthetic strategy, Hanson pre-pared another sulfonated ligand, starting from the racemicBINAP derivative,148 through reaction of racemic 2,20-bis-(di[p-(3-phenylpropyl)phenyl]phosphino)-1,10-binaphthalene witholeum followed by treatment with NaOH, to give ligand 132 in40% overall yield. The Rh/131 complex has been evaluated inasymmetric hydrogenation of acrylic acid derivatives in water,where enantioselectivities were similar to those achieved withBINAP in non-aqueous solvents.228 Moreover, the catalyst Rh/132has been evaluated in two phase (water:methanol:oct-1-ene)hydroformylation of oct-1-ene and excellent regioselectivity for

the formation of nonanal (97%) was obtained, with no catalystloss into the organic phase.128

The rhodium and ruthenium complexes of sulfonated(R)-BINAP/1-butyl-3-methyl imidazolium [BMI][BF4] 133, were laterprepared by Yuan,230,231 by mixing the sulfonated (R)-BINAP,prepared with a similar strategy as for 131, with ionic liquid[BMI][BF4] (Fig. 62), and evaluated in biphasic catalytic systems([BMI][BF4]:toluene) on asymmetric hydroformylation of vinylacetate and hydrogenation of dimethyl itaconate, achieving, inboth cases, moderate activities and enantioselectivities.

Herrmann described the synthesis of the sodium salts ofwater soluble binaphthyl based diphosphine 135232–234 viasulfonation of racemic NAPHOS diphosphine 134 witholeum,232 at both the binaphthyl backbone and the phosphorusatom. The reaction work-up, which represents the most delicatestage, was carried out by careful quenching of the crudeproduct mixture with degassed ice-water. The strongly acidicsolution was then neutralised with sodium hydroxide. Afterpartial removal of water in vacuum, the resulting suspensionwas cooled and poured into cold methanol to precipitate thesodium sulphate. The filtrate was concentrated to dryness,giving BINAS-Na 135. This compound is still considered oneof the most important ligands for use in industrial aqueousbiphasic catalysis, due to its high activity and selectivity inbiphasic water rhodium-catalysed hydroformylation of propene.Later on, the same group235 extended the same methodology topreparation of chiral BINAS-Na, starting from (S)-NAPHOS 134,yielding (S)-BINAS-Na with 80% yield, without racemisation. TheRh/(S)-135 complexes were applied in aqueous/organic biphasichydroformylation of styrene, achieving lower enantiomericexcesses than those obtained in the conventional single-phasereaction (Fig. 63).

Phosphonic groups have also been demonstrated to besuitable substituents in binaphthyl ligands for biphasic reac-tions in aqueous media. In this context, Kockritz236,237 describedthe preparation of phosphonic BINAP derivatives, through reac-tion of dibromo-binaphthyl diphosphine oxide with diethylphos-phonate. The reduction of the phosphorylated species withphenylsilane to the corresponding diphosphine was followedby hydrolysis of the phosphonate groups with bromotrimethyl-silane, giving the 4,40-diphosphonic acid substituted BINAP

Fig. 62 Sulfonated BINAP-ionic liquid derivative.

Fig. 61 Synthesis of sulfonated BINAP derivatives.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




derivative, which was further transformed in its sodium salt 136in 10% overall yield (Fig. 64). This ligand was evaluated inbiphasic rhodium-catalysed hydroformylation of vinylacetateand styrene and also in asymmetric hydrogenation of dimethylitaconate. The authors observed similar activities and selectivitiesto the ones obtained in the homogeneous systems. Moreover,this phosphorylated BINAP ligand was able to be employed inaqueous biphasic systems, offering the advantage of simplecatalyst recycling.

Furthermore, Lemaire described several reports on thesynthesis of BINAP diphosphines bearing ammonium quater-nised substituents in various positions of the binaphthyl skeleton,in order to enhance their solubilisation in water.160,164,238–240 Ingeneral, the cyano-BINAP derivatives were reduced with LiAlH4

to give the corresponding amino-BINAP compounds. Simpleaqueous HBr addition transformed these ligands into the desiredbromide ammonium quaternised water soluble salts 137–140(Fig. 65). The ruthenium complexes of these ligands were testedin homogeneous and water/organic solvent biphasic asymmetrichydrogenation of b-ketoesters leading to 100% conversions andenantiomeric excesses up to 98% in water. Catalysts could berecycled several times by extraction of the product with pentanewith practically no loss of activity and just a slight decrease in theenantioselectivity.160,239,240

Reetz and Gavrilov241 described the synthesis of a new classof P-monodentate phosphite ligands bearing ionic liquid frag-ments (Fig. 66) by reaction of (S)-BINOL phosphochloridite withan equimolar solution of imidazolium based ionic liquid andtriethylamine, in dichloromethane, giving 141 in 40% isolatedyield.

The Rh/141 complexes were tested as catalysts in the asym-metric hydrogenation of acrylates, while palladium complexes

of 141 were used in asymmetric allylic substitution reactions, inorganic solvents, in which the authors observed excellentactivities and enantioselectivities (up to 99% ee). Althoughthe reutilisation of the catalyst was not described, the excellentcatalytic performance of these metal complexes makes themattractive candidates for the development of reusable catalystsinvolving biphasic systems (organic solvent/ionic liquids).

