841

REVIEWS

Preparation of Aryl- and Heteroaryltrimethylsilanes

Dieter HÄBICH, Franz EFFENBERGER* Institut für Organische Chemie der Universität Stuttgart, Pfaffenwaldring 55, D-7000 Stuttgart 80

This review presents a comprehensive survey of the synthetic meth-ods for aryl- and heteroaryltrimethylsilanes. Their preparation can result from direct silicon-carbon coupling reactions, from cycload-dition reactions, or through modifkation of silylaromatic or -heteroaromatic compounds by incorporation 01' further functional groups or by conversion of substituents al ready present.

I. Introduction 2. Direct lntroduction of Trimethylsilyl Groups into Aromatic

and Heteroaromatic Compounds 2.1. Radical Silylation of Aromatic and Heteroaromatic Com-

pounds 2.2. Nuc\eophilic Silylation of Aromatic and Hetcroaromatk

Compounds 2.3. Electrophilic Silylation of Aromatic and Heteroaromatic

Compounds 3. Synthesis of Aryl- and Heteroaryltrimethylsilanes via Cy-

c\oaddition Reactions 3.1. Aryltrimethylsilanes via [2 + 2 + 2)Cycloaddition Reactions 3.2. Aryl- and Heteroaryltrimethylsilanes via [4 + 2)Cycloaddition

Reactions 3.3. Heteroaryltrimethylsilanes via [2 + 3)Cycloaddition Reactions

1. Introduction

The use of silicon in organic synthesis is enjoying a growing popularity due to its various preparative ad-vantages I. The trimethylsilyl group is an especially good example in that it has long been applied as a protective group in the chemistry of peptides, carbo-hydrates, and many other compounds, which can be easily removed. Moreover, it has advantageous ef-fects on the volatility, stability, and solubility of compounds so protected 1• On the other hand, the specific re action of silylated compounds with elec-trophiles (e.g. alkylating or acylating agents) has been only recently systematically investigated. The reactions of trimethylsilyl enol ethers2 are of special interest, because different regio- and stereoselectivity relations can occur than are encountered in the reac-tions of met al enolates. One dass of compounds,

4. Introduction of Substitucnts into the Nucleus llf Aryl- ami Heteroaryltrimethylsilanes

4.1. Halogenation 4.2. lntroduction 01' Sulfur Functions 4.3. Introduction of Nitrogen Functions 4.4. lntroduction of Phosphorus Functions 4.5. Alkylation and Hydroxyalkylation 4.6. Acylation 4.7. Carboxylation 4.8. Silylation 4.9. Protonation 5. Transformation of Substituents in Aryl- and Heteroaryltrime-

thy lsilanes ).1. Nucleophilic Exchange of Halides 5.2. Functionalization of Carboxylic Acid Derivatives 5.3. Functionalization of Hydroxy and Amino Groups 5.4. Condensation Reactions 5.5. Oxidation Reactions 5.6. Reduction Reac!ions 5.7. Metal Complexes of Aryl- and Heteroaryltrimethylsilanes 5.8. Miscellaneous 6. ConcIusions

whose mode of reaction towards electrophiles is es-pecially interesting, is the aryl- and heteroaryltrime-thylsilanes. Since reactivity and selectivity of C H and CSiR3 bonds differ significantly, isomers that are difficult to obtain by conventional electrophilic aromatic substitution (normally deprotonation reac-tions) can, in some cases, be more conveniently pre-pared by desilylation reactions3•

fYH ~ + E-X

R

fY1

E --~) ~ + HX

R

deprotonation rcaction

E-X

desilylatiofi reaction

842 Dieter Häbich, Franz Efl'enberger

If desilylation ft~actions are to be of wide preparative importance in the chemistry of aromatic compounds, a simple access to the corresponding aryl- and heteroaryltrimethylsilanes is necessary. Apart from an older Japanese paper4, no review of the prepara-tion of this class of compounds exists. One finds ref-erence to the preparation of arylsilanes 5. 6. 7 only in connection with general publications on organosili-con compounds.

We intend to give a survey of C-trimethylsilylated aromatic and he:teroaromatic compounds. The litera-ture through 1977 has been reviewed. Compounds which carry, be:sides the trimethylsilyl group. other group IV substituents (e.g. R3Sn) are not included, since they undergo electrophilic reactionsX at the po-sition bearing the substituent more easily than aryl-trimethylsilanesJ .

2. Direct Introduction of Trimethylsilyl Groups into Aromatic and Heteroaromatic Compounds

In principle, trimethylsilyl groups can be introduced into aromatic or heteroaromatic compounds in a ra-dical, nucleophilic, or electrophilic manner.

2.1. Radical Silylation of Aromatic and Heteroaromatic Compounds

The silylation of aromatic compounds via free radi-cal processes can be induced thermally, photochemi-cally, or by other radical sources. Aromatic com-pounds react with silicon hydrides in the gas phase at 500-85009

, in the liquid phase under autogeneous pressure at 350--50009

, and in the presence of perox-ides at 135 cl 10: gas phase condensations 11 and reac-tions via electrical discharge 12 have also been re-ported with silicon halides.

Ar-H + H-SiR3

Ar-H + X-SiR3 Ar-SiR3 + HX

The reactions 01' aryl halides with silicon hydrides in the gas phase at 500--700" t1 and in the liquid phase at 350-450 U x also afford arylsilanes. Disilanes that can be thermally split into silyl radicals react in the same wayl4. All these reactions are of high encrgy

1

hv ~

SYNTlIESjS

consumption, give mixtures of products, and thus have limited laboratory use. Their usefulness is fur-ther reduced because the yield of arylsilanes de-creases with increasing number of methyl groups in the SiXrresidue. Since the reactants are readily ob-tainable, however, these methods ofpreparation may be of industrial i mportance.

Silyl radicals can also be obtained radiochemically (e.g. yl" eO lb) and show, in principle, the same mode of reaction with aromatic compounds as those in-duced thermally. U.V.-Irradiation of aryl halides in the presence of aimethylsilane produces aryltrime-thylsilanes along with other products in various yields, e.g. phenyltrimethylsilane (11 '+"6) 17 or penta-fluorophenyltrimethylsilane (53%)1~.

Pentaßuorophenyltrimethylsilane' ': HCKat1uorobenzcne (' 8.6 g, 0.1 mol) and trimethylsilane (7.4 g, 0.1 mol) are irradiated (U.V. light) with shaking tin 240 h in a 300 ml sili~a tube. The tube is cooled to - 196' prior to opening. Trime-thyltluorosilane is serarated by fractional condensation and the rc-maining liquid is distilled to givc heXl!!7uorobenzene; yield: 9.1 g (49'\,): b.p. 80-82" andpenta!7uorophenyltrimethrl.\ilane: yidd: 6.5 g (53% based on hCKat1uorobenzcne consumed): h.p. J70".

Aryltrimethylsilanes are also produced by the U.V. photo lysis of bis[trimethylsilyl]mercury in aromatic compounds as solvents, though usually only in mod-erate yields I9,2!J,21.

X : H, F

hv ~

Ar-Si(CH313 + (H3ChSiX + Hg + other products

In the photolysis of substituted disilanes 1 [R I = H, CH), f-C4H9 ; R 2, R 3 = H, CH), CbH" Si(CH1hl, reactive intermediates 2 are formed by a (1,3]sigma-tropic rearrangement. In the presence of trapping agents such as 3 [Y =ce CH2, 0; R 4,,,, H, CH3, f··C4H 9;

R5 o=.CH), Si(CH3h C(CH1)CH2, etc.] or 4 [R 6 =H, Si(CH3h; R7 =H, t-C4H9 , Si(CH3h, C6 H5],

intermediate 2 undergoes addition reactions to give the aryltrimethylsilanes 5 or 6, respectively22.

In contrast, photo lysis of 1 in the presence of dime-thyl sulfoxide takes a different pathway. Here, the

)

November 1979

products are found to be disiloxanes, arylsilanes [among these are aryltrimethylsilanes (56-57%)], di-methylsilanone, and dimethyl sulfide23 •

2.2. Nucleophilic Silylation of Aromatic and Heteroaro-matic Compounds

The reaction of triorganosilylmetal compounds24

with aryl and heteroaryl halides leads to triorgano-silylaromatic compounds.

M = Li, Na, K

The preparative value of this reaction using iso la ted trimethylsilyllithium 25, -sodium25, and -potassium25

is limited, due to the instability of these compounds and to the possibility of a met al/halide exchange (formation of disilanes). This method has gained sig-nificance only through the in situ formation of the si-lylating agents from hexamethyldisilane with appro-priate bases. The reaction of aryl halides 7 with the disilane in this way gives aryltrimethylsilanes 8 in yields of 63-92%26.

7

X' = H3C, Cl x2 = Cl, Sr, J MY = LiCH3, NaOCH3, KOCH3

HMPT )

8

2-Pyridyltrimethylsilane is similarly obtained from 2-bromopyridine, the disilane, and potassium me-thoxide in 80% yield 26. The exact mechanism is still uncertain, although an aryne pathway can be ex-cluded because of the distribution of isomers ob-tained. Cleavage of hexamethyldisilane with aryl halides 9 under the catalytic influence of tetrakis[tri-phenylphosphine]palladium(O) affords similar prod-ucts 10. This reaction is especially important for the preparation of nitrophenyltrimethylsilanes, since the nitro function is destroyed by all other silylating methods (Table 1).

9

10

Pd[P(CsHsh]., 140-160°, 40-90 h

)

Preparation of Aryl- and Heteroaryltrimethylsilanes 843

'fable 1. Aryltrimethylsilanes 10 via Palladium-Catalyzed Cleav-age of Hexamethyldisilane with Aryl Halides 9

Substrate 9 Yield [''<.) Refer-No. X R' R' RJ of 10 ence

a CI H H H 98 27 b Br H H H 99 27 l' Br H H H,CO 39 27 d CI H H O,N 61-100 27,28 c CI H (),N H 53 28

Br H (),N H 35 28 g CI O,N H H 65 28 h CI O,N 11 O,N 40-51 28.29

2-Nitrophenyltrimethylsilane (1 Og)2x:

A mixture of 2-nitrochlorobenzene (4.37 g. 30 mmol), hexamethyl-disilane (8.78 g, 0 mmol). tetrakis[triphenylphosphine)palla-dium(O) (0.35 g. 0.3 mmol), and xylene (15 ml) is heated in a pyrex tube at 150 u for 40 h with stirring. The mixture is diluted with pe-troleum ether to precipitate the catalyst, which is removed by filtra-tion. Evaporation of the filtrate and subsequent distillation gives lOg; yield: 7.81 g (65'lf;); b.p. 115-117'/10 torr; n;:': 1.5325.

Aryl iodides form stable adducts with the palladium catalyst and therefore will not react in this wayn. Reaction of hexamethyldisilane with dihalobenzenes produces halophenyltrimethylsilanes and bis[trime-thylsilyl]benzenes3o. 31 •

The reductive silylation of aromatic compounds is also an example of the nucleophilic-type reaction. It differs from the reactions of aryl halides discussed above because of the lack of an anionic leaving group. Consequently, cyclohexadiene derivatives 12 are formed by an addition re action from aromatic compounds 11. They rearomatize in a subsequent elimination step often achieved by the introduction of air (Table 2) to 13. Even without introduction of air, smaller32 35 or larger35•36 amounts of 13 are formed together with the adducts 12, depending on the reaction conditions.

11 12

13

1.4-Bis[trimethylsilyl)benzene (Ba) from Benzene I': Method A: Indirect: Benzene (I mol), tinely cut lithium (3 mol). chlorotrimethylsilane (4 mol), and tetrahydrofuran (250 ml) are stirred for 12 days at room temperature in an inert atmosphere. After the mixture has been filtered and volatile products removed in vacuum. product 12a (609,,), contaminated with about 5% 13a. cry,tallizes. The product mixture in carbon tetrachloride is weil ,tirred during the introduction of air to yield Ba quantitatively.

844 Dieter Häbich, Franz. Effenberger

Method B: Direct: Performed as abovc except with immediate in-troduction of air after which Ba is isolated by distillation aud re-crystallization; yield: 65%, rn.p. 98".

Table 2. Reductive Silylation of Arenes 11 with Lithium/Chloro-trimethvlsilanea in Tetrahydrolilran to 12 and SubselJucnt Air Oxidatilln b to 133415 .

Su bstrate 11 No. R'

a H b H3C l' H,C d H e ILC f file g i-C,H;

R' R1

H H H H Ihe H H,C tbC H H,C H,C H,C H 11

Yield [%1 01' 12'

60 ~:5

67 30 75 ~()

70 75 5

50

a lJse of magnesium/chloTotrirnethylsilane in hexamethylphos-phoric triamide results in lower (1O··25'!{,) yiclds of 12" ".

b Only papers which indude this rearomatization step are li,tcd. " Yield of 12·., 13 almost quantitative in each case.

Naphthalenes and anthracenes do not reaet with me-tals and chlorotrimethylsilane as specifically and usually give poorer yields than the benzene deriva-tives 1131.3X .. <o.411.

Besides the 1,4- and 1,2-adductsJx• monosilylated ad-

ducts40 are formed; also, the rearomatization step often requires special conditions1942

• Despite the above mentioned disadvantages. reductive silylation is the best known method for the preparation of so me sensitive compounds (e.g. trimethylsilylanthra-cenes). Biphenyl reacts with an excess of sodium/ chlorotrimethylsilane to form a complex mixture of silylated isomers4J .

It has been demonstrated, by investigations dealing with the mechanism of reductive silylation, that se-quences of radic~tl anion intermediates and not di-anions are involved 32

•3H

• The reaction of chlorotri-methylsilane with highly activated magnesium in te-trahydrofuran at - 10' to give trimethylsilane or hex~methyldisilane is assumed to be proof 01' the existence ~)f organosilyl Grignard compounds44 . The general mode of reaction 01' the system metal/chlo-rotrimethylsilane/donor solvent with various 1'unc-tional groups has been reviewed45. Under the condi-tions 01' reductive silylation, reactions 01' aromatic al-dehydes, keton,:!s. esters, imines, and nitriles lead to product mixtures that can be derived from radical anion sequences45

. Thus, 1'rom reaction of benzoni-trile, the tetrakis[trimethylsilyl] compound 14 is ob-tained wh ich, upon the hydrolytic work-up. afförds the benzylamine 15 (64~(,)46.

A variant 01' the reductive silylation, which affords better yields and homogeneous product 1'orma tion. especially with naphthalenes, requires the use 01' 1-trimethylsiloxynaphthalcne (16). The primarily formed adduct 17 rearomatizes to 18 with the elimi-nation 01' hexamethyldisiloxane47

•

o-CN

14

16

18

SYNTIlFSIS

H20/HEll/OH8 -----7

15

17

Special conditions have been found with o-methoxy-aryloxazolines that permit the cleavage of the methoxy group, in proximity to a potential carboxylic acid function, with trimethylsilyllithium or the cor-responding Grignard compound by nucleophilic substitution 01' the methoxy group4X. The addition of alkyllithium compounds to styrenes and subs,~quent treatment with chlorotrimethylsilane a1'fords alkyl-phenyltrimethylsilanes (18-85%)4".

2.3. Electrophilk Silylation of Aromatic and Het,eroaro-matic Compounds

The direct introduction of silyl groups into aromatic compounds via anormal electrophilic substitution has not yet been achieved. Even such reactive sub-strates as phloroglucine trimethyl ether or 1,3,5-tri-pyrrolidinobenzene5() have not afforded C-silyla-tion 51 with either chlorotrimethylsilane or the even more reactive trimethylsilyl trifluoromethanesulfon-ate52 • Not even by addition 01' Friedel Crafts cata-lysts can this re action be ef1'ected5.~. The instability of silylenium ions [R3SrtJ p4.55.5h may be one reason for this behaviour, hut the very easily occurring reverse reaction [protodl!silylation, which can be used for the simple prep.uation 01' compounds of the type (CH3)3SiXj57, is more decisive. When the reverse reaction is excluded (for instance by the irreversible removal 01' hydrogen) direct silylation of aromatic compollnds witl: boron trichloride as catalyst oc-curs5H

•

November 1979

Despite this fact, electrophilic introduction of silyl groups into aromatic and heteroaromatic com-pounds is the most important preparative method for this dass of compounds. However, instead of the aromatic compounds, their considerably more nu-deophilic organometallic derivatives are usually al-lowed to react with chlorotrimethylsilane or similar silylating agents.

2.3.1. Preparations via Organomagnesium Compounds

Many aryltrimethylsilanes have been prepared by conventional Grignard reactions [i.e. defined forma-tion of the Grignard compound and subsequent sily-lation (Table 3»). The use of cyanotrimethylsilane or ethoxytrimethylsilane60 instead of chlorotrimethylsi-lane are exceptions.

Ar-X + Mg

Table 3. Aryltrimethylsilanes via Conventional Grignard Reac-tions

Ar· X

OBr

° OBr

o-{}sr

Br

~ ~

H3C-{}Br

i-C3H7-{}sr

ICzHs 13 Si-CHz-{}sr

IH3 CI3Si-CHz-{}Br

Sr 0--0

Yie1d [%]

41-92

76

60

41

50

80

56

78

80

71

84

76

Reference

72-77

77

78

70

61

61, 72, 76

61, 79

80

80

81

81

81

81

82

Preparation 01' Ary1- and Heteroaryltrimethylsilanes 845

Table 3. Continued _._----------------_ .. _------~ X Y~d Reference

[%] -----_ .. _------_._-----

HZC=CH-oCI 70

H3C H2C=b -oCI 71

F3C

~sr 65

F3C

Cl:OBr

IH3C1 3Si-{}CI 60-80

sr-{}Br 93'; 52-80

Ar-O H3C-~i-~Sr

I "=..r Ar-O

H3co-{}Br

Br

0 0-0 o-0-{}sr

14- 41

36

86

42- 81

o-CH2-0-{}Br 88

Br-{}CHz-o-CHz-{}sr

H3c-s-{}sr 65

o-S-{}Br 60

IH3ChSi-O-{}Sr 77

C.Hg-/

IH3C13Si-0-Qsr 62

C.Hg-/

F-{}Br 68-91

F F F~sr 35

F F

CI 6J Clh OJ

22-41

45

75

90

52

65, 81", 83"

84"

85, 86

86

87, 88, 89

67', 72, 76, 87, 105

90

91

92

93, 94, 95

7

96

97

94

62, 63, 64

98

72, 76, 99

18, 100

61, 101

99, 102

61, 91, 103, 104

61, 72, 76, 105

106

846 Dieter Häbich, Franz Effenberger

Table 3. Continued ---- -- ---------------_._- . - ._---_ .. _------

Ar- X

CIX~ Re, Cl Cl

Br

O-Br

Br--(.S),-Br U

Yield 1%)

80

50

a Polymers of product are also formed.

Refercnce

107

108, 109

110, 111

h Several trimethylsilylpolyphenyl ethers are also formed. e Bis[trimethylsilyl) product formcd.

Diethyl ether is usually used as the solvent, although tetrahydrofuran is finding increasing use. Since the formation of Grignard function in sterically hin-dered positions (o-silylation) occurs only with difli-culty, the ether can be replaced by some higher boil-ing solvent after the reaction has been started, to af-ford better yields61

• FUIlctional groups that react with Grignard reagents have to be protected, e.g. phenols by O-silylation62.63.64 or carbonyl groups by acetalization. An example for the preparation of 4-acetylphenyltrimethylsilane (19) is illustrative65• 66•

1. Mg 2. (H3C)3Si Cl

3. H$/H20 )

TI

H3C~'Br

19

Haloaryltrimethylsilanes are obtained by selective silylation of polyhaloaromatic eompounds, in the course of which the different reactivities of C X bonds (J> Br > Cl> F) towards magnesium are uti-lized. By using an exeess of magnesium and chloro-irimethylsilane it is also possible to achieve bis-silylation67,6x. The introduetion of the trimethylsilyl groups via the trichlorosilyl compounds6 I.o9,70.71 is less often used but is illustrated by the preparaticm of l-naphthyltrimethylsilane (20)NI.

2. SiCI, --~)

20

In so me eases inert aryl halides which do not react weil under conventional Grignard conditions can be converted to aryltrimethylsilanes in better yields by

using the entrainment method l12 (du ring the re action so me alkyl bromide is continuously added as an en-trainer to keep the magnesium surfaee aetive (Table 4).

Table 4. Silylation 0" Aryl and Heteroaryl Halides via the Entrain-ment Methud

Aryl Halide

Ob-Br

60Br

fS(;rBr

CH 3

cA;rBr

Br,

O-ö OCH2-{}Br

Cl

OCH2~

"I fi oq Br

Q Br

OS-{}Br

rjB' '/ 'N

H3C N

'q-{}B' CH3

Br Br

Bri:tsr

Br Br

O~Br < "I 0

Entminer

Br-CH2-CH2-Br

Br-CH2-CH 2-Br

Br --CH2'-CH2-Br

Br-CH2-CH 2-Br

Br-CH2'-CH2-Br

Br-CH2-CH2-Br

Br-CH2'-CH2-Br

Br-CH 2'-CH2-Br

C2HS-Br

Br-CH 2-CH2-Br

C2Hs-Br

Br-CH2-CH 2-Br

C2Hs-Br

Br-CH2--CHcBr

Yield Reference [%)

51 113

10 113

25 114, 115

31 115

116

41 113, 114

21 97

114

50 117

60 114

118

80 119

87" 120

121

"--'--~------------------_ .. '--"~----

" Only thc mnno-,il:'lated product is fnrmed.

The separate pn:paration of the organometallie in-termediates is orten accompanied by disadvantages (e.g. isomerizatiern, decomposition, more difficult 0-

silylation, ete.). These obstacles are reduced by bringing together the aryl halides with magnesium and chlorotrimethylsilane in a one pot re:action. The advantages 01' such an in situ procedure 122 have be-come obvious in the preparations of polysilylated benzenes 123.124 and naphthalcne3 l<, 2-halo- ' ?'i· 1 ~h. 127,

and some other phenyltrimethylsilanes l2x as weH as in the reactiom of 2-chloropyridine 12lU 2'1, L10 and

November 1979

-quinoline 13O• Particularly advantageous - even with sterically hindered compounds - is the in situ Grig-nard synthesis of aryltrimethylsilanes in hexamethyl-phosphoric triamide as solvent, as demonstrated by a recent publication wh ich gives a comprehensive sur-vey of the applications and limitations of this proce-dure (Table 5)131.

Table 5. In Situ Grignard Synthesis of Aryl- and Heteroaryltrime-thylsilanes from Halides using Magnesium/Chlorotrime-thylsilane/Hexamethylphosphoric Triamide ,,,

----------------,-------

Aryl Halide

OCI OB,

CH3

6 CI

t>--O-B'

Yield [%1

87

88

80

85

81

B3

85

62

49

5B

74

80

67

31

77

2-t-Butylphenyltrimethylsilane' ":

Aryl Halide

F-(}B' CI-(}J F3C OB,

O-(}B,

O-(}B' C)-CI

Ö-Br

N~B'

)0-Br Br

Yield [9<,)

61

67

76

33

71

73

75

74

41

75

72

76

62

78

32

49

78

Magnesium (1.46 g, 0.06 mol), dry hexamethylphosphoric triamide (40 ml), and chlorotrimethylsilane (8.62 g, 0.08 mol) are placed in a two neck, round bottom flask equipped with a dropping funnel, condenser. and drying tube (phosphorus pentoxide). To this, a few ml of a solution of 2-t-butylbromobenzene (9.5 g, 0.044 mol) in dry hexamethylphosphoric triamide (15 ml) are added, the mixture is warmed unti! the contents begin to foam, and then the reaction is initiated by adding a few drops of 1,2-dibromoethane. The rest of

Preparation of Aryl- and Heteroaryltrimethylsilanes 847

the aryl bromide solution is added with stirring within 5 h at 80". stirring is then continued for 45 h at this temperature. After cool-ing, the reaction mixture is hydrolyzed by pouring into a 0.5'\> sodi-um hydrogen carbonate solution (250 ml). in the course of wh ich the neutrality ofthe solution is testcd. After the neutral mixture has been filtered by suction. the silane is extracted with ether. washed with water. dried with sodium sulfate, and fractionated; yield: 5.3 g (58''',); b.p. 120°/130 torr; n;;'; 1.5143.

2.3.2. Preparations via Organolithium Compounds

Organolithium compounds are differentiated from the Grignard compounds by their greater reactivity and lesser steric sensitivity. The various procedures differ only in the preparation of the required lithium intermediate.

The reaction of aryl halides with metallic lithium. a method which is convenient in most cases only for less sensitive compounds (Table 6) has the dosest similarity to the Grignard synthesis. Normally chlo-rotrimethylsilane is used as the silylating agent but in some cases the bromo and ethoxy derivatives have also been em ployed 74.132, t33.

Ar-X + 2 Li Ar-Li

Table 6. Aryltrimethylsilanes from Aryl Halides using Metallic Li-thium/Chlorotrimethylsilane

Aryl Halide

X "

~ ~

d H3

~J CH l

H3C

HlCOB,

Yield Reference [%]

67 108, 134, 135

70 136

67 108, 134

31-84 91, lOB', 134'

53-72 75, 91, 108, 134, 137

55 - 66 134', 138

41-69 134", 138

55-77 134", 138

72-75 134", 138

65-74 134", 138

848 Dieler Häbich, Franz Effenberger

Table 6. Continucd

Aryl Halide

Br

o-d B'h IliB' ~

IliOCH3

OB,

IH3C11N-G-Br

[IH3C13Si)1N-G-Sr

Yield [%1

36- 65

75

n b

83

71

36

40- 55

30

45

46- 84

29-79

53

Reference

134", 138

139

139

140

141

91

91, 141

142

143

91, 143 -146

91, 137, 144, 145

147

aHalide used for the preparation of the aryllithium not speci-lied.

b Bis[trimethylsilyl] product obtained.

3-Dimethylaminophcnyltrimethylsilane 144:

To !inely cut lithium (5.6 g, 0.81 mol) suspended in ether (100 ml), a solution of 3-bromodimethylaniline (70 g, 0.35 mol) is aJded with stirring over 2 h. The mixt ure is heated under reflux !l)r 30 min, then a solution of chlorotrimethylsilane (37 g, 0.34 mol) in ether (75 ml) is added over 1 h. Stirring and heating under reflux are continued for 2 h. The reaction mixture is hydrolyzed, the ether layer separated, and dried with drierite. The mixt ure is !iltered and the ether evaporated under reduccd pressure. Distillation affords a colourless product; yicld: 56 g (84%); b.p. 109-11O'~ 18 torr; n;~': 1.5265.

Halide/metal exchange reactions present a further possibility for the preparation of aryllithium com-pounds.

Ar-Si(CH313 + LiCI

The discrimination of reactivity of the C X bond (J>BI>CI>F) towald n-butyllithium enables a se-lective exchange with polyhalogenated aromatic compounds (Talble 7).

SYNTHESIS

Table 7. Aryltrimeth:tlsilanes via Halogen/Metal Exchange with n-Butyllithil m aud Subsequent Rcaction with Chlorotri-methylsilane

Aryl Halide

Br

60

~ ~ (~ ~ o

~Br

~ o

Br roOH "'I " " ./

~OH

~ Br

QO Br

Br m Br(:x>

C'ID y Br

\0~ ~Br

Sr

(j)j

Yield [%]

30

27

83"

46

46

58

58

35

20

53

48

70

50

72

67

70

36

Reference

113

148

149

'77

77

77

77

150

150

150

150

151

152

152

152

152

94, 114

48 94

51 94

November 1979 Preparation of Aryl- and Heteroaryltrimethylsilanes 849

Table 7. Continued Table 7. Continued

Aryl Yield Reference Aryl Yield Reference Halide [%] Halide [%]

S 6-

CH3 f5J(;rBr 50-71 94, 153 '/ \ Br 64 97

S rl 3C-S-Ö-Br ~ 64- 80 94, 153 65 97

Br 5 IHO-CH2-CH2)2 N

O (9) 45 94 '/ \ Br 51 160

Br 6-SiICH3)3 C2HS '/ \ Br 97 I N

~ 77 94 IHJChSi-s-Ö-Br 20- 80 97, 161 Br

~ Br-Ö-0-Ö-Br 77a 162 '/ \ I" Br 68 115 - - d-H2-CH2-NIC2HS!, N '/ \ Br 80 163 OBr 24- 39 129, 130, 154