5. Conclusion

The synthetic availability and thermal stability of axially chiralbinaphthyl-based molecules, together with their easy modula-tion, inherent to aromatic reactivity, has turned BINOL into aremarkable building block for the synthesis of a wide variety ofenantiomerically pure phosphorus ligands. The improvementof efficient chemical synthetic methods for preparation ofchiral binaphthyl-based phosphite and phosphine ligands hasbeen accomplished throughout several standardised approaches,which may involve either the employment of enantiopure orracemic BINOL as starting materials. While the modulation ofphosphite ligands is generally accomplished by modification ofthe BINOL backbone prior to the addition of phosphorus moiety,in the case of phosphines the insertion of substituents is oftenperformed subsequent to the phosphorus moiety introductionstep. Additional chirality from other chiral sources allows theformation of diastereomeric phosphorus compounds, which areoften separated by fractional crystallisation or chromatographicmethods. Moreover, the binaphthyl core fine tuning with suitablefluorinated chains or hydrophilic substituents has been guidingthe scientific community towards broad opportunities for thepreparation of highly active and selective catalytic systems withthe possibility of easy recovery, recycling and reuse.

Fig. 63 Synthesis of water soluble sulfonated binaphthyl based diphosphine BINAS-Na.

Fig. 64 Synthesis of water soluble phosphonic acid BINAP derivative.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




In conclusion, huge developments have been carried outconcerning the synthesis of binaphthyl-based phosphite andphosphine ligands, used as versatile chiral auxiliaries in asym-metric catalysis. Further systematic modulation of steric and/orelectronic features, either at the binaphthyl backbone or at thephosphorus coordination sphere, are expected to lead to acontinuing research on detailed exploration of diverse asym-metric catalytic reactions, aiming to improve aspects related tocatalyst activity, selectivity and reutilisation.

Acknowledgements

The authors are grateful to Fundaçao para a Ciencia e aTecnologia (FCT) (COMPETE–Programa Operacional Factoresde Competitividade), QREN/FEDER for funding through ProjectPTDC/QUI-QUI/112913/2009. M. J. F. Calvete thanks FCT/QREN/FEDER for Program Ciencia 2008.

References

1 J. M. Brunel, Chem. Rev., 2007, 105, 857.2 1,10-Binaphthyl-Based Chiral Materials: Our Journey, ed.

L. Pu, Imperial College Press, London, 2010.3 D. J. Cram, R. C. Helgeson, S. C. Peacock, L. J. Kaplan,

L. A. Domeier, P. Moreau, K. Koga, J. M. Mayer, Y. Chao,M. G. Siegel, D. H. Hoffman and G. D. Y. Sogah, J. Org.Chem., 1978, 43, 1930.

4 H. Guo and K. Ding, Tetrahedron Lett., 2000, 41, 10061.5 D.-W. Wang, S.-M. Lu and Y.-G. Zhou, Tetrahedron Lett.,

2009, 50, 1282.

6 A. Korostylev, V. I. Tararov, C. Fischer, A. Monsees andA. Borner, J. Org. Chem., 2004, 69, 3220.

7 Y. Chen, S. Yekta and A. K. Yudin, Chem. Rev., 2003, 103, 3155.8 New Frontiers in Asymmetric Catalysis, ed. K. Mikami and

M. Lautens, Wiley & Sons, New Jersey, 2007.9 Phosphorus Ligands in Asymmetric Catalysis, ed. A. Borner,

Wiley & Sons, Weinheim, 2008.10 Phosphorus(III) Ligands in Homogeneous Catalysis. Design

and Synthesis, ed. P. C. J. Kamer and P. W. N. M. vanLeeuwen, Wiley & Sons, Chichester, 2012.

11 G. Erre, S. Enthaler, K. Junge, S. Gladiali and M. Beller,Coord. Chem. Rev., 2008, 252, 471.

12 L. Eberhardt, D. Armspach, J. Harrowfield and D. Matt,Chem. Soc. Rev., 2008, 37, 839.

13 P. W. N. M. van Leeuwen, P. C. J. Kamer, C. Claver,O. Pamies and M. Dieguez, Chem. Rev., 2011, 111, 2077.

14 T. Jerphagnon, J.-L. Renaud and C. Bruneau, Tetrahedron:Asymmetry, 2004, 15, 2101.

15 K. N. Gavrilov, S. E. Lyubimov, S. V. Zheglov, E. B. Benetskyand V. A. Davankov, J. Mol. Catal. A: Chem., 2005, 231, 255.

16 M. T. Reetz and G. Mehler, Angew. Chem., Int. Ed., 2000,39, 3889.

17 M. T. Reetz, G. Mehler, A. Meiswinkel and T. Sell, TetrahedronLett., 2002, 43, 7941.

18 M. T. Reetz, T. Sell, A. Meiswinkel and G. Mehler, Angew.Chem., Int. Ed., 2003, 42, 790.

19 S. Matsunaga, J. Das, J. Roels, E. M. Vogl, N. Yamamoto,T. Iida, K. Yamaguchi and M. Shibasaki, J. Am. Chem. Soc.,2000, 122, 2252.

20 M. T. Reetz, J.-A. Ma and R. Goddard, Angew. Chem., 2005,117, 416.

Fig. 65 Synthesis of amino-BINAP bromine salts.