CI

{}-Br 37- 39 129, 130 OBr 62 91

ro CI CI 49 130

CI*CI "- "Br 48, 44 a 164, 165, 166a

CQ CI CI

"- " 36 130 CI CI

Br IH 3ChSi*CI 167

OBr CI CI

'/ 'N 91, 90" 155, 342 Br

Br OBr 17 85, 168

OBr Br-Ö-Br '/ 'N 69" 342 47-79 145, 169, 170

Br Br

0--OBr 37-65 77 ~J 33 108

Br

H3C-D--O-Br 64-78 156, 157, 158

d-

0OH

'/ \ Br 57 168 H3C0-O-O-Br 43 157

CI F

CI-O-O-Br F*,CI 171 b

72-80 156, 157 F F

CI Cl F

6-o-Br 65 156 F*,CI 87 171b

B,-D--O-Br Cl F

43 157 CI Cl CH Cl CI

t- C4H9-CH2b- CI*~i*CI 17 a 167 '/ \ Br 70 159 Cl CI CH3 CI CI

t-C 4Hg-CH2-Ö-B, 80 159 *9H3

9~* CI '/ \ 5i-O-Si I \ CI 13a 167 t-C4H9~

- I I -:-CI CI CHl CH3Cl Cl

'/ \ J 108 CI-QCI 80' t-C,Hg ~ !. 172

H3C0o-CI Cl

'/ \ Br 27 108 ., Bis[trimethylsilYll product obtained. H3CO h Use of excess n-butyllithium and chlorotrimethylsilane results in ~.~-~--_.-.-

~~~--------- lormation of polytrimethylsilylated products.

850 Die1:er Häbich, Franz Et1enberger

The more strongly acidic C H bonds of heteroaro-matic compounds such as, für example 21, can be metallated directly by treatment with organolithium compounds and subsequently silylated to yield si-lanes 23 without the need for the intermediate halo-genated compollnds (Table 8).

Table 8. Heteroaryllrimethylsilanes 23 via Hydrogen/Metal Ex-change in 21 with n-BlItyllithium and Subsc4uent Silyla-tion

Substrate 21 R'

H H If

Y

o o S

z

CII C Hr CII

H,C S (H,C),N-SO, S (C2H,),N SO, S

CH CH CH

Br H (C1H,OhCII

C~,><CH3

(C2H,OhP(0) 11 II

S S S

S

CH CCOOH CH

CH

S CH NH CH N CH, N

Yield lW,] Rcference 01'23

72 41 79

93

96

31 23 40 3356

lJ4 173 94. 117

175 176 176 173 173 177

177.178

179 IXO, lXI IX2. 1~3

a Lithium diisopmpylamide is lIsed as metallating agcn!.

In this manner, 2,5-bis[trimethylsilyl]thiophene (65%) is obtained [rom thiophene 175 by reaction with two mol of butyllithium/chlorotrimethylsilane and N-methyl-1 ,4-bis[trimethylsilyl]imidazole (32%) may be prepared from N-methylimidazolel~2. This meth-od of silylation is also applicable to benzo-annelated systems, e.g. benzothiophene Y4. 114, -thiazole I X4. I X"

and -imidazole m .183.

Trimethyl-( t -methyl.2-imidazolyl)-silane 'Xl: I-Methylimidawlc (9.5X g. 120 nlIlJol) is ,Iowly addcd (dropwist') to a hexane solution 01 n-blltyllithillm (120 mmol) in ether (150 ml). After hcating under reflux tin I h. chlofotrimethyhilallc (13.('.~ g. 120 mmol) is added, After 2 h 01' stirring. the reactioll mixture is liltcrcd. thc solvent t:vaporated. and the silane isolated by vaC'lllm distillation; yicld: 10J g (56%): b.p. 92"i 10 torr.

Besides the heterocyclic compounds 21, benzene der-ivatives 24, in which ortho-metallation 1X6 is favoured by appropriate substituents, can also bc metallated directly and subseqllently silylated to afti.lrd aryltri-methvlsilanes 2c, (Tahle 9).

SYNTIIESIS

25

26

Table 9. Aryltrimcth~ lsilanes 26 via orlho- Metallation 01' Bcnzene Derivatives 24

Substrate 24 Yidd ('Ii'] Referencc R' R2 x of 26

fI Ii OC"II, 6271 93.94. 114 H H SC,,1-I, 23 94. 114 F H OCH, 13 187 CI H OCH, 60 IR? Hr 11 OCH, 44 187 J H OCH, 58 187 H H eH, N(CH'll 60 188 Ii 11 CO NB (;'.11, 60 189 H H qOSi(CH,hl-- CII) 9()" 190 H,C H qOSi(CII,J'] CH, 71·Lh 190 H 11 1e ero ~i(Cll;)d CH, 90' 190

" n-Butyllithium/tetr.lmcthylethylcncdiamine used as metallating agent.

h Two produds arisir g from dimetallation also formed (yield: 1 (l\'[) each).

The intramoleClllar complexation of the lithium compound 25 is decisive. Since the complexation is also possible with the other ortho-position, bis-sily-lated compounds, such as 2,2' -bis[trimethylsilyl]di-phenyl ether (609)162 or 2,6-bis[trimethylsilyl]-N,N-dimethylbenzylanine (85%)IXX, can be produced se-lectively. In the cases of phloroglucine trimethyl eth-er 191 , methoxy-m.phthalenes 150, and dibenzofuran94

reaction can be brought about specifically. Aromatic compounds without such C H bonds react to form mixtures of isomers 192.116. Thus polymetallation/si-lylation reactions of aromatic compounds such as bi-phenyl, anthracene, fluorene etc. with butyllithiul11/ tetramethylethylenediamine/chlorotrimethylsilane are of no prepara tive importance I '13.

There is the possi bility of a compet.ition between me-tal/halogen exchange (formation >l)f 28) and metall hydrogen exchange (formation of 29) in the ca se 01' the polyhaloarOll' atic cnmpounds 27 ('fable t(».

Once again polysilylated prmlucts are fonlIed when an excess of organolithium compound (R :iLi)/l~hlo­rotrimethylsilane is employed I ')4. 1"1. 190 I')','.

November 1979 Preparation 01' Aryl- and I-Ieteroaryltrimethylsilanes R5t

Table 10. Competition 01' Metal/llalogen and Metal/llydrogcn Exchange in Plllyhaloaromatk Compounds 27 -_ .. -~-- ------ ~----~------,-------------------

Yield [9,,) 01' Rderence

R ' R' R' R 4 X R' 28 29 -~-------'-"------'-----'-----'--- . - ~- ._---- ._- - . --- --"-~----~~- -_ .. _-- "------_._-------._--

CI H CI CI CI /-C,H" 100 165, 1')4, 195 CI H CI CI CI n-C4 11" 71 29 165,194, 195 CI H CI CI CI C"H, 10 90 165, 194, 195 CI H Cl CI CI CII, 7 93 165. 1<)4. 11)5 CI H H CI CI I-CII" 100 194, 11)5 CI H H Cl Cl n-C4 H" 65 35 194. IlJ5 Cl Cl Cl Cl CI I-C411" 38 45" 11)4 CI Cl CI CI CI n-C4 lt, 95 194 F P Br F F n-C4 lt, 87 196 H F F H F /I-c',lt, 197

_ .. _- ._. ~-----~--------~. -~ -- - - ~---_._-_._-- ---" ---~---~---

a 3,6-Bis[trimethylsilyl]-1,2,4,5-tetrachlorobenzene [29: X -e Si(ClI,)" R' _ R' =e R' = R" =e Cl] also formed in t7~:' yield. h Mono-, bis-, and tris[trimethylsilyl] compounds are tllfmed.

27

1. R5 U 2. IH3ChSiCl

)

28

and/or

29

2.3.3. Preparations via Organosodium Compounds

Organosodium compounds are even more reactive and sensitive than the comparable lithium deriva-

tives. The silylation is therefore normally carried out in a manner analogous to the Wurtz-Fittig reaction and not by the use of isolated sodium eompounds. Ether, benzene, toluene, or xylene ean be used as sol-vents. The rigorous reaetion eonditions allow only for the presenee of inert substituents (e.g. alkyl-, aryl-, alkoxy-, aryloxy-, R)Si-groups ete.). Phenols and anilines have to be proteeted by 0- or N-silyla-tion, respeetively before the Wurtz eoupling reaetion can be performed (Table 11).

30 31

Table 11. Aryltrimethylsilanes 31 via Wurtz Coupling 01' Aryl Halides 30 with Chlorotrimcthylsilane/Sodium/Solvent ._-~----------------_._._._--- ._------_._----_._--_._--~

R' R2 R 3 R 4 X Solvent Yield [%] Refcrence of 31

-------------------------_._----_. ---------_._-- .. _------------ -------~----------H H H Il CI toluenc" or 6590 102,200.201

ether /

H Ö 11 Hr toluene 27 94

CH, H H 11 CI toluenc 68 16l1. 102 H CH, H 11 CI toluenc, 55 85 61,201".202

ether",or xylene

H H CH, H CI toluene 1'.7 102 CH, 01, H 11 CI hen7cne or 74 203.204

toluene CII, H CH 3 11 CI toluene 20} CH, If H ClI, CI toluene 203 CH, 1I H CII, Hr benzene 74 204 H CII, CHI 11 CI ben/elle or 75 203.204

toluelle 11 CII, 11 CII, Hr hen/ene or gj 2OJ. 204

tolucnc H C.,1I., 11 H CI ether" 50 2111"' 11 CII, H C.,I!, Br ethl~r 77 IU~ H I-C,II; 11 11 HI ether 7<, 2UI 11 i-C,H. 11 i-CII, Hr IO~

852 Dieler Häbich, Franz Effenberger

'fable 11. Continucd

R'

11

H

er.II, H (H,C),Si 11 11 H H H

11 H H,CO H H

H

(H,C)$iO H 11 (H,C),SiO H (H,C"SiO

J{'

H (CIl,), (CII,), (nh)4

11 C,JL H (H,C),Si 11 11 11 II,CO

H,CO 0

11

" H

H

H (1I,C) ,SiO H H C"II. C.II.,

R'

H

t-C,H'i H H H 1I 11 Il H (11,ChSi 4-(H,ChSi C,.H, 4-Br C,,1I 4

11

H,CO (CII,ll 0

H C"B,., , ,(Y C"II,O (H3ClJSi- O-CH-CH, -0-

I CH3

H H (JI,C),SiO (11.,ChSiO (H,Cj,SiO 11

11 [(lI,C"SibN H ---"------~- - -----_. -_ .. _--,-

.• Slldium suspension. " Bisltrimethylsilyl/ prnduct f()rmed. , n 04,8, 12, 14. 16. IS.

H

H 11 11 11 H H H H I! 11 H 11

H H (1I,C),Si 11 11

" 11 H H 11 H

" 11

1- and 2-Chloronaphthalene]12 as weil as various chloro- and bromophenanthrenes 1 tl react in a simi-lar way. The partial re action of polyhaloaromatic compounds is not possible: either all halide atoms react213 or the molecule does not undergo a Wurtz coupling61 . Numerous 2,4,6-substituted silylated phenols have be,;!n prepared according to this meth-Od214,21'.

o-'J·oh.ltrimetbvlsilllIlC ! I •. ,: o-Chl;lrotllluel;c (502.5 g. 3,95 mol) is mixed wilh l'hlorotrimeth}lsi-lane (see below) ami added slowly to molten sllJium (11)5 g. 8.5 111(1) in hoiling toluenc 1400 mt containing suffkicnt chlorntfllllc-thvlsilane to lowcr tbe reflux tcmperature t(l 102 . A total (lf 475 g (4:4 mol) nf chlorotrimethylsilanc is empillyedl, Thc reaction is vigoro\ls: when the n:action is wmpIete, the rea<.:tioll mixture i, di-luteJ wilh ethanol (10 dcstroy excess sodiulll), washcd with water and distilIed: yield: 600 g (87':<): h.p. 1)4.4'/23 torr: l1i;: t.~OI6: d~': O.Xi'40. '

Up to now examples 01' the formation 01' carbon-sili-con bonds via organozinc and -aluminum wm-pounds have only been reported with aliphatic wm­pounds. For the preparation of aryltrimethylsilanes the system of zilllc dust/chlorotrimethylsilane/hexa-methylphosphoric triamide otTers no advantages compared tü th,e procedures dcscribcd in SectillllS 2.3.1.. 2.3.2 .. and 2.3.3.1'1.

x Soln:r t

CI ether" or toluen.:

CI ether Cl tolucn,:" CI t(lluene" CI toluen,:" CI toluen,: Cl toluen.: Cl t\lluen,: CI toluen,: CI tolucne CI toluelll: Br toluelll: CI t:ther" ;lr

tolucm: Br tolucm: Br toluCI1l: Cl tolucm: CI toluene CI toluClle

CI tllluelll:

CI (oluen( CI toluene Cl t,lluene Cl toluene CI toillen( CI toluellt CI toluene

YieiJ ('Ji.] 01' 31

55 67

26 58 73 50 77 77 5877 52 85 2668 80

5065

SYNTHESIS

Reference

85,201"

81 152 152 152 61. 205 205 61, 142.206 61, 85,206 61.81. 206. 124 157 206 108", 202

121 121

84 207 74 82 208 59 1)4, 114

1)4 70 Wi 84 1)8 76

2(1)

210 85, 144 210 210 210,211 210,211 147

2.3.4. Prcparalions via Rearrangcrncnts

The silylation 01' organometallic compounds can also be achieved via rearrangements, i.e. without external silylating agents slch as chlorotrimethylsilane. Thus, the halophenoxytrimethylsilancs 32, after metalla~ tion with butylli:hium or magnesium to give 33, rearrange to the silylated phenolates 34, the hydroly-sis of which affords the phenols 35 21h 220 (Table 12).

32 33

34 35

No\cmbcr 1979 I'reparation nf Aryl- and Heteroaryltrimethylsilanes R53

Table 12. Trimethylsilyl-Substituted Phenols 35 via Rcarrangemcnt of Metallated Phenoxytrimethylsilancs 33 ._~--~-----

Sub,trate 32 R' R 2 R 1 X ----------------------- -- ._---------

II 11 2-Br H 11 2-Br

H H H 3-Br H H 4-Br H 11 4-BI" H 1I 4-BI"

H,C " 2-Br H,C H 4-Br

I-C4H., B 2-Br I-C411 .. 11 2-Br I-C4H., (-C4 11., 2-Br I-C,B" t-C,II., 2-Br Br [-C4 B" 2-BI" Br Br 2-Br Br Br 2-Br I-C4H., (1I,C),si 2-Br H (H,C),Si 2-Br H Br 2-Br I-C4 11., Br 2-Br H,C I-C4 H., 2-Br CI CI 2-Br I-C4 IL, Br 2-.1

" Yield determined by G.L.C./M.S. " Obtained as mixturc with other products.

Repeated application of this process to polyhalo-genated compounds 32 as well as the working up of34 with agents other than water provides further prepara-tive possibilities2tX •

Thio derivatives can undergo rcarrangement to give trimethylsilyl-substituted thiophenols in the same way161.97, however, the rearrangement of N-silylated haloanilines fails 147.2\(,. The rearrangement method can also be used with some pyridines 36 to yield tri-methylsilyl-2-pyridones 37 without diflicultiesl17

(Table 13).

1. f-C.HgLi 2. H20

)

36 37

Table 13. Trimethylsilyl-SlIbstituted 2-Pyridoncs" 37 via Rear-rangement of Pyridines 36 using I-BlItyllithilim '17

Suhstrate 36 R'

H H,C H H

R'

11 H 11 H (:.,H,

R'

H H H H,C

x

3-Br 5-Br 5-Br 5-Br 6-Br

Yicld Pi;1 nf37

62 51 98 47 69

a In the same way, 0- and N-trimethylsilylated pyrimidincs can bc rearranged to the C-silylated compollnds 2",_ 221.

-- ---_._-~----- -~-~."--~_._- --"~--

Metallating Yicld [";,1 RcfcrclIl'c agent 01'35

--------- -------_ ... __ ." --_ .. ,._-------- -~--"----------- -,

n-C4~LLi 2()-X6 97. 161. 216 t-C,IL,Li 100" 217 Mg SO 2U': I/-C4 IL,Li SO 97.216 I-C,I/.,Li 87" 217 Mg 17" 21X {-C,IL,lj 93 217 t-C,II.,1.i 80 217 n-C,H.,Li 96 21'1 Mg 80 218 II-C4H.,Li <)5 219.220 Mg 85 218 n-C41L,Li 85 219 n-C4 IL,Li 92 21<) Mg 25" 2111 Mg 70 218 Mg 84 218 Mg 6 218 Mg 83 218 n·C4 H,Li 90 220 n-C4 H.,Li 77 220 II-C41J.,Li 88 220

Another O~ emigration of the trimethylsilyl group was observed for 4-trimethylsilylcoumarin222

• The apparent N ~ emigration upon silylation of the pyr-role anion lXII is presently explained as a double sily-lation with subsequent solvolysis ofthe sensitive nitro-gen-silicon bond 1XI. The acid-catalyzed (trifluoro-al~etic acid) isomerization 01' 1,2-bis[trimethylsi-lyl]benzene to the 1,3-isomer, which occurs on heat-ing at 1500 for 48 h in a sealed tubem .224, is ex-plained by anormal (T-complex mechanism. Surpris-ingly the catalyst does not seem to be consumed by protodesilylation, as expected according to arecent paperS7

• Indeed the isomerization also proceeds us-ing 5 mol-'N; trimethylsilyl trifluoroacetate under the same conditions57

• lsomerizations of this type, also catalyzed by other agents, have been observed. but not thoroughly investigated 14'1.225.226.

3. Synthesis of Aryl- and Heteroaryltrimethylsilanes via Cycloaddition Reactions

Silylated aromatic and heteroaromatic compounds can be synthesized from appropriately substituted unsaturatedcompounds. Littleadvantage has been tak-en 01' the possibility 01' preparing aryl- and hetero-aryltrimethylsilanes in this way. lnteresting develop-ments should be expected, especially in the prepa-ration 01' silylated heterocydes.