Fig. 66 Synthesis of chiral binaphthyl-based ionic imidazolium–phosphite ligands.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




21 B. Lynikaite, J. Cvengros, U. Piarulli and C. Gennari,Tetrahedron Lett., 2008, 49, 755.

22 W. Chen and J. Xiao, Tetrahedron Lett., 2001, 42, 2897.23 A. Iuliano, P. Scafato and R. Torchia, Tetrahedron: Asymmetry,

2004, 15, 2533.24 A. Iuliano, D. Losi and S. Facchetti, J. Org. Chem., 2007,

72, 8472.25 M. T. Reetz, L. J. Goossen, A. Meiswinkel, J. Paetzold and

J. F. Jensen, Org. Lett., 2003, 5, 3099.26 H. Huang, Z. Zheng, H. Luo, C. Bai, X. Hu and H. Chen,

Org. Lett., 2003, 5, 4137.27 H. Huang, Z. Zheng, H. Luo, C. Bai, X. Hu and H. Chen,

J. Org. Chem., 2004, 69, 2355.28 T. Jerphagnon, J. L. Renaud, P. Demonchaux, A. Ferreira

and C. Bruneau, Adv. Synth. Catal., 2004, 346, 33.29 H. Huang, X. Liu, S. Chen, H. Chen and Z. Zheng, Tetrahedron:

Asymmetry, 2004, 15, 2011.30 H. Huang, X. Liu, H. Chen and Z. Zheng, Tetrahedron:

Asymmetry, 2005, 16, 693.31 S. E. Lyubimov, I. V. Kuchurov, A. A. Tyutyunov, P. V.

Petrovskii, V. N. Kalinin, S. G. Zlotin, V. A. Davankov andE. Hey-Hawkins, Catal. Commun., 2010, 11, 419.

32 S. E. Lyubimov, A. A. Tyutyunov, V. N. Kalinin, E. E. Said-Galiev, A. R. Khokhlov, P. V. Petrovskii and V. A. Davankov,Tetrahedron Lett., 2007, 48, 8217.

33 S. E. Lyubimov, V. N. Kalinin, A. A. Tyutyunov, V. A.Olshevskaya, Y. V. Dutikova, C. S. Cheong, P. V. Petrovskii,A. S. Safronov and V. A. Davankov, Chirality, 2009, 21, 2.

34 W. Chen, S. M. Roberts and J. Whittall, Tetrahedron Lett.,2006, 47, 4263.

35 X.-P. Hu, J.-D. Huang, Q.-H. Zeng and Z. Zheng, Chem.Commun., 2006, 293.

36 K. N. Gavrilov, S. E. Lyubimov, P. V. Petrovskii, S. V.Zheglov, A. S. Safronov, R. S. Skazov and V. A. Davankov,Tetrahedron, 2005, 61, 10514.

37 K. N. Gavrilov, S. E. Lyubimov, S. V. Zheglov, E. B.Benetsky, P. V. Petrovskii, E. A. Rastorguev, T. B.Grishina and V. A. Davankov, Adv. Synth. Catal., 2007,349, 1085.

38 K. N. Gavrilov, S. V. Zheglov, M. N. Gavrilova, I. M. Novikov,M. G. Maksimova, N. N. Groshkin, E. A. Rastorguev andV. A. Davankov, Tetrahedron, 2012, 68, 1581.

39 W.-J. Shi, J.-H. Xie and Q.-L. Zhou, Tetrahedron: Asymmetry,2005, 16, 705.

40 W. Bo, K. F. Yee, W. Lailai, X. Lijin, Z. Qinglu andX. Aiping, Chin. J. Catal., 2011, 32, 80.

41 C. Moberg, Angew. Chem., Int. Ed., 1998, 37, 248.42 S. E. Gibson and M. P. Castaldi, Chem. Commun., 2006,

3045.43 M. T. Reetz, H. Guo, J.-A. Ma, R. Goddard and R. J. Mynott,

J. Am. Chem. Soc., 2009, 131, 4136.44 R. M. B. Carrilho, A. R. Abreu, G. Petocz, J. C. Bayon,

M. J. S. M. Moreno, L. Kollar and M. M. Pereira, Chem.Lett., 2009, 844.

45 R. M. B. Carrilho, A. C. B. Neves, M. A. O. Lourenço, A. R.Abreu, M. T. S. Rosado, P. E. Abreu, M. E. S. Eusebio,

L. Kollar, J. C. Bayon and M. M. Pereira, J. Organomet.Chem., 2012, 698, 28.

46 O. Mitsunobu, Synthesis, 1981, 1.47 R. M. B. Carrilho, M. M. Pereira, A. Takacs and L. Kollar,

Tetrahedron, 2012, 68, 204.48 M. T. Reetz, A. Meiswinkel, G. Mehler, K. Angermund,

M. Graf, W. Thiel, R. Mynott and D. G. Blackmond, J. Am.Chem. Soc., 2005, 127, 10305.

49 M. J. Baker and P. G. Pringle, J. Chem. Soc., Chem. Commun.,1991, 1292.

50 M. Yan and A. S. C. Chan, Tetrahedron Lett., 1999, 40, 6645.51 M. Yan, L.-W. Yang, K.-Y. Wong and A. S. C. Chan, Chem.

Commun., 1999, 11.52 S. Cserepi-Szucs, G. Huttner, L. Zsolnai, A. Szolo +osy,

C. Hegedus and J. Bakos, Inorg. Chim. Acta, 1999,296, 222.

53 M. Yan, Z.-Y. Zhou and A. S. C. Chan, Chem. Commun.,2000, 115.

54 M. Yan, Q.-Y. Xu and A. S. C. Chan, Tetrahedron: Asymmetry,2000, 11, 845.

55 G. J. H. Buisman, L. A. van der Veen, A. Klootwijk, W. G. J.de Lange, P. C. J. Kamer, P. W. N. M. van Leeuwen andD. Vogt, Organometallics, 1997, 16, 2929.

56 S. Cserepi-Szucs and J. Bakos, Chem. Commun., 1997, 635.57 J. Bakos, S. Cserepi-Szucs, A. Gomory, C. Hegedus,

L. Marko and A. Szollosy, Can. J. Chem., 2001, 79, 725.58 Y. Jiang, S. Xue, K. Yu, Z. Li, J. Deng, A. Mi and A. S. C.

Chan, J. Organomet. Chem., 1999, 586, 159.59 M. T. Reetz and T. Neugebauer, Angew. Chem., Int. Ed.,

1999, 38, 179.60 O. Pamies, G. Net, A. Ruiz and C. Claver, Eur. J. Inorg.

Chem., 2000, 1287.61 M. Dieguez, A. Ruiz and C. Claver, J. Org. Chem., 2002,

67, 3796.62 M. Dieguez, A. Ruiz and C. Claver, Dalton Trans., 2003, 2957.63 E. Guiu, B. Munoz, S. Castillon and C. Claver, Adv. Synth.

Catal., 2003, 345, 169.64 A. Gual, M. R. Axet, K. Philippot, B. Chaudret, A. Denicourt-

Nowicki, A. Roucoux, S. Castillon and C. Claver, Chem.Commun., 2008, 2759.

65 M. R. Axet, J. Benet-Buchholz, C. Claver and S. Castillon,Adv. Synth. Catal., 2007, 349, 1983.

66 A. Gual, C. Godard, C. Claver and S. Castillon, Eur. J. Org.Chem., 2009, 1191.

67 A. Gual, C. Godard, S. Castillon and C. Claver, Adv. Synth.Catal., 2010, 352, 463.

68 Q.-L. Zhao, M. K. Tse, L. L. Wang, A. P. Xing and X. Jiang,Tetrahedron: Asymmetry, 2010, 21, 2788.

69 L.-L. Wang, Y. M. Li, C. W. Yip, L. Q. Qiu, Z. Y. Zhou andA. S. C. Chan, Adv. Synth. Catal., 2004, 346, 947.

70 X. Jia, L. Wang, A. S. C. Chan and Y. Li, Chin. J. Catal., 2007,28, 492.

71 Q. L. Zhao and L. L. Wang, Tetrahedron: Asymmetry, 2011,22, 1885.

72 L.-L. Wang, R.-W. Guo, Y.-M. Li and A. S. C. Chan, Tetrahedron:Asymmetry, 2005, 16, 3198.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




73 Q.-L. Zhao, L.-L. Wang, F. Y. Kwong and A. S. C. Chan,Tetrahedron: Asymmetry, 2007, 18, 1899.

74 M. T. Reetz, G. Mehler and O. Bondarev, Chem. Commun.,2006, 2292.

75 S. Cserepi-Szucs, G. Huttner, L. Zsolnai and J. Bakos,J. Organomet. Chem., 1999, 586, 70.

76 J. Wilting, M. Janssen, C. Muller, M. Lutz, A. L. Spek andD. Vogt, Adv. Synth. Catal., 2007, 349, 350.

77 S. E. Lyubimov, A. A. Tyutyunov, P. A. Vologzhanin andA. S. Safranov, J. Organomet. Chem., 2008, 693, 3321.

78 S. E. Lyubimov, R. P. Zhuravskii, V. I. Rozenberg, A. S.Safronov, P. V. Petrovskii and V. A. Davankov, Russ. Chem.Bull., 2008, 57, 137.

79 Z. Freixa, E. Martin, S. Gladiali and J. C. Bayon, Appl.Organomet. Chem., 2000, 14, 57.

80 Z. Freixa and J. C. Bayon, J. Chem. Soc., Dalton Trans., 2001,2067.

81 A. F. R. O. Peixoto, Desenvolvimento de novos catalisadoresde metais de transiçao – Catalise de reacçoes de carbonilaçaoconducentes a obtençao de produtos de valor acrescentado,PhD thesis, University of Coimbra, 2010, http://hdl.handle.net/10316/17793.

82 A. R. Abreu, M. M. Pereira and J. C. Bayon, Tetrahedron,2010, 66, 743.

83 A. R. Abreu, Sıntese de hidroxieteres quirais e de algunsderivados de fosforo: novos catalisadores para alquilaçaoassimetrica de aldeıdos e carbonilaçao de olefinas, PhDthesis, University of Coimbra, 2010, http://hdl.handle.net/10316/14553.

84 G. Ionescu, J. I. van der Vlugt, H. C. L. Abbenhuis andD. Vogt, Tetrahedron: Asymmetry, 2005, 16, 3970.

85 D. Semeril, D. Matt and L. Toupet, Chem.–Eur. J., 2008,14, 7144.

86 L. Monnereau, D. Semeril, D. Matt and L. Toupet, Adv.Synth. Catal., 2009, 351, 1629.

87 Comprehensive Asymmetric Catalysis, ed. E. N. Jacobsen,A. Pfaltz and H. Yamamoto, Springer, New York, 1999.

88 T. Hayashi, J. W. Han, A. Takeda, J. Tang, K. Nohmi,K. Mukaide, H. Tsuji and Y. Uozumi, Adv. Synth. Catal.,2001, 343, 279.

89 T. Hayashi, H. Iwamura, M. Naito, Y. Matsumoto,Y. Uozumi, M. Miki and K. Yanagi, J. Am. Chem. Soc.,1994, 116, 775.

90 M. Kawatsura, Y. Uozumi, M. Ogasawara and T. Hayashi,Tetrahedron, 2000, 56, 2247.

91 K. Ito, S. Eno, B. Saiton and T. Katsuki, Tetrahedron Lett.,2005, 46, 3981.

92 T. Hayashi, Acc. Chem. Res., 2000, 33, 354.93 J.-X. Chen, J. F. Daeuble and J. M. Stryker, Tetrahedron,

2000, 56, 2789.94 Y. Uozumi, N. Suzuki, A. Ogiwara and T. Hayashi, Tetra-

hedron, 1994, 50, 4293.95 Q. Zeng, H. Zeng and Z. Yang, Synth. Commun., 2011,

41, 3556.96 T. Shimada, Y.-H. Cho and T. Hayashi, J. Am. Chem. Soc.,

2002, 124, 13396.