854 1 }ieter Häbich, Franz EtTenberger

3.1. Aryltrimcthylsilallcs via [2 + 2 + 21Cycloaddition Rcac-tions

Cooligomerization of diynes 38 with acetylenes 39 in the presence of cobalt catalysts is a general synthesis for trimethylsilyl-substituted benzocyclobutenes. in-danes. tetralins 40, or naphthalenes 41 (Table 14).

r C::C- R' y '-C::C-H

38 39

Table 14, TrimethyLilyl-Substituteu Benzocydllalkancs 40 or Naphlhakncs 41 via 12 + 2 t 21 Cydoauuitil\n [{caclions

Di}nc ."ill Acetylene Prouuct Yidd [{cfl,r· [{' Y ."i9 type I"nl entc

R)

11 (C1L), (H,C"Si 40 !>o 226 (H,C),Si (CH,l, 11 40 12 227 11 (CII,) , (l1,C),si 40 51) 225 11 (CIU, (11 ,CLS. 40 ~9 225 H (CH,), fI,e 40 -'4 225 lf CII CIf, (lf,C),Si 41 30 22X

OSi(CII,), H CII eil) (I I ,C),Si 41 30 22x

OC/L 11 CII CH, (11 ,O,Si 41 30 22X

2-Thp' -_ .. _~-~".- -- --- -. ~-.----- - -----~._---------

" Thp = 2-tetrahydropyranyl.

The cyclotrimerization of trimethylsilylacetylenes in the presence of cobalt catalysts22'J or the system ti-tanium(IV) chloride/trimethylaluminum 21o is diffi-cult to direct and nonnally affords isomer mixtures of polysilylated henzenes.

3.2. Aryl- and IIctcroaryltrimethylsilancs vht 14 + 21Cy-c1oaddition R,eal'tions

Cycloaddition reactions 01' a-pyrone (42) or tetra-phenylcyclopentadienone (43) with trimethylsilyl-acetylenes 39 lead to aryltrimethylsilanes 44 (63%)2:11 or 45 (90%f32, respectively.

Very strained systems such as trimethylsilyl-substi-tuted benzocydobutenes and -hutadienes undngo

39

~o I~ö (42)

SY1-d HESI~

45 R' = H, R' : CsHs

ring-expansion l) n treatment with alkenes and al-kynes to afford letralins 226 and naphthalenes 174 of types otherwise n:)t readily obtainable. The addition of 39 [R 1 = H, Si(CH,hl tn 3,6-bis[ methoxycarbonyl] 1,2,4,5-tetrazine gives C-silylated pyridazines 00-R5~Y,) with elimination of nitrogen:"l.

3.J. Ilet('roaryltrimcthylsilanes "ia 12 + 3JCycloaddition Reactiol1s

The pyrazolyltrimethylsilanes 47-49 are readily ob-tained in good ydds by the cycloaddition of tri me-thylsilylalkynes 39 to diazomethane derivatives 46 (Table 15).

46 39

R3 Si(CH3b

R2i;) (H3ClJSi R3

2bN and/or R W"

~1 ~1

47 48 49

'fable 15. Trimethylsilyl-Substituteu Pyrazoles 4;-49 via [2 + 31Cy-c1oaddition Rea~tiolls

_.~_._._~---

I )iazomethane 46 Alkyne 39 Product Yiclu Refer-R' R' R' typ" 1~',1 eil<'<' - .--- ---~"'----- ---------- -~_ .. _-_.- ._-----_.- -~-- ._- --- ._---------_.------------

H 1\ 11 411 WO 23~, 235 11 11 C"Jl" 411 20 25 2.14. 236 Il 11 CII, 411 I 234 11 H ~HiC)\Si 48 60-95 234,236 H 11 HOCH, 411 40 234 H C1II,OOC :H,C)IS. 48 'i2 236 H C211,00C H 411 99 2Yi 1I H 0 CIl 47 t411 28+72 234 11 11 II,COOC 471411 20+ ~;o 234 11 Il ILC CO 471411 30+ 70 23) Il;e ",C Ii,COOC 49 WO 234

_."-~-----_._-- -~---~--- -" ----

In the ca se 01' ta .ltomerizable compounds (R· = H) the orientation 01' the addition proceeds with high re-

November 1979

gioselectivity to afford predominantly the pyrazoles 48. This is probably due more to steric than to elec-tronic factors 2J4

•

Using this method, trimethylsilyl groups can also be introduced via a [2 + 3]cycloaddition reaction as shown by the reaction of bis[trimethylsilyl]diazome-thane with acetylenedicarboxylic ester. One tri me-thylsilyl group migrates to the nitrogen atom, yield-ing the corresponding pyrazole (73%f37.

3-Pyrazolyltrimethylsilane (48; R '-R' = H)m: Trimethylsilylacetylenc (4.91 g, 50 mmol) and diazomcthane (70 mmol) in dry ether (100 ml) are kept in the dark !,)r 3 days at rl)onl temperature. After thc destruction 01' cxcess diazomethane by short boiling. filtration and rcmoval 01' thc solvent in vacuum a1'fords thc product: yicld: 7 g (lOO'){,); I1l.p. 79-RO' (pentane); b.p. 113 114/14 torr

Nitrile oxides 50 react regiospecifically with trime-thylsilylalkynes 39 to atTord the isoxazoles 51 21K

•

R2 R'

R'-C:::N70 + RLC:::C-Si(CH3h ---?> )j (H3ChSi o,..N

50 39 51

R1 R2 Yield [%]

a HJC (H1ChSi 46

b C,H, (H3 ChSi 44

C ',3,5-tri- H3C- CSH2 (H 3ChSi 98

d H3 C H 69

e CsHs H 62

',3,5-tri- H3C- CSH2 H 98

The triazolyltrimethylsilanes 53-55 are obtained in good yields via the addition of azides 52 to tri me-thylsilylalkynes 39239

•

e $ RLN-N:::N + R2-C:::C-Si(CH3l3 ----7

52 39

R2 )=(Si(CH 3l3 (H3C)3Si)=(R

2 R2WSi(CH3h

N~ .... N ..... , + N~ .... N ..... R'

+ N~ ~N N R 'N ....

I, R

53 54 55

R1 R 2 Yield (53) Yield (54) Yield (55) [%] [%] [%]

a (H 3ChSi (H3 CbSi 66

b (H3 C)3 Si CsHs 87

C CsHs (H3 ChSi 76

d CsHs CsHs 3 97

e CsHs COOCH 3 80

CsHs COOC 2Hs 65

Preparation 01' Aryl- and Heteroaryltrimethylsilanes 855

Triazoles of type 54 are also formed in low yields by the addition 01' trimethylsilyldiazomethane to car-bodiimides240

•

4. Introduction of Substituents into thc Nucleus of Aryl- and Heteroaryltrimethylsilanes

The often rigorous reaction conditions needed lor the direct introduction 01' trimethylsilyl groups into aromatic and heteroaromatic compounds (c.f. Sec-!.ion 2) require that various functional groups be in-troduced into the nucleus after silylation or subse-lJuently constructed by transformation of substi-tuents already present. Ideally, the trimethylsilyl group plays thereby the role of an inert substituent. With the introduction of electrophiles, the desilyla-ti on reactions' can dominate over the desired depro-tonation reactions, thus affording completely desily-latcd products. Desilylation is avoided by the use of organometaUic derivatives which are always more reactive towards electrophiles than the correspond-ing hydrogen compounds. In the case of the transfor-mation 01' substituents attached to the nucleus, reac-tion conditions have to be chosen to avoid cleavage of the trimethylsilyl groups.

4.1. H alogclla tioll

Halodesilylation reactions proceed extremely weIl; thus the ipso-rate factor is lOx for the bromination and 10<> for the chlorination 01' phenyltrimethylsi-lane'. Consequently, nuclear halogenation reactions without considerable halodesilylation are ooly possi-ble at strongly activated positions, for example in the p- and o-positions of m-trimethylsilyl-substituted anilines and phenols 56.

~ - HBr

56a-c

x Yield (57) [%]

a OH 83

b NHCOCH, '00 C N(CH3)2 86

A YSi(CH3l3

Sr

57 a-c

Br2 ~ - HBr

Referenee

241, 242

243, 244

245, 246

X .,* ~I Si(CH3b

Sr

58a, c

The partial halodesilylation 01' bis[trimethylsi-lyl]benzenes 59 to the corresponding halophenyltri-methylsilanes 60 is of broader applicability (Table 16).

856 Dieter Häbich. Franz Elfenberger

R,~H3h (H3C)3SiX/X2 >

R2VR4

R3

59 60

Table 16. Halophcnyltrimethylsilanes 60 via lIalodcsilylati(\n 01' Bis[trimethylsilylJbenlcne Derivatives 59

Suhstrate 59 Yicld Refcr-R' R' R' R4 X [""J enc~

(H,q,si 11 11 11 J 40 95 42.247" 11 (H,C) ,Si H H J X5 96 247" H H (~"ChSi H 82 97 247' (H,C),Si H 11 H Br [42 (H,C),Si (Clhh H Br 227 (H,C),Si H (CII,).' Br 226 (H,C),si H (CH ClI), Br Xl) 22X

" Also used were J 2 • .!Cl, and J Br.

3-Iodophenyltrimethylsilane247:

At ()" a solution (11' iüdine hromide ([ 1.4 g, 0.055 mol) in carhon te-trachloride (30 rnl) is added dropwise to a solution of 1.3-bisltrime-thylsilylJhenzene (t 1.1 g, 0.05 mol) in carbon tetrachloride (HO ml), the mixture is kept fi.lr I to 2 h without cooling. Bromotril1lcthylsi-lane and carbon tetrachloride are distilled on; tbe residuc is dis-solved in ether, washcd with 0.3 molar sodium thioslilfate solution (50 rnl). then witb water, and dried with sodilll1l sulfate. Disülla-tion affl)rds the prr<duct; yield: 11.5 g (RS'!{,); h.p. 146 150/30 torr.

Halogenated hetreroaryltrimethylsilanes are also ob-tainable in this way. 4,5-Bis[trimethylsilyl]-3-methyl-isoxazole undergoes selective bromodesilylation on treatment with bromine only at the 4-position (69%)23X. Examples tor the halogenation of trime-thylsilyl-substituted organometallic compounds, which, as expected, do not undergo halodesilylation, have also been described; i.e. the chlorination of 2-li-thio-5-trimethylsilylthiophene (45%f4k, as weil as the bromination (3391.) and iodination (67'Ji.) of 2-1i-thiophenyltrimethylsilane \2(,. In contrast to the reac-tions at the nuclleus, the direct halogenation of side chains proceeds in a free radical manner, thus pre-venting undesirable halodesilylation. Depending on the re action conditions, the bromination of the tolyl-trimethylsilanes 61 with N-bromosuccinimide (NBS)/dibenzoyl peroxide (DBPO) leads to the monobromomethylbenzenes 62 (59-66~~i.) or dibro-momethylbenzenes 63 (46_70%)24('.250.

NBSIDBPO)

61 62

NBS/DBPO -------7

63

SYNTHJiSJS

4.2. Introduction 01' Sulfur Functions

Aryltrimethylsilanes react with sulfur trioxide or tri-methylsilyl chlorosttlfonate with insertion of sulfur trioxide into the .:arbon-silicon bond to yield trime-thylsilyl esters of arenesulfonic acids251 , which can easily be hydrolyzed to the free sulfonic acids. For example, by partial sulfodesilylation ofthe bis[trime-thylsilyl]benzenes 64, sulfonic acids 66 can be pre-pa red via the isolable trimethylsilyl esters 65 (80-· 88%) 123,142 252.251.

64 a ortho

b meta

C para

SHCH3l3

~S02-0Si(CH3l3 65a-c

SHCH3h

~503H. H20

66a-c

The deactivating trimethylsilyloxysulfonyl group in 65 impedes a further electrophilic attack of sulfur tri-oxide at the secoud trimethylsilyl group.

4-ITrirnethylsilyllbenl(~neslllfol\ic Acid Monohydrate (66e)"': A solution 01' sulfur trioxide (4.0 g, 0.05 mol) in carbon tetrachlo-ride (40 ml) is added dropwise, with exdllsion of'Il10istllre, to a stir-red solution 01' 64e (17 g, 0.077 mol) in (arbon tctracbloridc (70 ml) cooled wilh iee/water The mixture is heated IInder reflux for 1 ~ ruin and then fradionally distilled 10 givc 64e; yield: 5.1 g \30"(,); b.p. 7<)/2 torr and trimcthylsilyl 4-(tril1lcthylsilyl)benzeneslilfon-ate (65e); yield: 12.1 ~ (XO% based 011 64e cOl1slIrned); b.p. 150 151 '/2 torr; m.p. 83~6°. Clll11pOlind 65e is dissolvcd in water (15 ml) and after 15 min, water ami hexamethyldisiloxane are evapo-ratcd and the residuc recrystalli7.cd from bcnzcIlc to give 66.:: yield: 2.1 g (R5'X,); 1Il.p. X9 90°.

Trimethylsilyl-suhstituted diarylsulfones are pre .. pared by either partial sulfonyldesilylation of bis[tri-methylsilyl]aromatic compounds 67a-c using sulfo-

67 a-e

a 1H3ChSi

b (H 3ChSi c 4-IH 3Cl 3Si-CsH,--d CH,

e H

68

IH,Cl,Si

(H3Cj,Si (H 3Cl,Si

H

H

R '-Q-S02-Q-R3 69a-4i!

-----R' Yiel,j

['IoJ H 48 CH, 54 H 63 IH 3Cl 3Si 76

IH,Cl 3Si 87

November 1979

nyl chlorides 68 or by sulfonylation of unsilylated aromatic compounds 67d, e with trimethylsilyl-sub-stituted sulfonyl chlorides 68 [R3 = Si(CH1 hF54

•

Trimethylsilyl-substituted thiophenols (~50%) are formed when the corresponding Grignard or li-thium compounds are allowed to react with elemen-tal sulfur255,256 or with diallyl sulfideH5 •

4.3. Introduction of Nitrogen Functions

A number of arenediazonium salts 70 react with de-rivatives of aniline and phenol 71 (R 4 = NR 2• OH) carrying trimethylsilyl groups in the meta-position, to afford the azo compounds 72 (Table 17).

70 71

R'

~ R2-QN:N-p-R4

R3 Si(CH 3b

72

Table 17. Trimethylsilyl-Substituted Azo Compounds 72 via Cou-pling of Diazonium Salts 70 with Aryltrimethylsilanes 71

R'

H CI CI CF, SO,CH, SO,CH, H H NO, CI CI NO, CF, SO,CH, SO,UI, Oll H H COOH H 11

R'

NO, NO, NO, NO, NO, SO,CH, H NO, NO, NO, NO, NO, NO, NO, S02CH, NO, SO,H S02NH, H COOB SO,B

R' R4

H H CI H H B H H H H CI CI H H H Jl H H H 11 If

N(CH2CH20H)2 N(CB,CH,OH)2 N(ClhCH,OHh N(CH2CH20H), N(CH,CH20Hh N(CH,CH,OH), N(CH,j, N(CH,h N(CH,h N(CH,j, N(CH,h N(CH,), N(CH,h N(CH,), N(CH,h N(CH,h N(CH,h N(CH,j, N(CH,), N(CH,h OB

Yield Refer-[%1 ence

50 160 60 160 60 160 50 160 52 160 34 160 60 143,245 95 143, 245 36 143 77 143 66 143 35 143 R3 143 69 143 51 143 14 143 X7 143 75 143 53 143 65 143"

257 ------------------- ---~------------

a Includes azo derivatives of 2-naphthol.

As expected, p-trimethylsilyl-substituted anilines or phenols undergo diazodesilylation 143. In contrast, 2-dimethylaminophenyltrimethylsilane does not react with diazonium salts due to steric hindrance 143. However, 2-trimethylsilylphenol couples in the 4-po-sition258 . 2- or 4-trimethylsilyl-substituted azo com-

Preparation of Aryl- and Heteroaryltrimethylsilanes 857

pounds can be obtained without desilylation occur-ring if the trimethylsilyl group is located on the di-azonium component 70259. A nitrosation of aryltri-methylsilanes while maintaining the carbon-silicon bond intact is also possible, but only with strongly ac ti va ted anilines245 or phenols257 of type 56.

56 a x = OH

C X = NICH3)2

1. NaN02 2. HzO/H$

)

x

~ YSi(CH3b NO 73 a, C

The nitroso group has to be introduced by nitroso-destannylation reactions into less activated aryltri-methylsilanes, for example, to produce 3- or 4-ni-trosophenyltrimethylsilane (50%)260. Selective ni-trosodesilylation reactions were carried out with 3,4-bis[trimethylsilyl)pyrazole (74) leading to 75 (39-nW,) or 76 (36%)261.

(H3C13Si Si(CH3)3

HN ~N) H

74 j-CsHgONO

76

Sulfuric acid/nitric acid mixtures cannot be used for the nitration of aryltrimethylsilanes because of the ease of protodesilylation. In weakly acidic medium, phenyltrimethylsilane reacts with nitrating agents such as nitric acid/acetic anhydride, cop per nitrate/ acetic anhydride, or others 102.262 265 predominantly maintaining the carbon-silicon bond intact to form a mixture of 0-, m-, and p-nitrophenyltrimethylsilanes. The somewhat favoured formation of the m-product is a basis for conclusions about the directive effect of the trimethylsilyl group26(,. For the specific prepara-tion of certain isomers it is more convenient to apply partial nitrodesilylation of the corresponding bis[tri-methylsilyl)benzenes 64 using nitric acid in acetic anhydride [0 (90%)142, m (69?1l)X5,265, p (82%f67J. In contrast to earlier presumptions6,2X these reactions do not seem to be explosiveM.

2-Nitrophenyltrimethylsilane '42: A solution 01" nitric acid (70%; 6.3 g, 0.07 mol) in acelic an hydride (30 g) is added slowly 10 a solution of l,2-bis[trimcthylsilyl]bcnzene (4.5 g, 0.02 mol) in acetic acid. The mixture is kepl at 100' for 6 h, then cooled, and added 10 0.4 molar aqueous sodium hydroxide so-lution (400 ml)_ Ether extraction, followed by washing, drying with sodium sulfate, and fractionation gives the product; yield: 3.5 g (90%); b.p_ 98' /23 torr; n;;: L5271.

858 Diet,er lliibich, Franz Effenherger

Depending on substituenls X, p-subslituted aryltri-methylsilanes 77 undergo nitrodesilylalion to form 78 or normal nitration to form 79a.

x X X

Q nitration --~ Q + <t02

~I

Si(CH3b N02 SiICH3l3

77 78 79a

X Yield (78) Yiel.d (79) Refer· [%] [%] ence

------- -------NHCaCH3 29 51 269 OCOCH, 80 270 aCHl 82 6

CH) 55 263 F 67 72 >' 16 78 Cl 271

Xl Xl

(} nitration ~ )

~ SiICH3)3 ~ SiICH 313 NOz 79b

XZ qSHCH3)3 ~I

X' : aCH)

SilCH3h

X2

&SiICH3)3 X' = F

~I

x2

qSHCH3l; ~I

N02

79c

° IH3ChSi-Q-g-N3

80

81

SYNTllrSIS

Reactions 01' the m-isomers lead to the products of normal nitration 79b lXI"" N(CHd~ (40'?i,f45 , aCH: (81%t, F (65%)7N. Cl (80;){,)271). 3-Trimethylsilylacet-anilide is predom mantly nitrated ortho to the acetyl-· amino group (70;),»24:1.

The preparatioll of the silanes 79c [XC =cc aCH, (74% )207, F (19~X» 7Xj results from nitrodesilylation 01'

nitration, respeetively. The nitrati,m 01' 3-trimethyl-silylpyrazolc am) ,ds 4-nitro-3-trimethylsilylpyrazole (94%)235. The introduetion of amino groups into the aromatic nucleus is usually done in a nucleophilie manner or via reurangement reaelions. Thus, in the reaetion of 4-hromophenyltrimethylsilane with li-· thium dimcthylamide in ether· via the aryne inter-mediate-- 3-dimc:thylaminophenyltrimethylsilane is the main product (56%)145.

The applieation of rearrangement reaetions to intro-duee amino and funetionalized amino groups into the nucleus 01' aryl- and heteroaryltrimethylsilane~ ean be examplified by the Hofmann-rearrangement 01' 3-trimethylsilylbenzamide 14t and 3-trimethylsilyl-isonicotinie acid amide I >4 to give the amines, the Curtius rearrangement of 4-trimethylsilylbenzoyl azide 80 to give the isocyanate 81 272, as weIl as the Beckmann reaction 01' the 4-trimethylsilylaeetophe-none oxime with phosphorus pentaehloride or thio-nyl chloride to give the corresponding aeetanilide (87% )27.1.

The reaction 01' 81 with water. after elimination of carbon diox.ide, a11ol'ds the amine 82. Reactioll 01' 81 with anilines affords the diarylureas 83 [X= H. 2-CH" 2-0CH" 4-aC2H), 2-CI, 4-CI, 2,4-di-CI, 4-(CH lhSij and with alcohols, urethanes 84 (R = CH1,

C1H'i, 1l-C,Ih, ll-C4 H", C,H I h Cr,H), ChH,CH2) are förmed 272•

COlupound 81 diminates earhon dioxide when heated (5 h, 130-150") in the presence 01' 5-methyl-SH-dibenzophosphole and gives the carhodiimide (84"i;)274. The sulfönamide 85 ean be rearranged us-

ROH

IH3C13Si-Q-NH2

82

° IH3C)3 Si-Q-NH-g-I\lH-Q

X 83

84

November t 979 Preparation of Aryl- and Heteroaryltrimethylsilanes 859

ing butyllithium via the anion 86 to yield 87 (93%) with c1eavage of sulfur dioxide m,.

n (H3C)3Si S SOz-N(CH3}z

85

86

N(CH3)Z

Jj (H3ChSi S

87

4.4. Introducdon 01 Pbospborus Jt·unction. ..

In order to introduce phosphorus substituents into aryltrimethylsilanes, it is necessary to use organometal-lic compounds, because otherwise phosphodesilyl-ation27S occurs under the conditions of electrophilic phosphorylation (Table 18).

4.5. Alkylation and Hydroxyalkylation

Since aryltrimethylsilanes undergo alkyldesilyla-tion3•279 under Friedel-Crafts conditions only, the partial alkyldesilylation of poly[trimethylsilyl]ben-zenes can lead to the desired compounds. In this manner the reaction of t,2-bis[trimethylsilyl]benzene (64a) with I-butyl chloride/aluminum trichloride gives 2-t-butylphenyltrimethylsilane 142. Again, al-kyldesilylation can be avoided by the use of the cor-responding organometallic compounds 88. By reac-tion with alkylating agents R X, an access to var-ious alkylated compounds 89 is provided (Table t9).

n (H3ChSi~yJ-..M

R-X ~

88

The biologically active thiophene derivative 90 is ob-tained by alkylation of the 2-lithio-5-trimethylsilyl-thiophene with oxirane and subsequent phosphoryla-tion (51%)179.

'fable 18. Phosphorus-Substituted Aryl- and Heteroaryltrimethylsilanes via Trimethylsilyl-Substituted Or-ganometallic Compounds

Substrate Phosphorylating Agent Pruduct Yield [%1 Reterence .. *.- -~ .. _._ ... _*._._ ..... *--

~H1ChSi-{) 1p 35 276

pels ~HiC)jSi{)-lP 45 2'76

~HlChSi-C}l /'.'0 30 2713

50 277

60 277

58 218

58 278

56 1'19

46 179

66 179

31 179 _ .... _--_ .... -----_ ... _---

S60 Dietl:r Häbich, Franz EtTenberger

Table 19. Alkylation of Aryl- and /Ictcroaryltrimctbvlsilane, via Organomdallic Derivatives 88

Substrate SS Y M

-CH=CH- Mg8r

-CH=CH- MgBr

-CH=CH- Li

5 Li

5 Li

5 Li

1.,&

R X

Cl);.. , N N ')-Cl

clN

F1C=CF-F

O:~H 0

D

90

Yidd [%]

15

32

50

29

Rl'Icr-ene.:

280

281

282

283

175

2/.8

Alkyne-substituted aryltrimethylsilanes 93 can be prepared by coupling reactions of 91 with acetylenes 922X4

, as weH as by addition of trimethylsilylalkynes 39 to benzyne 11,1,

91 92

Cu/pyridine -0" 1 ---7) (H3CbSi _ \ C:C-R

SYNTHESIS

Alkylation of he ~eroaryltrimethylsilanes containing nitrogen-hydrogen bonds leads to the N-alkylated derivatives214 and from compounds 94, salts 95 are obtained IX2.IX4.

94

) ():>-Si(CH3h I Gl xe CH3

95a Y : 5, x" 0502F 187%) 95 b Y : NCH 3 , X : J 191 %)

2-Pyridyltrimeth)lsilane was also eonverted into the eorresponding quaternary iodide (':11 ~\,)~I,

The free radieal arylation of phenyltrimethylsilane induced by dibenlOyl peroxide gives a mixture ofthe isomerie trimethylsilyldiphenyls (overall yield 2()'J6fx5

, Hydrox:ralkylation of aryltrimethylsilanes with aldehydes in the presence of aluminum triehlo-ride always lead~; to mixtures of isomers286

, Orga-nometallic derivatives 96, however, reaet with alde-hydes and ketones speeifically to give the corre--sponding alcohol ~ 97 (Table 20),

96

)

97

Tahle 20. Benzyl AIcJhois 97 via Rcactions PI' Grignard C011l-pounds 96 with Aldehydes or Ketones

Yicld Rcfcrcncc [%]

9H1 9HJ

93 a R1 : -C-O-CH-OC,H". 185'10) CH, I H 33 50 65, 169. 2XI, 2g7, 2~8 CH 2 --CI eH, eil, 42 49 2~1, 2XX, 289, 290

F OBr ~7 [0]

93 b R2 : N(C 1Hsh i21 '/0)

93 C R2 : NICH 3 l1C sH5) 116'10)

Pentafluorophcnyltrirm:thylsilane can be alkylatcd with n-butyllithium in the 4-position as the result of direct nucleophilic attack 19~.

C"II, " 20 52 65,212

Analogous reaeti Jns 01' 2-lithio-5-trimethylsilylthio-phene with benz.lldehyde (yield: 30W,f91 as weIl as o[ the 5,8-dilithin adduet of 1-naphthyltrimethylsi-lane with aliphatie aldehydes CH3(CH2)nCHO (n=O, 1, 2. 3; yields: 37~46%fi9 have: been de-scribed.

4.6. Acylation

Normal acylatioll competes with acyldesilylation in tbe Friedel-Crafls aeylation of aryltrimethylsilanes, Thus, acyldesilylation of phenyltrimethylsilane (98)

November 1979

with acetyl chloride/aluminum trichloride is greatly favoured over the normal C- H acylation by an ipso-rate factor3.279 of 10'-104.

With acyl fluorides/boron trifluoride, however, both reaction pathways seem to take place at a eompara-ble rate yielding a mixture of 99 andtOO('-' ")~

98

o 11 /

R-C-F/BF 3 )

o 11

~ 1 + a C- R

~

99

{jrSi(CH3l3 :/1

R-C ~ 11 o

100a R = CH 3

b R = C6H5

Normal acylation is favoured when strong substi-tuent effects counteract the ipso-directive elreet of the trimethylsilyl group. Thus, 2- and 3-methoxy-phenyltrimethylsilane are always acylated para to the methoxy group5 I,2Sg, 163 and do not undergo acyl-desilylation as was earlier reported279• The relations with 3-thienyltrimethylsilane (101) are similar. Com-pound 101 exclusively reacts at the position that 1'a-vours an electrophilic attack to yield .02 (R = CH" Cc,H5; using tin (IV) chloride titanium(IV) chloride, aluminum chloride as catalysts; yield: 14-52%?1. The mineral acid emerging 1'rom normal acylation, in the presence 01' the catalyst causes protodesilyl-ation 01' still unreacted 101 1'orming thiophene, which is subsequently acylated to yield 103 (24-59'1(,). This side reaction has not been seriously laken into account in most of the earlier investigations.

/j"\('S i(C H313 t,; 5

o 11 / R-C-Cl catalyst

)

101

+ n R-C.....((s)l

11 o 102 103

The acylations of 2-thienyltrimethylsilane [acetyl chloride/titanium(IV) chloride (42%)'1, acetic anhy-dride/iodine (13%)293, benzoyl chloride (17%)2'14],2_ furyltrimethylsilane [acetic anhydride/iodine (25W»29J], and N-methyl-2-pyrrolyltrimethylsilane [phthalic anhydride (55%)294] lead to the 5-acyl-2-tri-methylsilyl compounds. The only moderate yields indicate that side reactions, involving acid 1'ormed by acylation, also take place in these cases. The partial desilylation of poly[trimethylsilyl]aromatic com-pounds provides a convenient way to prepare acyl-phenyltrimethylsilanes. Since the reactivity 01' the

I'reparation 01' Aryl- and Heteroaryltrimethylsilanes R61

mono-acylated compounds is significantly reduced no further reaction takes place 142.

2-Acetylphenyltrimethylsilane' 42;

Acetyl chloride (2,3 g. 0.03 mol) in carbon disulfidc (15 1111) is ad-ded to a stirrcd. icc-wolcd suspension 01' aluminum chloride (4.0 g) in carbon disultidc (:i0 ml) containing 1,2-bisltrimcthylsily1Ihcn-zene (6.ti g, (J,(J3 mol). Thc mixture is heated under rcllux I(lr I h. most of the solvent is distillcd oll, and the residue is addcd to ice/ water (!OO 1111). Bcnzene extraction f(lllowcd by washing. drying with sodium ,ulfatc, and fractionation givcs the pmduct: yicld: 2.8 g (50%); b.p. 88/3 torr; ni; 1.5181.

The unwanted side-reaction, acyldesilylation, in the preparation 01' acylaryl- and -heteroary ltrimethyl-silanes can be completely avoided by using the reac-tive organometallic derivatives 104. In this case, in ad-dition to the usual acylating agents (i.e. acyl halides or anhydrides), which direct1y affords ketones 106 (route a), nitriles also can be used. Primarily, the imino deri-vatives 105 are formed (route b), which after. hydroly-sis give the ketones 106 (Table 21).

0 0 11 R-C-X fI

(H3CbSi-Ar-C-R

a 106

(H3C13Si-Ar-M i H2olH'1l 104 b

NH R-C::::N fI

(H3CbSi-Ar-C-R

105

To obtaill acylphenyltrimethylsilanes 109, the tri me-thylsilyl group can also be introduced by the acylat-ing agentt07, generally involving Friedel-Crafts ca-talysts (Table 22).

107 a ortho

b meta

C para

108

109

Trimethylsilyl-substituted alkyl aryl ketones are ob-tained by addition 01' aliphatic Grignard compounds RMgX (R = CH), C2Hs, C6H I" Cr,H"CH2) to 4-cy-anophenyltrimethylsilane 296

•

The formylation of aromatic compounds is a special acylation reaction. Reactive aryltrimethylsilanes un-dergo direct 1'ormylation according to Reimer-Tie-manu 257 ,270,2<;X as weil as Vilsmeier245 • In general. tri-

862 Dieter Häbich, Franz EtTenberger SYNTHEsrs

Table 21. At:ylaryl- and Acylhctcroaryltrimcthylsilanes 106 via At,,.ylation of Organornetallic Cornpounds 104

-------_._*" -.-_._-_._.-.~._._.---- -._. _ .. ,-- ...... __ ._ .... - .' ... _._ .... _ .. _ .... ~_ ... _-----_ .... _-----Sub!ltrate 104 Routc Acylating agent Proouct type Yieldl%1 Rcterences -_.,. __ . __ .----. • ••••• _-~_.-~. __ ._.~ •• - .* •• _-- •• _-_ .. . ·~~· __ · __ ·_·"~~_H_._ . ___ ... __ ._*~. ___ . __ .~. IH:.ChSb-

'_' MgElr b H:iC'{)-CN 106 82 16A

(H~C)3Si-{)-M9Br b H3C-{}-CN 106 64 166

(HlC};Si-o" MgBr b H3CO-{)-CN 106 33 168

(H3C}'Si~Li '- ~" b Cl·O-CN 105 75 248

Cl (H,C)3SitrLi b C}CN 105 51 248

(H3Cl3Si~Li \ I. b H,COCN 105 54 248

iH,C),SitrLi b tJ-CN 105 30 248

(H:iCh Si_i.jrLi b N~ct~ 105 SB 248

0 0 IHJCl,Si-{}MgBr " ~II II-f~ t: -c-·o-c I:::,> 106 (R: f}) 33 295

0 0 IH lChSi-f:}M9B r

11 11 106 IR : H3C) a Hj C-C-O-'C-CH3 39 29:

0 (>

!H,Cl,Si-{j-Mger 11 11

106 IR • ClHS) a C2H5 ""C-'O-C-C?H; 44 295

0 0 IH iC)3 Si-(}MgSr

11 11 106 IR = n-ClH,) a n-CJH7""C" 0""C-,C311 1-1) 31 295

tH3ChSi 0 H3CO~CdC! 11

106 IR • H,Cl a HJC- C-,Cl 41 20'/

-----------~--------_ .. ,- ._._--~------_ .. _ .. _-_. -_._-_ ... _---------

'fable 22. Bcnzoylaryltrirncthylsilanest09 via Benzoylation with Trirnethylsilyl-Substitutcd Benzoyl Chlorides i07"

,,------~ --._-_. __ ._----_._._------- ._ ... __ .-Rea<..1ants Cata- R in Yic\d Rcler· t07 tOll Iyst 109 I ~\ll enel!

.. _--_.---_. __ .. _ ..

a H3 co-Q-Cdsr 4-H]CO 168

a H3c-Q-Cdsr 4-H3C 168

c H3C-Ü AICI] 4-H]C 66 168

c H3CO-Q SnCI2 4-H3CO 80 168

b H3C-o AICl] 4-H]C 43 168

0 0 II-Q-

It 279 c CI-C '_' SUCH]), AlCI] 4-Cl-C- 33

c H3Cb-

'_" SilCH3h AlCI] 3-H]C '0 279

b IH3ChSi-{j-SilCH]h AICI, 4-IH JCl3Si 75 279 ._-,-,--_._----_ ... _----- "'-' . '-

• 2-Thienyltrimethylsilane was also acylated with 1e7c in this way (32%)m.

methylsilyl-substituted aromatic Grignard com-pounds can be collverted to silylated aromatic alde-hydes by use of fhrrnic acid orthoesters62•297, dime-thylformamide 175, or tbrrnic esters2911•

The direct introdt:ction of cyano groups into aryltri-methyl<>ilanes is rather difficult to achieve. The use of cyanogen chlor:de/aluminum trichloride predom-inantly results in desilylation2"" and use of copper(I) cyanide and aryl bromides provides low yields (12%) even when vigorous conditions are applied296•