97 Y.-H. Cho, A. Kina, T. Shimada and T. Hayashi, J. Org.Chem., 2004, 69, 3811.

98 K. Tamao, K. Sumitani and M. Kumada, J. Am. Chem. Soc.,1972, 94, 4374.

99 M. Meskova and M. Putala, Tetrahedron Lett., 2011,52, 5379.

100 A. O. King, N. Okukado and E.-I. Negishi, J. Chem. Soc.,Chem. Commun., 1977, 19, 683.

101 B. M. Trost, D. L. Van Vranken and C. Bingel, J. Am. Chem.Soc., 1992, 114, 9327.

102 Y. Uozumi, A. Tanahashi, S. Y. Lee and T. Hayashi, J. Org.Chem., 1993, 58, 1945.

103 Y. Kawashima, K. Okano, K. Nozaki and T. Hiyama, Bull.Chem. Soc. Jpn., 2004, 77, 347.

104 T. Hamada, A. Chieff, J. Åhman and S. L. Buchwald, J. Am.Chem. Soc., 2002, 124, 1261.

105 A. Ficks, I. Martinez-Botella, B. Stewart, R. W. Harrington,W. Clegg and L. J. Higham, Chem. Commun., 2011,47, 87274.

106 X. Xie, T. Y. Zhang and Z. Zhang, J. Org. Chem., 2006,71, 6522.

107 B. Saha and T. V. RajanBabu, J. Org. Chem., 2007, 72, 2357.108 S. Gladiali, D. Antonio and F. Davide, Tetrahedron:

Asymmetry, 1994, 5, 1143.109 T. Hoshi, T. Hayakawa, T. Suzuki and H. Hagiwara, J. Org.

Chem., 2005, 70, 9085.110 T. Hoshi, K. Sasaki, S. Sato, Y. Ishii, T. Suzuki and

H. Hagiwara, Org. Lett., 2011, 13, 932.111 K. V. L. Crepy and T. Imamoto, Adv. Synth. Catal., 2003,

345, 79.112 K. B. Lipkowitz, C. A. D’Hue, T. Sakamoto and J. N. Stack,

J. Am. Chem. Soc., 2002, 124, 14255.113 N. J. Kerrigan, E. C. Dunne, D. Cunningham, P. McArdle,

K. Gilligan and D. G. Gilheany, Tetrahedron Lett., 2003,44, 8461.

114 M.-C. Duclos, Y. Singjunla, C. Petit, A. Favre-Reguillon,E. Jeanneau, F. Popowycz, E. Metay and M. Lemaire,Tetrahedron Lett., 2012, 53, 5984.

115 L. J. Higham, E. F. Clarke, H. Muller-Bunz and D. G.Gilheany, J. Organomet. Chem., 2005, 690, 211.

116 E. F. Clarke, E. Rafter, H. Muller-Bunz, L. J. Higham andD. G. Gilheany, J. Organomet. Chem., 2011, 696, 3608.

117 E. F. Clarke, E. Rafter, H. Muller-Bunz, L. J. Higham andD. G. Gilheany, J. Organomet. Chem., 2011, 696, 3608.

118 T. Hamada and S. L. Buchwald, Org. Lett., 2002, 4, 999.119 K. Junge, G. Oehme, A. Monsees, T. Riermeier,

U. Dingerdissen and M. Beller, Tetrahedron Lett., 2002,43, 4977.

120 Y. Chi and X. Zhang, Tetrahedron Lett., 2002, 43, 4849.121 S. Gladiali, A. Dore, D. Fabbri, O. De Lucchi and

M. Manassero, Tetrahedron: Asymmetry, 1994, 5, 511.122 K. Junge, B. Hagemann, S. Enthaler, A. Spannenberg,

M. Michalik, G. Oehme, A. Monsees, T. Riermeier andM. Beller, Tetrahedron: Asymmetry, 2004, 15, 2621.

123 A. Dore, D. Fabbri, S. Gladiali and O. De Lucchi, Chem.Commun., 1993, 1124.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




124 A. A. Watson, A. C. Willis and S. B. Wild, J. Organomet.Chem., 1993, 445, 71.

125 P. Kasak, V. B. Arion and M. Widhalm, Tetrahedron:Asymmetry, 2006, 17, 3084.

126 Z. Cao, Y. Liu, Z. Liu, X. Feng, M. Zhuang and H. Du, Org.Lett., 2011, 13, 2164.

127 M. Berthod, G. Mignani, G. Woodward and M. Lemaire,Chem. Rev., 2005, 105, 1801.

128 R. Noyori, Angew. Chem., Int. Ed., 2008, 41.129 K. Tani, T. Yamagata, S. Otsuka, S. Akutagawa,

H. Kumobayashi, T. Taketomi, H. Takaya, A. Miyashitaand R. Noyori, J. Chem. Soc., Chem. Commun., 1982, 600.

130 K. Tani, T. Yamagata, S. Akutagawa, H. Kumobayashi,T. Taketomi, H. Takaya, A. Miyashita, R. Noyori andS. Otsuka, J. Am. Chem. Soc., 1984, 106, 5208.