Therefore the elimination of water from a<..-yl amides nsing phosphoryl chloride is the preferred method (86%)204 to obtain cyanophenyltrimethylsilanes.

4.7. Carboxylatlon

The carboxylatior. of aryl- and heteroaryltrimethyl-silanes is almost exc1usively achieved by reaction of organometallic compound<> 104 with carbon dioxide (Table 23).

(H3ChSi-Ar-M

104

t. C02 2. H.O/H$ --~) (H3ChSi-Ar-COOH

110

Novembcr 1979 Preparation of Aryl- and HetcroaryltrimethyL'Iilanes 863

Table 23. Trimethylsilyl-Substituted Aromatic and Heteroaromatic Carboxylic Acids 110 via Carboxylation or Organomctallic Cllm(lounds 104

Substrate Yield Refcrcnce Substrate Yield Reference 104 (~V,J 104 (%1

. -~-"'---'-'*~---'" ... _. __ .... -.......

)ilCH3h (H'CI'~ (\ -Li 60 142, 168 F I' '\ Li 171

!HlCllSb-CI F •

1'_'\ -Li 48 85, 9~1, 144 IH,CI,Si-ü'Li 62 293

(H)CljSi-Q-Li 38- 66 99, lö8, 300

(HlCl.lSi (H,CI,Si~Li 62" 293

H1CO{)-U 207

{H3C)lSi-{J-{~}U IH,CI,Si~Li 48 301

40 lS? CI CI

(H3C)lSi~

"-5-::.\ Li 171 IH,CI,Sifr.SOz-NlCH3Iz 10 176 F F H Li -_._-_ .. _--_._----.- . __ . .. "-"---"'-' -.. ----_._.- . __ ... . , .. _--_ .. _- .

• Treatment with cthyl chloroformate anords the corresponding lumn carboxylic estcr (59%):«'2.

'l'able 24. Silylation or Organometallic Derivatives or Aryl- and Heteroary1trimethyl~ilanes - ._-----~----~._-_._----_ .... _.--------_. __ ._----- -._._ .. _._---_ .. _ ... _-- .... ,-_._---_. Organomctallic Derivative Silylating Agent Pnlduct Yield (\~'J Rdcrencc -_ .. _-------_.~--_._--_.~-_._-------~ ... - ~ .. - ._._._---_. ~ .. _. ---_._. . .... _ .. _--- ---

CH! CH] IH,ChSi_Q_M9CI CI_Q_~i-Cl IH1ChSi_Q_~i_Q_CI 52 303"

- I CH, CH,

CH3 IH,ChSi_Q_M9Br H3C-SilOC2HSh IH3CI3Si_Q_~i-OC1H5 57 252

- I OCzHs

IH3ChSi_Q_U CsHs

ICsHshSiCI2 IH3CI3Si-Q-~i_Q_SilCH,I, 86 140 - I -

C6HS

IH'CJ,Si_Q_U SiCI, ~H3Cl,Si_Q_l Si 77 140

CH3 IH,Cl,Si_Q_Li IH,Cl2SiCI2 IH3CI3Si_Q_~i_Q_SiICH,I, 41 167

- I -CH,

CI CI CH, CH, IH,ChSI_Q_U

I I IH3CI,Si_Q_Ji-O-Ji_Q_SiICH,I3 IH,CI2S/-Q-SIICH,12 20 167

- I I-cH, CH,

IH,chSi~Li 'fHs i H3

CeHs-Si-CI IH3ChSi-o-~i-C6Hs 30 291 ~ A I

CH, CH,

i H3 erH, IH,CI,Si1)--~i-CH2Li IH,C),SiCI (H3CI,Si~Si-CH2-SiICH,1, 17 291

~ ~ I CH, CH,

rH3 iH, rH, TH, IH,ChSi~~i-CH2li CsHs-~I-C( (HlChSi~SI-CHcSi-C6Hs 17 291

~ A I I CH, CH, CH, CH,

1H3C1,So.- IH3ClsSi 1'_'\ CI Na/F-SilCsHsh O-SilCeHsh 75 252

" Fuether trimetbylsilyl-substituted oligomen; are liMcd bere.

864 Dieler Häbich, Franz EtTenbergcr

4.8. Silylation

The stability 01' carbon-silicon bonds towards orga-nometallic compounds makes it possible to introduce further silyl groups into aryl- and heteroaryltrime-thylsilanes. The hereby applied methods are not dif-ferent from those used to introduce the first trime-thylsilyl group (d'. Section 2.3.) (Table 24).

4.9. Protonation

Protonation of aryl- and heteroaryltrimethylsilanes leads to the formation of salts, protodesilylation. or replacement of other substituents by hydrogen, ac-cording to the substrate and the reaction COlH.li-tions.

Basic heteroaryltrimethylsilanes 11f or 94 react with acids to form salts 112 01' 113.

Ü .. H-X ) R N Si(CH3h

111

R = H; X = Cl, Hr .. L BF/' R = 11, Br, Si(CH ,h: X ~ (icCh ",

94

Y =S: X=Cl. 1"4 Y=NCIl,: X=Cl"" y = S: X = (JeU3 1114

112

~Y}-Si(CH3l3 ~N$

~ Xe

113

3,4-Bis[trimethylsilyl]pyrazole (114; R ,= H) can be converted quantitatively into its nitrate or hydro-chloride by treatment with concentrated acids105

.

However, in sulfuric acid/ice, protodesilylation oc-CUfS. Thus, the trimethylsilyl group of 114 (R oe= H, COOC2 Hs) can selectively be removed from position 3- or 4-, according to the reaction conditions215 .

Si(CH 313

RJ[) I H

115 (100%)

114

4.5-Bis[trimethylsilyl]-3-methylisoxazole behaves analogouslym. 3,5-Bis[trimethylsilyl]-I-methylimid-

azole is smoothly hydrolyzed in a water/dichloro-methane mixture to give 1-methyl-5-(trimethylsilyl)-imidazole (90%) 1:';. Halide substituents in aryltrime-thylsilanes H7 caH he replaced hy hydrogen via the organometallic intermediate without reaction occur-ring at the trimethylsilyl group 171.

:*":" F 117

1. n-C4HgLi 2. H20 -~

SHCH3b FrJ-pF XYH

F

118a x = F (75%)

b X = CI (75 %)

5. Transformation of Substituents in Aryl- alld Hcteroaryltrim'~thylsilanes

Aside from the substitution reactions at the nucleus 01' aryl- and helerüaryltrimethylsilanes, the transfor-mation and functionalization of substituents, at-tached to the silylated ring, is an important method for the preparation of some aryltrimethylsilanes. Hereby, it is im pOl ta nt to choosc reaction conditions that do not permit desilylation reactions.

5.1. NucleophiIic Ex<:hange or Halides

Benzyl hromides 62, readily available by radical ha-logenation 01' tolyltrimethylsilanes (cf. Seetion 4.1.), easily react with r ucleophiles (X) with su bstitution 01' bromide.

62 a ortho

b meta

C para

119 a-c

Thus, alcohols 1191: (X=OH?{J(, are formed with hy-droxide ions as weIl as ethers 119c (X = OCH 3,

OC2H" OC,I-lsf'06 with alcoholates, and esters t19a-c (X = OCO(,H~?511 with carboxylates. The in-tramolecular subst ttution of chlorohydrins leads to oxiranes2x4. With sJdium hydrogen sulfide .. thiophe-nols 119c (X = SH)306 and with sodium methylmer-captide, thioethers 119c (X = SCH1)3ilo are ohtained. Amino groups [X",NHCH3 , N(CHJh] can be intro-duced hy using amines or lithium amides 10".m. Di-et hy I (trimeth y lsi lyl)-phenylmet hanephosphonates 119b, c [X = P(O)(OC21·:U2] arise from the reaction of 62b, c with sodilm diethyl phosphite227 .

Cyanomethylphen~,ltrimethylsilanesf 19 (X = CN). important for further conversions, can he pre-pared in good yie Ids by reacting 62 with cyanide ionsJ0630X. Trimethylsilyl-substituted phenylacetic acids, obtained by saponification of nitriks 119a-c

No\~mbcr 1979 Preparation of Aryl- and Heteroaryltrimethylsilanes 865

(X = CN) in yields of SO_90%106.307, afford the me-thyl esters when treated with diazomethaneJ(j(,. The corresponding amide is obtained in 83"h yield 163 from the reaction of N,N-diethyl[2-trimethylsilyl-phenylethynyl]amine with hydrogen chloride/ether.

The acidic n-C H bond of 4-cyanomethylphenyl-trimethylsilane 119c (X = CN) can be methylated with sodium amide/methyl iodide (80W,) or acylated with sodium ethoxide/ethyl acetate:l07. Salts of C H acidic compounds 120 have been used as C-nudeophiles to afford compounds 121.lox .

62c

H I

eC-R1

~2

120

H

--7 (H3CbSi~CHz-t-R1 "=T I RZ

121 a R' : R' : COOC ,H, (22%)

b R' : COCH3, R' : COOC,H5 (17 %)

The conversion of the benzyl bromide 62c to the Grignard derivative 119c (X = MgBr) and subse-quent treatment with sulfuryl chloride leads to the sulfonyl chloride 119c (X = S02Cl) 109.

Substitution reactions on 4-[ß-chloroethyl]-3fl7 as weU as 4-[3,5-dichlorotriazinyl]phenyltrimethylsi-lane2xo with amines have also been described.

As expected the dibromomethylbenzenes 63 can be hydrolyzed to give the benzaldehydes 122 (49-69'),;) 101,1 (,9. 249. 2:;O.} 10.

(H3C13Si-o-CN

126

5.2. Functionalization of Carboxylic Acid Derivatives

Trimethylsilyl-substituted benzoic acids 123. easily obtainable by carboxylation reactions (cf. Section 4.7.), afford the acyl chlorides 124 when treated with thionyl chloride 16X,172. 30X, 311. The conversion of acyl ehlorides 124 to the corresponding acyl amides 125 can be effected easily with ammonia or am-line62. 144, 16X,.10X.

Si(CH3b

G-COOH

123 a ortho

b meta

C para

124 a-c

125a-c R : H, C6H5

Acyl chlorides, obtained in a similar maIlller from 3-and 4-trimethylsilylphthalic acid, form esters on reaction with methanop12 and with ammonia give aeyl amides]04,312.

The methyl esters of 4-trimethylsilylbenzoic acid x'. 4-trimethylsilylphenylacetie acid '06, and 4,4' -trime-thylsilyldiphenylcarboxylie acid 1 <;7 can be prepared directly from the acids by using diazomethane. An-other pathway to aequire derivatives of 4-trimethyl-silylbenzoic acids starts [rom 4-cyanophenyltrime-thylsilane (26), whieh aceording to the reaction conditions, can be converted to the amide 127 or the iminoester hydrochloride 128. This permits the pre-paration of the ester 129 or the amidine 1302<"',

o (H3CbSi-o-g- NHz

127

o (H3ChSi-o-g-OC2Hs

NH· HCI

(H3ChSi-o-g-OC2Hs 129

63 122 aar/ho

b meta

C para

128

130

Amino-imino-isoindolenines 132 (90-92'}(,) are ob-tained from phthalic dinitriles Hf 204.

131

NaNH21 H-CO-NH2)

132

R66 Dieter Häbich, Franz EtTenberger

53, Functionalizati.on of Hydroxy and Amino Groups

Hydroxy compounds most important in this connec-tion are the phenols, although alcohols like 4-trime-thylsilylbenzyl- or -phenylethyl alcohol can also be converted into the corresponding chloro3117,30

ll or acetyl compounds 169,250, respectively, Trimethylsilyl-phenols and -thiophenols 133 react with various electrophiles to afford the 0- or S-substituted deri-vativest34, wh ich, in many cases, are used only to protect the functional group212,250.

133 a-g

Y E

E-X --? - H-X

X

134 a-g

Yield Referenee

[%]

a 0 S02-CsHcCH3-P CI 73 126 b 0 CH 3 OS03CH3 257

CI 87 64 OS03CH 3 85

Cl 75-90 255

H3C- CO- O-CO-CH3 90 257,270

Acetylene reacts with 4-trimethylsilylthiophenol (t.Bg: Y S) 10 afford 4-trimethylsilylphcnyl vinyl sultide (134g; l.'=CH CH,).

All 3 chlorine atoms of phosphoryl chloride are rep-laced in its reaction with trimethylsilyl-phenolates 135 to give 136 (64%?t3.

135

137

[(H3ChSi-C6H4-0]3P=O + 3 NaCI

136

----? - HCI

(H3ClJSi-QCOOH

NH-CHz-COOH

138

SYNTlIESIS

Amines undergo reactions with electrophiles analo-gous to the hydlOxide compounds. N-Alkylation (4496) is found to occur in the reaction of 137 with ehloroaeetic acid314. N-Aeylation (9096) takes place excIusively in the re-action of 139 with methyl dichloroacetateJ (J7.

139

140

Anilines 141 readi Iy reaet with acetie anhydride to give aeetanilides 1,12 (90100%)243,245.25''.314.

141

142

Tertiary amines 143 can be converted to the quater-nary iodides 144 without desilylation reactionsm oe-curring simultaneously.

D(CHZ)ll-N(CH 3)2 (H3ChSi -

143 r ; 0, 1 Je

O(CH2)n-~(CH3h (H3C13Si

144

5.4. Condensation R(·actions

Aromatic earbonyl eompounds earrying trimethylsi-lyl su bstituents ur dergo an types 01' conventional earbonyl reaetions without desilylation wh{:n carried ()ut in slightly aeidie or basie medium. Since the for-mation of oximes, hydrazones, and semiearbazones ete .. whieh are also used to eharaeterize tbe eom-pounds, proeeeds a, usual, these reactions will not he diseussed here. Benzoin condensation29b, aldol reactious2'J(" 315, and glyeidie ester syntheses JI6 employing 4-trimethylsi-lylbenzaldehyde (122c) also proL'eed as expeeted. Various pyrimidones such as 148m , quiuoxalines 149 1lX, thiazolidines 15031

", as weil as numerous tri-

November 1979 Preparation 01' Aryl- and lIeteroaryltrimethylsilanes R67

KCN o OH

(H3ChSi-Q-g-tH-Q-Si(CH3h

o {H3Ch Si-Q-g-H

122c

methylsilyl-substituted phthalocyanin, indigoide, and triphenylmethane dyes have been prepared by condensation reactions using the appropriate trime-thylsilyl carbonyl compounds204.297.314.

R1

148

H

In ,~ (H3 C)3Si"-"'S,,/\ J

R S

150a R = H (70%)

b R = eH3 (51%)

149 a Y = 5 (92 %)

b Y = 0 (92 '10)

Alcohols of the type 151 in the presence of various catalysts (aluminum oxide 300-340", 39_52%2x7.m; potassium hydrogen sulfate, 240 0

, 43%65; phospho-rus pentoxide320) can be converted into styrenes 152 by thermal gas phase condensations.

151

catalyst, \J )

- HzO

152 a R = H b R = CH 3

Elimination of water occurs when trimethylsilyl-phthalic acid or trimethylsilylphenylthienylcarbinols are heated to yield the corresponding anhydride (100% )204 or ethers (30%)2<)1, respectively.

145

146 a R' = H, R2 = C6Hs b R' = R2 = H, CH 3, t-C,Hg C R' R2 = -(CH21,-

'- __ -I

147 a R3 = OCzH s (50 '101

b R3 = C6HS (67 %1

5.5. Oxidation Reactions

Methylbenzenes 153 (R 1 = H), benzyl alcohols 154 (R1 = H), and benzaldehydes 155 (R1 = H) can be oxidized with increasing ease by various agents to af-ford the benzoie acids 156. However, it is more diffi-cuh to stop the re action at the carbonyl compound 155; mixtures of acetophenones 155 (R 1 = eH;) and acids 156 are obtained from ethylbenzenes 153 (R 1= eH J ). Oppenauer oxidation of 154 (R I =C,H,) leads to the benzophenones155 (R 1= C(,H,). Mild oxidation ofthe methylbenzenes 153 (R 1= H) in ace-tic anhydride gives the benzaldehydes 155 (R' = H), available via the diacetate intermediate (Table 25).

R1 R1

R2~R1 I I

H-C-OH c=o R2~ R2~ vI ~ vI ~ vI

R3 ~ R3 ~ R3 ~ R4 R4 R4

153 154 155

156

Furthermore, 4-trimethylsilylbenzaldehyde (122c) is obtained from the p-substituted benzyl bromide 62c by employing the SommeletJOX or Hass-Bender reac-tion (87%)250. The corresponding terephthalic. iso-phthalic, and phthalic acids are formed (77-n%)204112 in the oxidation 01' xylyltrimethylsilanes using potassium permanganate in pyridine. Acetyl-furans and -thiophenes 157 are oxidized to give {t-

E{6E{ Dieter Häbich, Franz Effenberger

Tablc 25. Oxidation Rca<:lions Oll Sidc Chains of Aryltrimcthylsilanc, ------~_._._-~ --

Sub,trate R' R' R' R'

153 11 (II,CI8i J[ 11 153 11 11 11 ( 11 Cj,Si 154 H H fI (lIl),Si 155 11 H (II,CLSi 11 155 11 11 11 (IIC),Si 153 11 II,C CO Nil " (IIChSi 153 II,C 11 (II,ChSi 11 153 II ,C ill,Cl.Si 11 11 153 B,C 11 11 (1I.C),Si 153 11 O,N 11 (II·Cl,Si 154 e"II" 11 [I (I LCj,Si

-_.'" -- .. -

keto aldehydes 158 by using selenium oxide\IX or to earboxylie acids 159 by using sodillm hypoio-dide 2<J\.

J[).. (H3CbSi Y C-CH3

11 o 157 a y : S

b y : 0

J[).. (H3CbSi Y C-CHO

11 o 158 a y = 5 173%)

b Y : 0140%)

J[).. (H3ChSi Y C-OH

11 o 159r: 0

The epoxidation of 4-trimethylsilylstyrene lIsing per-benzoie acid (50~iY'" the oxidation of 2-. 3-, and 4-trimethylsilyldibenzothiophene 141.1 q using hydro-gen peroxide to give the corresponding sulfones (42-9R'lf,), and thc oxidation 01' 2- or 3-trimethylsilyIA-amino-phenol 121 with potassillm dichwmate/sulfll-rie acid to yield the eorrcsponding p-benzo411inones are further oxidation reaetions involving functiollal gWlIps 01' aryl- and hetewaryltrimethylsilanes, The oxidation 01' 3-nitwso-4-trimethylsilylpyrazole leads to the nitro compound 2hl

•

The oxidative introdlletion of oxygen fi.ll1ctions illto the nllcleus has heen applied in the preparation 01'

160

exSi(CHlb 1 +

N 0 H

162

(CH;COl!O a Si(CH 3h or POCI, "I -~ w >j-a

161

n Si(CH 313 1 +

o N' H

163

o )tySi(CH3h tJ N

H

164

SYNTIIFSIS

_._---_._- ---------- _ .. --_ .. _-- -- ----~- -_.- ----.

Oxidising P'oduel Yicld Rt'fcrcncc agent f'Y,j

.---_ .. _---_ .. --_.-_ .. _----- .

KMnO, 1:;6 21 16g KMn(), 1:;6 74 85, 30R KMno', 1:;6 310 0, 1:;6 WO .HO 0., 1:;6 WO 310 KMnO, 1:;6 85 310 Ca(:O,/0, 1:;5+156 15+ 11 133. 249 Ca<..' 0 ,/0, 1:'5+ 156 11 + 12 133, 249 ('aCO ,/0;. 1:;5 j 156 20 t R 249 CrOjAc,O 1:;5 19 314 AI«)('411,,-f) , 1:i5 23 295

- - ----_._-- _ ..

the pyridones 162-164 from 3-pyridyltrimethylsilane (160)1)4 and 01' 2-trimethylsilyl·p-benzaquinone from 4-aminophenols using potassillm dichromate/ sulfuric acid J22 .

Razuvaev et aL·)X.214.J21 have exhallstively investiga-ted the one-eleetrcn oxidation of sterieally hindered silieon-eontaining phenols 165 [R" R 2= eH;, i-CH7 , (-C4H'h Si(CH1h. ete.] with various agents [e.g. lead oxide, potassium hexaeyanoferrate(III), copper/pyridine/oxygen, I-butyl ether, phenylmer-cury(lI) hydroxide, ete.). The reactlOn goes through the intermediate (ree phenoxy radicals 166 whieh rearrange by migration 01' the trimethylsilyl group and lIndergo ~,ubsl:quent dimerization to afford the 2,2'-bis[trimethylsiloxy]biphenyls 167, Trimethylsi-Iyl-substituted quinones are t<.)und as by-produets.

165 166

2. dimerization )

167

5.6. Rcductioß Reactioßs

Metal hydrides, Sl ch as lithium aluminllm hydride, sodium borohydride etc, do not atleet the carbon-si-licoll bonds in ar:lltrimethylsilanes, They therefore provide a eonvenient method for reduetion of va-riolls funetional g 'OllPS, Using sodium borohydride the conversion of trimethylsilylaeetophenones into thc alcohols6

'i is possible under mild eonditions as weil as thc hydrog ;nolytic c1cavagc of trimcthylsilyl-thienyl-thiazolidines (68·71 ~V.I )1I4. Employing the more reactive lithium aluminum hydride. trimethyl-

November 1979

silylaryl derivatives of carboxylic acids and serine can be reduced to yield the corresponding alcohols (up to 90%)307. Corresponding nitriles are reduced to primary amines29b,307. N-Substituted amines of the type 169 are obtained by reduction of acyl amides 163

or by reductive cIeavage of 168 using lithium alumi-num hydride324

•

LiAlH 4

79- 84 Of,)

Reduction of trimethylsilyl-substituted phosphine oxides by lithium aluminum hydride gives the phosphines277 .

Other procedures for the convenient preparation of benzyl alcohols from benzaldehydes are, 1'01' exam-pIe, the treatment with tin(ll) chloride/hydrogen chloride296

, normal or crossed (formaldehyde/OH ') Cannizzaro reactions2%,325 and the reduction by tri-alkylsilanes in the presence of zinc chlorideJ2{,.

Reduction processes are the most important methods for the preparation of aromatic amines. This also ap-plies to the trimethylsilyl derivatives. Thus. azo com-pounds 170, nitroso- 171, or nitroaromatic com-pounds 172 can be converted into the amines 173 if the appropriate reducing agcnts are applied (Table 2(-' ).

R')P R2VR4

R3

170 a x = N=N-C6Hs

171 x = NO

172 x = N01

173

Preparation 01' Aryl- aud Heteroaryltrimethylsilanes

5.7. Metal Complexes 01' Aryl- and Heteroaryltrimethylsi-lanes

By the complexation 01' the 1T-system of aryl- or of the nitrogen atom of heteroaryltrimethylsilanes. the reactivity of the carbon-silicon bond can be drasti-cally altered.

Metallation of (ll-benzene )-( 17-pentafluorobenzc-ne)chromium with n-butyllithium and bis [benze-ne)chromium with n-butyllithium/tetramethylethy-lenediamine and subsequent silylation atTords [(Cr.Hh )Cr[C6 Hs Si(CH;h)l (n~!(;)m and [C6H., Si(CH 3hbCr (37%)32, respectively. Further-more. oxidation of the chromium atoms in these complexes can also be used to cause a strong varia-tion in the reactivity of the carbon-silicon bond.12S. The chromium tricarbonyl complexes of phenyltri-methylsilane and the bis[trimethylsilyl)benzenes 64a-c are fonned when these compounds are heated together with hexacarbonylchromium329,1\0.

Trimcthylsilylhcnzcnc <:hromium Tricarhonyl "": A mixture of hcxa.:arbonylcbromium (2,2 g. 10 mUllli) anJ phenyl-trimethylsilane (tu ml) is maintaincd at 170- 175 ((Ir 3tJ h unJer an argllli atmosphcre in a Ilask equippcd with an air condens.:r toppeJ with a water-cooled clilldcnser. During thi> timc the hexa.:arbonyl-~hr1l111iu11l wh ich sublimes into the air cllndenser is pcriodi~all)

pushed back iuto the rcaction tlask with a long spatula. A ydhlw wlour dcvclops slowly in the rcactilln mixture. and a small anwunt llf solid is fÖrmeJ. Thc 11lixture is then cOliled and diluted with et-her (1001111). Filtration through a short column 01' dcactivatcd alu-mimt is flillowcJ hy removal 01' volatiles at redun:d prcssurc_ Thc ycllow crystallinc rcsiJuc is recrystallized frOI11 aqucolls cthanlll tn give lhe prodU':l: yidJ: O.5tJ g (20'),,): m.p. 72 73. An analytical sam pie was suhli11lcd at 60 -65 /O.tl1 torr.

Ferroceny1trimethylsilanes 175 [R 1 = H. R ~ = Si(CH,h: 50;?!;)"1 are prepared from cyc\open-tadienyltrimethylsilanes 174 using n-butyllithium and iron( 11) chloride. Metallation of ferrocenes 176 (R 1= H) with sodium 132 or n-butyllithium 33-u14 and subsequent silylation affords mixtures 01' 175 (R 1 =R 2 =H; 19-23%) and 175 [R1=H.

R 2 = Si(CH I),; 27-50%); in the case of (dimethylami-

Taille 26. Trimethylsilyl-Substitutcd A11linohenzcncs 173 via Rcdllction 01' Am. Nitroso. ur Nitro CompounJs -~-" ,--._~.---------------

Type R' R2 R' R' RcJucing YiclJ Refcrelll'c Agent [",·1

_._._----,-----~---------~~-- - - .~ - -- ------ -- -- --- --_ .. __ . 170a Il (H,C),Si Oll 11 Na2S,O, 25X 1701l (H,C),Si H Oll 11 Na,S,ü, 95 257 171 (H,C),Si H 11 Oll Pd/c' 11, 257 171 (H,C),si 11 N(CII,), H Pd/Co 11.- 2-l5 172 (H,C),Si 11 H 11 Rancy-Ni/ll, X3 144 172 11 (H,C),Si 11 11 Rancy-Ni/II, 85 71). 1-l4

I'J/c, 11., 243. 265 172 H 11 (II ,C),Si 11 Rancy-NijH, 75 N.144

Pd/Co 11 2 2-l3 172 (II,ChSi fI CI 11 Raney-Ni/lh 75 271 172 NHCOCI-I, 11 (lI,C),si 11 Pd/Co 11, 24.1 172 (ILC),Si H (lI,Cj,N 11 Pd/C. 11, XI> 245 172 CH, H 11 (11 ,C),Si Rancy-Ni/II, l)() 314

870 Diete) Häbich, Pranz Effenberger

no)-methylferroeene 176 [R ' =CH 1N(CH,hl "ortho­metallation" favours seleetive reaction to give 175 [R ' =CH2N(CH 1b R2 = H; 79%]13',

2Q H Si(CH3h

n-SuLi/FeCt2

174

1. Na 0, n-C4HgLi 2. (H3CbSiCl 175

176

The methiodide of 175 [R 1 =CH2N(CH,h, R2 =, H] readily undergoes nudeophilic substitution of the trimethylamino group by aqueous hydroxide (85%), phenoxide (85%), aniline (95%), and piperidine (66%)1.15. The reaction 01' the 'lT-cyc!opentadienyl-irondicarbonyl anion with pentafluorophenyltrime-thylsilane gives 177\3<>.

F F

@-Fe(COl?-ttSi(CH3l3 F F

177

The paUadium(Il)J37 and gold(l)33H complexes 178 and 180 of the silanes 94 and 179 are formed, when

94

Agent y

PdCI,(Cr,HsCN), S PdCI,(C"H,CNh NB Au(CO)el S C7~LNS GcCl, NCII,

M

'/, PdCh '/, PdCl, AuCI (,cel,

178

Yield

91 63 73 60

Refer-

337 337 33X 304

h, agenl/CH2Cl2 or C6H6, r.l. ~ ~.,~ ~--~-------7) ~.,~ 'N Si(CH313 "~ Si(CH3b

M

179 180 a M = i PdCl, (84 '/0)

b M = AuCl 192 '/0)

SYNTHFSrs

these compounds react with PdCI2(ChHsCNh, gold chloride or gold carbonyl chloride. Dichlorogerm-ylene complexes 178 are obtained in a similar way304. The carbon-silicon bond of aU complexes proves to be less reactive than that of the free sila-nes.

5.8. Misccllancous

In c!osing, some types 01' reaetions and compounds that do not readily fit into one of above categories should be mention ~d.

The phosphonic esters 181 reaet with phosphorus pentaehloride to yield the dichlorides 182 whieh ean be converted into the phosphine oxides 183 using Grignard agents or into the phosphonie acids, when hydrolyzed 277. 3\9.

181 182

183

Halogenation and .;aponification are simila.rly appli-eable to the trimethylsilylphenylmethanephosphona-tes277 • Similar to tte tertiary amines 143 (cf. Seetion 5.3.), the phosphinl~s and arsines 184 ean be eonver-ted into the corresponding quaternary iodides 185277, 27X, 3:19.

184a-c 185 a M " P, R = CH3 (40-50'10)

b M " P, R = C2HS (58'10)

C M " As, R = eH)

Dimethylarsino groups are introdueed into aromatie rings like most of the phosphorus substituents (cf. Section 4.4.). The organometallic compounds 186m

are involved as int,~rmediates.

186

187 \60 '/0\

November 1979

4-T rimethylsilyl- t -arsabenzene (189) can be prepa-red in 83% yield by treating 188 with arsenic(lII) chloride340•

188

189

Sulfonyl chlorides 191 are prepared from salts ofsul-fonic acids 190 employing phosphorus pentachlori-dem, thus enabling the preparation of sulfonamides 192252, }O'i.

pels ---?

190 191

192

Reactions involving halide exchange on tri fluoro-methylbenzenes 193,1,341 to give 194 and on ethoxy-silanes 195252 to yield 196 have been carried out.

193

195

6. Conclusions

HF ---;.

196

194 aar/ho

b para

Although the number of publications concerning aryl- or heteroaryltrimethylsilanes is increasing mar-kedly, it does not seem very likely that dramatically different preparative methods from those described here can be expected for this class of compounds.

Preparation 01' Aryl- and Heteroaryltrimethylsilanes 871

In contrast, the better understanding of their rea\.'-tions and, therefore, of the scope of their prepara-tive utility is still in its infancy and, thus. the system holds promise for interesting future developments si-milar to that of the chemistry of vinylsilanes and si-lyl enol ethers. It is hoped that this article has provi-ded so me stimulation tor achieving that develop-ment.

Re~eived: Fchruary 12. 1979

* Author to whom corrcspondcn~e should he addresscd, I E, W. Colvin. Chon. So('. Rev. 7. 15 (197R); a review with 250

ref~.

T. 11. Chan. I. Heming. Svnlhesis 1979, 761. a review with 170 ref~.

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'. C. Eahofll. Orgallosilicof/ Cornpounds. Butterwllrths. L,'ndon. 1<)60.

" C. Eahofll, R. W. Bott in Organometallic ('ornpounds or ehe (JroliP IV Elemellts. A. G. Mcf)iarmid. Ed .. Yol. 1. Part 1, M. Dckker fnc., New York. 1961i. p. 421. 423.

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4" A. I. J\1cyers. R. Gahel. E. I). ~1ihclich, J. Org. ('hent. 43. 1372 (197X).

. p A. E. Bey, I). R. Weyenherg,./. Org. ehen1. 30, 243(1 (llJ65). " F. Effenbcrgcr. K. E. Mack, K. Nagel, R. Nicß, Cllem. /l,.,..

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November 1979

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Preparation 01' Aryl- and Heteroaryltrimethylsilanes 873

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",' I. lIaiduc, H. Gilman, Rev. Roum. ChillI. 16,907 (1971): C. A. 75. 7690S (1971) .

11,(, K. Shiina. T. Brennan, ll. Gilman, .I. Orgwwmet. Che,1I. 11. 471 (1968).

167 I. llaiduc. H. Gilman . .I. Orglillo/llet. Chem. 14. 79 (196~). lt>X R. A. Benkeser, H. R. Krysiak, J. Am. Ch<!nl. '-\~o('. 76. 5t.J<J

(1954).

R74 Dieter lIäbich, Franz Effcnberger

Ih'.1 E. Cilydc, R. Taylor, J. ('Ilem. SOl'. PerJ..il1 Trans. 2 1973. 1632.

1/0 E. Reinlanll. L Langwielcr, Arch. Phartll. (JYeinheim. U:'r.)

308, 888 (197:;); C. A. 84. 74334 (1976). I/I K. Kuroda. N. Ishikawa. Nippon KaKaku Za.\shi 91. 4X'!

(1970): C. A. 73.66669 (llJ70). M. R. Smith. 11. Gilman. J. Or[!,llnOl1!ef. Cht'm. 42.1 (1972).

171 G. M. Davics. P. S. Davlc,-;, Tetrollet/roll I.elf. 33, 3~;07 (llJ72).

i74 K. P. C. Vol1hardt. L. S. Yce, .I. Am. (,heIlI. SOl'. 99, 2010 (1977).

I" P. A. Konstantinov. R. I. Shllpik. Zh. Ohsh"h. Khim. 33. I :!51 (1963); c. A. 59. tlll02 (1%3).

1,'(, L>. W. Slocum, P. L. (i-icrer..I. Org. ehen1. 3ft 41X9 (1')73),

S. F. Thamcs. J. E. M<:C1oskcy. J. lIelerocrd (·Ilem. 4. :46 (1 967).

Il\: S. F. Thames,J. E. tvfcCloskey,.I. flelcroc)'cl. ('heI11. 3.1 04(14(,6). 17" S. F. Thamcs ct al...I. lIele/'O<ycl. Chern. 9.12:;9 (1972). . I'" K. C. Frisch. R. M. Kary. J. Urg. ChelII. 21.931 (1956). 1;1 .I. C. POllll1licr. D. Lu<:as. J. Or[!,'lI1omel. (·Ilem. 57. 139

( 1973). I'>' P. Jutzi~ W. Sakriß. ehern. 811".106, 2Xt5 (lq73): C, A. 80, .~:)72

( 1974). ,,:~\ F. 11. Pinkcr!on, S. F. Thamcs . ./. lIetcrocrcl. ('hem. 9. 67

(1972). ",1 P. Jlltzi. H . .I.lIoilinann, C"em. ller. 106. 5'!4 (1973): c. A. 78.

14X029 (1973). '" F. H. Pinkertllll. S. F. Thamcii, J !feleroeycl. Chern. 8. ~!57

(1971\. J:-6 For a re..:ent papc~r sec: N. t\.1eycr. D. Sechach. A Ilg('w. ('ho.'ltl.

90,553 (1918); Angell'. Cl!em. Inl. I,·d. t:ng!. 17.521 (197X) p.:, C. Eaborn~ D. R. 1\1. Waltün. 1. ()rKalwmel. ehelll. ]. lh~

(1965). ISX Co T. Viswanathan. C. A. Wilkic . ./. OrXlIll(Jlner. (hetn. 54. 1

(1973). IX<) R. M. SanJifcr, C. F. Beanl, M. Perkins. C. R. I Jauser. ('Ilem.