131 A. Miyashita, A. Yasuda, H. Takaya, K. Toriumi, T. Ito,T. Souchi and R. Noyori, J. Am. Chem. Soc., 1980, 102, 7932.

132 A. Miyashita, H. Takaya, T. Souchi and R. Noyori, Tetra-hedron, 1984, 40, 1245.

133 K. J. Brown, M. S. Berry, K. C. Waterman, D. Lingenfelt andJ. R. Murdoch, J. Am. Chem. Soc., 1984, 106, 4717.

134 T. Ohta, H. Takaya and R. Noyori, Inorg. Chem., 1988,27, 566.

135 H. Takaya, T. Ohta, S. Inoue, M. Tokunaga, M. Kitamuraand R. Noyori, Org. Synth., 1995, 72, 74.

136 D. J. Ager and S. A. Laneman, Tetrahedron: Asymmetry,1997, 20, 3327.

137 R. Noyori and T. Ohkuma, Angew. Chem., Int. Ed., 2001,40, 40.

138 T. Ohkuma, M. Koizumi, K. Muniz, G. Hilt, C. Kabuto andR. Noyori, J. Am. Chem. Soc., 2002, 124, 6508.

139 R. Noyori and T. Ohkuma, Pure Appl. Chem., 1999, 71, 1493.140 H. Takaya, K. Mashima, K. Koyano, M. Yagi, H. Kumobayashi,

T. Taketomi, S. Akutagawa and R. Noyori, J. Org. Chem., 1986,51, 629.

141 D. Cai, J. F. Payack and T. R. Verhoeven, US. Pat., 5399771, 1995.142 D. Cai, J. F. Payack, D. R. Bender, D. L. Hughes, T. R.

Verhoeven and P. J. Reider, J. Org. Chem., 1994, 59, 7180.143 S. A. Laneman, D. J. Agger and A. Eisenstadt, US. Pat.,

5902904, 1999.144 D. J. Ager, M. B. East, A. Eisenstadt and S. A. Laneman,

Chem. Commun., 1997, 2359.145 H. Takaya, T. Ohta, N. Sayo, H. Kumobayasi, S. Akutagawa,

S. Inoue, I. Kasahara and R. Noyori, J. Am. Chem. Soc., 1987,109, 1596.

146 O. M. Demchuk, D. Arlt, R. Jasinski and K. M.Pietrusiewicz, J. Phys. Org. Chem., 2012, 25, 1006.

147 M. Alame, M. Jahjah, S. Pellet-Rostaing, M. Lemaire,V. Meille and C. de Bellefon, J. Mol. Catal. A: Chem.,2007, 271, 18.

148 H. Ding, J. Kang, B. E. Hanson and C. W. Kohlpaintner,J. Mol. Catal. A: Chem., 1997, 124, 21.

149 H. Ding, E. B. Hanson and W. C. Kohlpaintner, EP. Pat.,0898573, 1997.

150 T. Oh, N. Sayo, T. Yokozawa, A. Yoshida and X. Zhang,EP. Pat., 0771812, 1997.

151 M. Yamano, M. Goto and M. Yamada, US. Pat., 7541498,2009.

152 M. Goto and M. Yamano, EP. Pat., 1452537, 2004.153 T. J. Geldbach, P. S. Pregosin and A. Albinati, Organome-

tallics, 2003, 22, 1443.154 N. G. Andersen, R. McDonald and B. A. Keay, Tetrahedron:

Asymmetry, 2001, 12, 263.155 X. Zhang, K. Mashima, K. Koyano, N. Sayo, H. Kumobayashi,

S. Akutagawa and H. Takaya, Tetrahedron Lett., 1991, 32, 7283.156 S.-I. Inoue, M. Osada, K. Koyano, H. Takaya and R. Noyori,

Chem. Lett., 1985, 1007.157 S. Gladiali, A. Dore, D. Fabbri, S. Medici, G. Pirri and

S. Pulacchini, Eur. J. Org. Chem., 2000, 2861.158 N. Aramanino, R. Koller and A. Togni, Organometallics,

2010, 29, 1771.159 W.-C. Yuan, L.-F. Cun, A.-Q. Mi, Y.-Z. Jiang and L.-Z. Gong,

Tetrahedron, 2009, 65, 4130.160 T. Lamouille, C. Saluzzo, R. ter Halle, F. Le Guyader and

M. Lemaire, Tetrahedron Lett., 2001, 42, 663.161 X. Zhang, US. Pat., 2002/0128501, 2002.162 P. J. Cox, W. Wang and V. Snieckus, Tetrahedron Lett., 1992,

33, 2253.163 M. Kant, S. Bischoff, R. Siefken, E. Grudemann and

A. Kockritz, Eur. J. Org. Chem., 2001, 477.164 M. Lemaire, C. Saluzzo and M. Berthod, FR. Pat., 2849037,

2002.165 M. Berthod, C. Saluzzo, G. Mignani and M. Lemaire,

Tetrahedron: Asymmetry, 2004, 15, 639.166 A. Hu, H. L. Ngo and W. Lin, Angew. Chem., Int. Ed., 2004,

43, 2501.167 A. Hu, H. L. Ngo and W. Lin, Org. Lett., 2004, 6, 2937.168 T. Okano, Y. Shimano, H. Konishi, J. Kiji, K. Fukuyama,

H. Kumobayashi and S. Akutagawa, EP. Pat., 0235450,1986.

169 Q.-H. Fan, G.-J. Deng, C.-C. Lin and A. S. C. Chan, Tetra-hedron: Asymmetry, 2001, 12, 1241.

170 G.-J. Deng, B. Yi, Y.-Y. Huang, W.-J. Tang, Y.-M. He andQ.-H. Fan, Adv. Synth. Catal., 2004, 346, 1440.

171 T. Shimada, M. Suda, T. Nagano and K. Kakiuchi, J. Org.Chem., 2005, 70, 10178.

172 X. Zhang, K. Mashima, K. Koyano, N. Sayo, H. Kumobayashi,S. Akutagawa and H. Takaya, J. Chem. Soc., Perkin Trans. 1,1994, 2309.