Ind. (Lolldon) 1977.231. IIIi .I. Klein, A. Mculik-ßalan, J. Org. (·hem. 41, .H07 (1976). 1»1 C. Eahorn. Z. S, Satin, 1), R. N. Walton, ./. Org,tll1ofnel. Chi'l1l.

36.47 (1972). Ho' C. Eabortl. A. A. Najam. 1>. K. M. Wa!ton. J. Chef/!. So!'. I'er,

km Trans. 1 t 972. 24R I. ,'n A. F. Halasa. 1. OrgllfUJfncl. Chen1. 31. 36Y (1971). anti rcfcrcn-

.:es citcu therein. 1')1 I. lIaiuul'. 11. (/ilman. nu'm. Ind. (/,olldollj 1968, I27X. 1'1', I. Haiduc, H. (,ihnan, ./. ()rganonlct. ehenl. 1], P4 (t96):\). 1% C. Tanlbor~ki. I:. J S\)lo~ki . .I. Organol11CI. ('heI11. 10. ~X5

(196 7). "li S. S. Dua. H. (iilman,./. Orgallomcl. ('hem. 64. CI (1974). "~I' F W. (I. halon. 11. (Jilrnan. J. OrWIllOI1lC[. Chcrn. 10, i.lS

\19(7). 1'1') I. llaiduc, 11, (iiltnan,.r Org,llllolllel. ehcln. 12. Jl)4 (196X}.

2"" M. Kanazasbi. M. Takakusa, !Juli. ChclIl. SOl' . .Ipn. 27. ~.tl

(1')54); C. A. 49. XOl)6 (1955) '''' R. A. Benkcscr. R. A. llickner, 1). I. linke. J. illll. Cllcl1l. S",·.

80.2279 (19:'1X). }02 C. t"abnrn, 1), E. \VcbsteL .I. ehenl. SOl'. 1960, t 7Y.

C. Eahnrtl, I{ C. M,)ore, J. (·lIem. Soe. 1959. 3MO. .'04 11. Hopn: P. Ciallcgra, IIc-h'. Chiln. At'/a 51, 25J (t 96X): C /l,

68. 106060 (I%R). "'", F. B. Dcans. C Icab')f!l . .I. CIIl'm S",.. 1959. 2299. Ji)t, 11. A. Look. Urin\h Paleut 671553 (1952), I)(H\' tlll'ning 1.1d.:

C A. 47.4909 II'hl) :.)" C. Eahorn, 7.. S. Salih, 1). R. T\.1. W"ItOll . ./, ()rf.!t1flof}l('! Chl'11l.

36.41 (1972) . .''',. R. M. I,mail, Z. Nalur/()rw'h. [bi 19. 9(,4 (1964): (. 1. 62. 2790

(llJ65). ~'q" .I. L. Speier . .Ir.. {' S. Pall'lll 25X4751 (1952). I)"W ('\)f!ling

(orr .. C. 4. 46. '.9:::5 (1952) . 1. L. Speier. .I .4m~ (11<'/1/ . .'1(1('. 74. [1103 (1"~2).

:11 .I. I. Spci.:r. .Ir.. Hrtllsil Pa[enl (,~XHI7. hXXXIX (1'1'i3). II"W C,lTnlng Uu .. ( ,I. 47.4')(1'1 (19:'13).

SYN 1lllSIS

m C. Eaborn. Z. Lasocki, D. E. Webster. J. ehern. Soc.1959. 3034.

21 J 0. D. CO(>per, J. (lrg. Chml. 26. 925 (1 % I). 214 G. A. Razuvacv. N. S. Vasilciskaya. D. V. Muslin. J)o"l.

Akat!. Nauk SSSR 175. 620 (1967); C. A. 68, 29773 (196X). I. L. Khrzhanovskaya. N. S. Vasileiskaya. G. A. Ral.llVacv. Izl'. Akad. Nauk SSSR, Sero Kilim. 1972.2276: C. A. 78. 5X:'ItJ7 (1973). (1. A. Razllvacv ct aL Zh. Organ. Kilim. 6. 'iSO (1970); C. A. 73. 35435 (1970). G. A. RazlIvacv, I. L. KhrJ:hanovskaya. N. S. Valeiska~a, D. V. Muslin. /)",,1. A kad. Nauk SSSR 177. WO (1967): C. A. 68. 45 XX6 (1 <)M\). (1. A. KazlIvacv. 1\. S. Vasikiskaya. N. N. Vavilina. J. Orga-

1/01111'[. Chel1l. 80.19 (1974). 2" G. A. Razuvaev. N. S. Vasikiskava. 1). V. Mw,lin, J. ()rI<II110~

mel. Chel1l. 7, 531 (1967).' , G. A. Razllvaev. N. S. Vasilciskaya. N. N. Vavilina. Zh. Ohshch. Kilim. 44.135 (1974): C. A 80. IOX607 (1974).

_'16 L Arai, K, H. Park. O. f). ])avcs, JI., J. ()rJ!,1l11on1el. Chc1Il. t21. 25 (1976).

'" G. Silllchcn. J. Pt1ctschingcr. Angelt·. Chem. 88.444 (1976): /lngelt'. Clwm. 111[. Hd. J:·ngl. 15. 42X (1976).

21:-': (,. A. Razuvaev. N. S. VasJlciskaya. 1. L. Khri'hanl1V"ikaya. Zh. Obshch. Khim. 45.2434 (1975); C. A. 84. 5963R (1976).

~I') D. V. Muslin, er. r\. Razuval.:v, N. N. Va\>ilina. N. S. Vasikis-kaya. !zr. Akad. ,v'wk SSSR, SeI'. Khill!. 1975. IX2; C. ./. 82. 140253 (1975).

2~O D. V, Muslin, N. S Lyapina, A. P. Kut'.n, N, S. Vasileiskaya, Izr. Aklld. NI/u!< :., .. .,'SR, SeI'. Kilim. 1978, X9(); C. k 89. 435X:; (197X\.

)11 I. Arai, CL D. I)avcs, Jr.,.I. ehern .... \'(JC'. Chellt COl1l1l1ll11. 1976. 69.

:n E. Ifenggc. H. 1>. Fletka, ~lollalsh. eheni. t04, 1071 (1973): C. A. 80. 4XtJ93 (19741.

211 D, Seyferth, D. L. Whitc, J. Am. ('hefn. Soc. 94, 3132 (1972). 2M D. Seyfenh. D. I.. White. J. Or[!,anumel. (,h('m. 26. C 15

( 1971). .~.:" R. L. Hillanl JJJ, K. p, C. Vollhardt, AngelL Cheln. 87. 744

(1975): Angew. Chon. Inf. Ed. Engl. 14.712 (1975). ~J.(, \V. (j. L. Aalht~r~herg et al., 1. A 111. ehern. SOl'. 97. 5600

(1975). ))7 K. L. Billard 111. K. P. C. Vollharut. AIl[!,t'Ii. Chem. 89. 413

(1977): Angew. C/zu//. Inl. lid. Eng!. 16, 399 (1977). -'" R. L. Funk. K. P. C. Vollhardt. J. (I!cm. Soc. Cl!cm. ('omn/ull.

1976, R33. 22" W. Ilüod. C. lIoggzand. Chem. /Jer.93. 103 (1960); C. A. 54.

'1X39 (1960). U. Krücrkc, C. Hllllgfand. W. HübeL G. Vanhec. Chem. /Jer.

94. 2RI7 (1961): C. A. 56. X622 (1962). K. W.lIubcl, (;ern,an Palenl1142X67 (1963), European Kese-ar('h Associate, S.A.; C. A. 59. 6317 (19113).

}l() .1. !)alc, (,hCln. Ber 94, 2X21 (l961)~ C .. A. 56, 71S0 (1962), '1< J), Scyferth. 1). L. Whitc. J. Organu/1lel. Ch<'m. 34. 119

(1\)72). } \.: D. Scyfcrth. C. Sarafidis. A. B. Evnin . .1. (}rgaflornel. ('lIenl. 2.

417 (1964). 'H L. Birkofer, R. Stilkc, J. Or,l::anoI11cl. ('heIlI, 74, ('1 (1974); C.

.1. 81.91632 (1974). 'H Ci. Ouil1erlll et (11.. ]Juli. I\'/J(. Chi/tl Fr, 1973.17.19; C. A. 80.

4X 122 (1974).

:11>

I.. Birkotcr. M. hanf, (·hem. lIa. 105. 17~l) (1972): C. L 77. 34622 (1972). I . BirkofCr, M. '·rll1z. ('hem. fler. 100. 2hXI (1967\; C L 67. 90X67 (19117). 1>. Scyfcllh. T. (,. Hoou, .I. OrganulIl<'!. (!tcm. 29. C 25 (1971 I. I. Birh,I':r. R Stilkc. Chcm~ /Jer. 107. nl7 (1974); C. A. 82,

577119 (1975) . I . Birk"fcr. 1\ Hillcr. tl. lIhknhralll:k. ('/in1/. Ikr. 96. 32Xn (1%3): ('. 1~ (,0. 5:137 (1964).

'" 1\1. ,. l.appen . .I.~. Poland.1. C1lC/Il. S", fCl 1971. .19W.

Novcmber 1979

24' T. lIashimoto, Yakugaku Zasshi 80, 1399 (196(): C. A. 55,

5393 (1961). 24) A. I). Petrov, V. P. Lavrishchev, lzv. Akad. NauA. SSSR, Otd.

Khim. Nauk 1952, 1125: C. A. 48, 124!\ (1954). 241 Y. Sakata, T. Hashimoto, Yakugaku Zasshi80, 72X (1960): C.

A. 54, 24480 (1960). 244 A. D. Petrov, E. A. Chernyshev, 121'. A kad. Nauk SSSR. Old.

Khim. Nauk 1952, 1082; C. A. 48, 565 (1954). 24' T. Hashimoto, M. Seki, Yakugaku Zasshi 81, 204 (1961): C. A.

55.14340 (1961). 24'. A. D. Petrov, G. I. Nikishin, Im Akad. Nauk SSSR Ott!.

Khim. Nauk1952, 1128; C. A. 48, 1247 (1954). 247 O. F elix, 1. Dunogues, F. Pisciotti, R. Calas. A ng~w. Chl'lI1. 89,

502 (1977); Angew. Chell1. Inl. Ed. Eng!. 16,488 (1977). 24> F. 11. Pinkerton, S. F. Tahmes, J. /Il'terocyc/. (,hell1. 9, 715

(1972). 24<) R. G. Scverson, Chem. Eng. News 32, 1324 (1954). 151) R. Ci. Severson, R. J. Rosscup, D. R. Lindherg, R. D, Engberg,

J. AII1. Chem. So('. 79,6540 (1957). 2'il R. J. P. Corriu. B. J. L. Henner, N. l)uffaut, M. (hignon-Du-

bois, Bu/l. SOl'. Chim. Fr. 1977, 1249; C. A. 89, 24434 (197X). }',,,' R. W. Bott, C. Eahorn. T. Hashimoto, J. Orgllllolllct, ehenl. 3.

442 (1965). ", C. Eaborn, T. lIashimoto, Cl1I'1I1. Ind. (London) 1961. 10Xt. 2'·4 S. N. Bhattacharya, C. Eaborn, 1). R. M. Walton, J. Chet1/.

SOL'. ICI 1969, 1367. 2>:, Y. Sakata, T. lIashimoto, Yakugaku Zasshi 79, K72 (1959): (',

A. 54, 357 (1960). 2.,<, N. N. VIasova cl al., Lh. Oh.vht'h. Khim. 39, 2705 (1969); c. A.

72. 90562 (1970). 2"7 T. Hashinl0to, Yakugaku Zasshi 80, 1399 (1960)~ ('. A. 55,

5393 (1961). 2"~ T. l{ashinloto, Yakugaku Zasshi 87, 530 (t967); C. 4. 67,

54207 (1967). "", E. 11. Bartlett, C. Eaborn, D. R. M. Walton, J. (,hem. SOl'. ICI

1970, 1717. "" L. Birkofer, M. Franz, Chem. Ber. 104,3062 (1471): C. A. 76,

14633 (1972). "" J. L. Speier, J. Am. (,hem. So('. 75, 2930 (1953). ",I C. Eaborn, Z. S. Salih, D. R. M. Walton, J. Chelll. SOl'. Perkin

Tra ns. 2 1972, 1 72. 2M R. A. Benkeser, P. E. Brumfield, J. Am. Chem. SOl'. 7.\. 4770

(1951). 2(,~ T. lIashimoto, Yakugllku Zasshi 87, 524 (1967): C. A. 67.

54205 (1967). 2bl, For arecent paper see: Y. Limouzin. J. C. Maire, J. Organv w

met. Chelll. 105, 179 (1976). 267 F, B. Deans~ C. Eaborn. J. eheln. SOl', 1957, 49X, 21.' C. Eaborn, ./. Orgllnolllet. Chem. 144, 271 (1978). 21,') Y. Sakata, T. lIashimoto, Yakugaku Zasshi79, XXI (1959): C

A. 54, 358 (1960). 270 Y. Sakata, T. lIashimoto, Yakugaku Zasshi 79. ~7X (1959): C.

A. 54, 35R (1960). 271 1'. Hashimoto, Yakugaku Z(J.l'shi 87, 291 (1967): C. A. 67.

11533 (1967). 27J T. Hashimoto, Y. Sakata, Yakugaku Zasshi 79,1',75 (1959): C.

A. 54, 358 (t 9(0). 271 R. G. Neville, J. Org. Chem. 24, X70 (1959). 274 V. P. Kozyukov, E. F. Bugerenko, V. F. Mironov. Zh. Ohsht'h.

Khim.45, 1397 (1975); C. A. 83, 114547 (1975). J. D. Austin, C. Eaborn, J. D. Smith, J. Chem. So('. 1963, 4744.

27(, K. C. Frisch. 11. Lyons . .I. Anl. Chem. So<'. 75. 4117X (19:'3). R. W. Bott, B. F. Dowucn, C. Eaborn. J. ()rgllllOlI1~t ( 'hem. 4, 291 (1965). C. liaborn, 1. F. R. Jaggaru, J. ehern. Sm. IB]1969. 1\1)2. K. Dcy, C [ahorn, D. R. M. Walton. (}rgaf/()lI1elal. Chell1.

Srlllh. 1,1"1 (1970/71). c. J. Murphy. 11. W. Pm,t, J. Org. Chelll. 27. 14~6 (I'J61). S. Kohalll:1. Nipp"n Aw.:aku Zas.lhi 80.21-:4 (1')"'1): C I. 55. 43'19 (1%1).

Preparation of Aryl- and Heteroaryltrimclhylsilanes 875

!Xl U. V. Timofcyuk el al., /)okl. Akad. Nauk SSSR 168. 613 (19M); C. A. 65, 8947 (1966).

-'", R. A. Bcnkescr, 11. Landesman, J. Am. Chelll. So(. 71. 249.' (1949).

2X~1 N. A. Ampilogova~ R. A. Bogatkin, F. Y. Pervecv. Zh. Ohshch.

Khim. 42, 716 (1972): C. A. 77, 8X582 (1972) .. :).;) C. S. Rondestvedt. Jr., H. S. Blanchard . ./. Org. ('/zenl. 21. 229

( 1956). :S(, (r. Dcleris. J. Dunogues, R. Calas. J. Orgallonw1. eheni. 93. 43

( 1975). JX7 f. H. Winslow, U. S. Palent 2642415 (1953), Bell Tclepllllnc

Laboratories, Inc.; C. A. 47,9058 (1953). 2XX A. D. Petrov, E. A. Chernyshev. N. Ci. Toistikova. Dokl. Aklld.

Nauk SSSR 118, 957 (1958); C A. 52, 12787 (195);). !S" H. C. Brown, Y. Okamoto, T. Inukai, J. Am. CheII!. Soc 80,

4964 (l9511). "10 K. C. Frisch, U. S Palellt 2759959 (1956), General Electri.:

CO.: C. A. 51,7412 (1957). .'9(/ K. C. Frisch) U. S. Patent 2759959 (1950); C . .'1. 51, 7412

( 1(57). ."11 F. H. Pinkerton, S. F. Thames, J. Orgal!ofllel. (,hcm. 29, C 4

( 1971). }91 11. H. SZluant, S. Skcndrovich, J. A111. ehenl. SOl'. 76. 22~2

(1954). 2'1.' R. A. Benkescr. R. B. Curric, J. An,. ehem. SOl', 70, 17RO (1lJ48). 2'.14 J. R. Pralt. F. H. Pinkerton, S. F, Thames . .I. Orgllll0l11t.'{,

CheII!. 38, 29 (1972). ,," P. 1. Campagna, 11. W. Post, J. arg. ehern. 19,1753 (1954). 2% Y. Sakata, Yakugaku Zll.\'shi 82, 929 (1962): C. -I. 59. Ci53

(1963). "1/ B. N. [)olgov, N. E. Glushkova, N. P. Kharihlllllv. 1 zr. Akud.

Nauk SSSR. Old. Kilim. Nauk 1960. 351: C. .1. 54. 1()l156 ( 1960).

2'" P. J. Campagna, 11. W. Post, Red TraF. Chili!. Pan-lias 74.77 (1955); C. A. 50, X56 (1956). .

2'N E. H. Barlett. C. Eahorn, I), R. M. Waltl)n, U. S. (', F S. T 1.. ,·ilJ Rep. 701 102, 1969: U. S. Gorl. Res. Uere!o!,. Rep. 70, 63 (1970): C. A. 73,35473 (1970).

,(1) J. Chatt. A. A. Williams, ./. ehenl. So(', 1954.4403. '01 [). Sethi, R. n, Howclls, 11. (iilnlan. J. Organonlet. ('heIlI. 69.

377 (1974). M. R. Smilh, ,Ir., H. Gilman, J. Organofllcl. ('IIell1. 37, 35 (1972).

<02 F. H. Pinkenon, S. F. Thamcs, J. Il<'teroeyd C"('m. 7, 747 (1970).

101 J. G. Noltes, (i. J. M. van der Kerk, Red 7h1r Chili!. Pa 1.1'­

Bas81, 565 (1962); C. A. 57, H971 (1962). '04 P. Jutzi, 11.-.1. Hotrmann, K. H. Wyes, J. Orgal1oll!{'t. Chem.

81.341 (1974). "" L. Birknfer, M. han/.. Chem. Ber. 105. 470 (1972\: C. .'/. 76,

99747 (1972). '0" A . .I. Cllrnish, C. Eaborn, J. ehem. So<". Perkin Trans. ! 1975,

X74 (1965). 107 lJritish Patent 11 OX ts4X (t 96H), Yissum Research Dcvcloptnent

Cn. of the IIchrcw University 01' Jerusa\em: C. A. 69, 521X3 (196X).

ws Tzu-Shcn Lin~ Shih-llui Wu, Lin-Yüen IIsü, T'ung-Yin YB. !lUIl IIsueh Ilsu('h Pao 26, 7 (1960): C. A. 55, lX654 (1961).

10<) S. N. Bhattal'harya, C. Eaborn, D. R. M. Walton. J. Chal/. SOl'. lCl1968, 1265.

WJ T . .I. Maass, H. W. p,,)st, Reel. Tral'. Chinz. Pay.\-llas 81, xx (1962); C. A. 57, X53 (1962).

<I, K. C. Fris~h. P. J). S~hrol'C U. S. Palent 2647137 (1953\, Ge-neral Elel:tric Cl'.: <'. A. 48, 7635 (1 (54).

<12 11. lIopff~ P. Gallegra, lIelz'. Chim. Acla 51. 553 (I9cJX); C. .'1. 68, 105 2H5 (I96X).

\11 A. E. Canavan. C. Eahorn, ./. Chem. SOL 1959, 3751 III 11. Hopff. ll. (juyer. Jus/IIS l.ieh(f!,s ,,'/lII. CheIlI, 739. 144

(1'!70): C. A. 74,4621 (1971). \(' B. N. J)olgov, N. E. (llushkova, N. P. Kharitlll111v. I~I'. Aklld.

Niluk SSSR. ()rdel. Khim. NllUk 1961, 1069: (' .. / 55. ~71X2 ( Il}tl1).

::176 Dietcr Häbich, Franz Effenberger

"" V. F. Martynov. Jen-Shih Cho, Hua lJsueh llsueh l'ao 26. 18 (1960); C A. 55, 17611 (1961).

317 0, A. Zagulyaeva, E. A. Travintscva, V. P. MaJnacv, Izv. Sih.

Otd. Akad. Nauk SSSR. SeI'. Khim. Nallk 1975, 119: C. A. 83, 58936 (1975).

11~ S. F. Thamcs. J. E. McClesky, J. I!eten)(:vel. ehen1. 4, 371 (1967).

li" V. Bazant, V. Mlltousek, Collect. Czech. Chem. Commul1. 24. 3758 (1959).

~20 A. C. Boicelli, R. Danieli, A. Mangini, A. Ricci. G, Pirazzini, J. Ch"m. Soc. Perkin Trans. 2 1974, 1343.

\21 T. Hashimoto, Yakllgakll Zasshi 87. 535 (1967): C. A. 67, 54208 (1967).

"\" N. S. Vasileiskaya, L. V. Ciorbunova, O. N. Manlyshcva. G. N. Bortnikov, lzl'. Akad. Nal/k. SSSR. Sero Kilim. 1972.2755: C. A. 78, 111421 (1'173). I. L. Khrzhanovskaya, N. S. Vasilciskaya, Izv. Ahad. Nauk SSSR, Sero Kllim.tt>73. 71; C. A. 78. 135798 (1973). O. A. Razvaev ct al.. lzl'. Akad. Nal/k SSSR. Ser. Kil/II/. 1971,2392; C. A. 76,140947 (1972). G. A. RaZllvac~ cl al., Zh. Ohshch. Khim. 46, 2720 (1'.176): C. A. 86, 14017X (1 977). N. S. Vasileiskaya ct al., /21'. Akt/d. Nlilik SSSR, SeI'. Khlm. 1976.2770; C. A. 86, 155735 (1977).

21 Y. Salo. Y. fukami, H. Shirai • .I. Orgal1omer. Chcm. 78. 75 (1974).

21 ß. N. Dolgov. (l. K. Panina. Zh. Ohshch. Khin" 18, 112Y (1948); C. A. 43,1737 (1949).

SYNTH~.SIS

3)\ N. E. Cilushkova. l'..J. P. Kharitonov. lzv. Akad. Nauk SSSR, Sero Khim. 1967. 81'; C. A. 66, 1157h2 (1967).

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