173 A. R. Abreu, A. F. Peixoto, A. R. Almeida, M. A. O. Lourenço,A. C. B. Neves, J. C. Bayon and M. M. Pereira, Chem. Lett.,2013, 37.

174 A. R. Abreu, M. Lourenço, D. Peral, M. T. S. Rosado, M. E.S. Eusebio, O. Palacios, J. C. Bayon and M. M. Pereira,J. Mol. Catal. A: Chem., 2010, 325, 91.

175 A. N. Hughes and C. Srivanavit, J. Heterocycl. Chem., 1970, 7, 1.176 S. Gladiali, D. Fabbri and L. Kollar, J. Organomet. Chem.,

1995, 491, 91.177 D. Xiao, Z. Zhang and X. Zhang, Org. Lett., 1999, 1, 1679.178 D. Xiao and X. Zhang, Angew. Chem., Int. Ed., 2001, 40, 3425.179 J.-L. Vasse, R. Stranne, R. Zalubovskis, C. Gayet and

C. Moberg, J. Org. Chem., 2003, 68, 3258.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




180 W. Tang, W. Wang, Y. Chi and X. Zhang, Angew. Chem., Int.Ed., 2003, 42, 3509.

181 A. C. B. Neves, M. J. F. Calvete, T. M. V. D. P. Melo andM. M. Pereira, Eur. J. Org. Chem., 2012, 6309.

182 J. N. H. Reek, P. W. N. M. van Leeuwen and A. B. de Haan,in Catalyst Separation, Recovery and Recycling: Chemistryand Process Design, ed. D. J. Cole-Hamilton and R. P. Tooze,Springer, Dordrecht, 2006, ch. 2, pp. 39–72.

183 J. L. Figueiredo, in Catalysis from Theory to Application, ed.J. L. Figueiredo, M. M. Pereira and J. Faria, UniversityCoimbra Press, Coimbra, 2008, ch. 1, pp. 3–32.

184 B. Reuben and H. Wittcoff, J. Chem. Educ., 1988, 65, 605.185 G. J. Sunley and D. J. Watson, Catal. Today, 2000, 58, 293.186 M. Beller, B. Cornils, C. D. Frohning and C. W.

Kohlpaintner, J. Mol. Catal. A: Chem., 1995, 104, 17.187 C. W. Kohlpaintner, R. W. Fischer and B. Cornils, Appl.

Catal., A, 2001, 221, 219.188 R. J. N. Bernier, R. L. Boysen, R. C. Brown, L. S. Scarola and

G. H. Williams, US. Pat., 5453471, 1995.189 Recoverable Catalysts and Reagents-Special Issue, ed.

J. A. Gladysz, Chem. Rev., 2002, 102, 10, 3215–3892.190 D. J. Cole-Hamilton, Science, 2003, 299, 1702.191 Chemistry in Alternative Reaction Media, ed. D. J. Adams,

P. J. Dyson and S. J. Tavener, Wiley, Chichester, 2004.192 Handbook of Green Chemistry and Technology, ed.

J. H. Clark and D. J. Macquarrie, Blackwell Publishing,Oxford, 2002.

193 I. T. Horvath and J. Rabai, Science, 1994, 266, 72.194 G. M. Kramer and F. Leder, US. Pat., 3880945, 1975.195 E. de Wolf, G. van Koten and B. J. Deelman, Chem. Soc.

Rev., 1999, 28, 37.196 A. P. Dobbs and M. R. Kimberley, J. Fluorine Chem., 2002,

118, 3.197 C. R. Mathison and D. J. Cole-Hamilton, in Catalyst

Separation, Recovery and Recycling, ed. D. J. Cole-Hamiltonand R. P. Tooze, Springer, Dordrecht, 2006, ch. 6,pp. 145–181.

198 M. Cavazzini, A. Manfredi, F. Montanari, S. Quici andG. Pozzi, Chem. Commun., 2000, 2171.

199 D. J. Adams, D. J. Cole-Hamilton, E. G. Hope, P. J.Pogorzelec and A. M. Stuart, J. Organomet. Chem., 2004,689, 1413.

200 D. Sinou, D. Maillard, A. Aghmiz and A. Masdeu-i-Bulto,Adv. Synth. Catal., 2003, 345, 603.

201 A. K. Brisdon and C. J. Herbert, Coord. Chem. Rev., 2013,257, 880.

202 D. J. Birdsall, E. G. Hope, A. M. Stuart, W. P. Chen, Y. L. Huand J. L. Xiao, Tetrahedron Lett., 2001, 42, 8551.

203 W. Chen, L. Xu and J. Xiao, Tetrahedron Lett., 2001,42, 4275.

204 G. D. Y. Sogah and D. J. Cram, J. Am. Chem. Soc., 1979,101, 3035.

205 P. Bhattacharyya, D. Gudmunsen, E. G. Hope, R. D.W. Kemmitt, D. R. Paige and A. M. Stuart, J. Chem. Soc.,Perkin Trans. 1, 1997, 3609.

206 W. Chen and J. Xiao, Tetrahedron Lett., 2000, 41, 3697.

207 W. A. Herrmann, C. Brossmer, K. Ofele, C.-P. Reisinger,T. Priermeier, M. Beller and H. Fischer, Angew. Chem., Int.Ed. Engl., 1995, 34, 1844.

208 J. Horn and W. Bannwarth, Eur. J. Org. Chem., 2007, 2058.209 V. Andrushko, D. Schwinn, C. C. Tzschucke, F. Michalek,

J. Horn, C. Mossner and W. Bannwarth, Helv. Chim. Acta,2005, 88, 936.

210 H. Altinel, G. Avsar, M. K. Yilmaz and B. Guzel, J. Supercrit.Fluids, 2009, 51, 202.

211 J. Bayardon, M. Cavazzini, D. Maillard, G. Pozzi, S. Quiciand D. Sinou, Tetrahedron: Asymmetry, 2003, 14, 2215.

212 D. Maillard, J. Bayardon, J. D. Kurichiparambil, C. Nguefack-Fournier and D. Sinou, Tetrahedron: Asymmetry, 2002,13, 1449.

213 M. Cavazzini, G. Pozzi, S. Quici, D. Maillard and D. Sinou,Chem. Commun., 2001, 1220.

214 M. V. Escarcega-Bobadilla, L. Rodrıguez-Perez, E. Teuma,P. Serp, A. M. Masdeu-Bulto and M. Gomez, Catal. Lett.,2011, 141, 808.

215 S. Kainz and W. Leitner, Catal. Lett., 1998, 55, 223.216 G. Francio and W. Leitner, Chem. Commun., 1999, 1663.217 K. Burgemeister, G. Francio, V. H. Gego, L. Greiner,

H. Hugl and W. Leitner, Chem.–Eur. J., 2007, 13, 2798.218 G. Francio, K. Wittmann and W. Leitner, J. Organomet.

Chem., 2001, 621, 130.219 N. Sakai, S. Mano, K. Nozaki and H. Takaya, J. Am. Chem.

Soc., 1993, 115, 7033.220 D. Bonafoux, Z. H. Hua, B. H. Wang and I. Ojima,

J. Fluorine Chem., 2001, 112, 101.221 Aqueous-Phase Organometallic Catalysis, ed. B. Cornils and

W. A. Herrmann, Wiley-VCH, Weinheim, 2004.222 E. Wiebus and B. Cornils, in Catalyst Separation, Recovery

and Recycling, ed. D. J. Cole-Hamilton and R. P. Tooze,Springer, Dordrecht, 2006, ch. 5, pp. 105–143.

223 E. Monflier, G. Fremy, Y. Castanet and A. Montreux, Angew.Chem., Int. Ed. Engl., 1995, 34, 2269.

224 N. Pinault and D. W. Bruce, Coord. Chem. Rev., 2003,241, 1.

225 K. J. Baranyai, G. B. Deacon, D. R. MacFarlane, J. M. Pringleand J. L. Scott, Aust. J. Chem., 2004, 57, 145.

226 M. Kosmulski, J. Gustafsson and J. B. Rosenholm, Thermo-chim. Acta, 2004, 412, 47.

227 J. F. Knifton, J. Mol. Catal., 1987, 43, 65.228 K.-T. Wan and M. E. Davis, J. Chem. Soc., Chem. Commun.,

1993, 1262.229 K.-T. Wan and M. E. Davis, Tetrahedron: Asymmetry, 1993,

4, 2461.230 J. She, L. Ye, J. Zhu and Y. Yuan, Catal. Lett., 2007, 116, 70.231 C. Deng, G. Ou, J. She and Y. Yuan, J. Mol. Catal. A: Chem.,

2007, 270, 76.232 W. A. Herrmann, C. W. Kohlpaintner, R. B. Manetsberger,

H. Bahrmann and H. Kottmann, J. Mol. Catal. A: Chem.,1995, 97, 65.

233 H. Bahrmann, H. Bach, C. D. Frohning, H. J. Kleiner,P. Lappe, D. Peters, D. Regnat and W. A. Herrmann,J. Mol. Catal. A: Chem., 1997, 116, 49.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02




234 H. Bahrmann, K. Bergrath, H.-J. Kleiner, P. Lappe,C. Naumann, D. Peters and D. Regnat, J. Organomet. Chem.,1996, 520, 97.

235 R. W. Eckl, T. Priermeier and W. A. Herrmann,J. Organomet. Chem., 1997, 532, 243.

236 M. Kant, S. Bischoff, R. Siefken, E. Grundemann andA. Kockritz, Eur. J. Org. Chem., 2001, 477.

237 A. Kockritz, S. Bischoff, M. Kant and R. Siefken, J. Mol.Catal. A: Chem., 2001, 174, 119.

238 R. Halle, B. Collason, E. Schulz, M. Spagnol andM. Lemaire, Tetrahedron Lett., 2000, 41, 643.

239 M. Berthod, G. Mignani and M. Lemaire, J. Mol. Catal. A:Chem., 2005, 233, 105.

240 W. Dayoub, A. Favre-Reguillon, M. Berthod, E. Jeanneau,G. Mignani and M. Lemaire, Eur. J. Org. Chem., 2012, 3074.

241 K. N. Gavrilov, S. E. Lyubimov, O. G. Bondarev, M. G.Maksimova, S. V. Zheglov, P. V. Petrovskii, V. A. Davankovand M. T. Reetz, Adv. Synth. Catal., 2007, 349, 609.


Publ

ishe

d on

19

June

201

3. D

ownl

oade

d by

Uni

vers

idad

e de

Coi

mbr

a on

21/

12/2

017

17:5

9:02



chem soc rev · this ornal is c the royal society of chemistry 2013 chem. soc. rev., 2013...

Documents