MayLabDualPhotoredoxCatalysisinOrganicChemistry
Reviews:(a)Chem.Rev.2013,113,5322—5363(b)J.Org.Chem.2016,81,6898—6926(c)Acc.Chem.Res.2016,ASAP,DOI:10.1021/acs.accounts6b00351
Po-AnChen10/18/2016
RuII
N
N NN
NN
2+
Ru(bpy)32+
RuII
N
N NN
NN
N
N
N
N
N
N
2+
Ru(bpz)32+
IrIII
N
N N
Ir(ppy)3
IrIII
N
NN
N
Ir(ppy)2(dtbbpy)+
t-Bu
t-Bu
+
IrIII
N
NN
N
Ir[dF(CF3)ppy]2(dtbbpy)+
t-Bu
t-Bu
+F3C F
F
F
FF3C
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
RuII
N
N NN
NN
2+
Ru(bpy)32+
• AbsorpFonat452nm(visiblelight)• Stable,long-livedexcitedstate(τ=1100ns)• Singleelectrontransfer(SET)catalsyt• EffecFveexcitedstateoxidantandreductant
• MaxabsorpFonat375nm(visiblelight)• Long-livedexcitedstate(τ=1.9μs)• Singleelectrontransfer(SET)catalsyt• EffecFveexcitedstateoxidantandreductant• Tripletenergyof56kcal/mol-1
Advantages:Excitedspeciesservedasbothoxidantsandreductants.Lowcatalystloading.RadicalintermediatescouldbegeneratedatmildercondiFon.Organicmoleculesgenerallydonotabsorbvisiblelight.
IrIII
N
N N
Ir(ppy)3
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
MLCT=MetaltoLigandChargeTransfer.ISC=IntersystemCrossing
Ref:MacMillanetal.Chem.Rev.2013,113,5322—5363ForIr(ppy)3:MacMillanetal.J.Org.Chem.2016,81,6898—6926Jablonskidiagram:h^p://www.shsu.edu/~chm_tgc/chemilumdir/JABLON.GIF
RuII
N
N NN
NN
2+
RuIII
N
N NN
NN
3+
eg*
π*
t2g
Ru(bpy)32+
Ground State
MLCT+
ISC
eg*
π*
t2g
*Ru(bpy)33+
Excited Statelowest-energy triplet
MLCT state
oxidant
reductant
E1/2*II/I
= +0.77 V
E1/2III/*II
= −0.81 V
eg*
π*
t2g
Ru(bpy)3+
eg*
π*
t2g
Ru(bpy)3+
metalcenter
ligandcenter
452 nm
SimplifiedMolecularOrbitalDepicAonofRu(bpy)32+
Jablonskidiagram
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ru(bpy)32+ *Ru(bpy)3
2+
E1/2III/*II = −0.81 V
A
ARu(bpy)33+D
D
E1/2III/II = +1.29 V
D
D
E1/2*II/I = +0.77 V
Ru(bpy)3+
E1/2II/I = −1.33 V
A
AReductiveQuenchingCycle
OxidativeQuenchingCycle
OxidaAveandReducAveQuenchingCycleofRu(bpy)32+
Ru(bpy)32+
excitation λmax = 452 nm
*Ru(bpy)32+emissionquenching
λmax = 615 nmRu(bpy)32+Ru(bpy)33+
or Ru(bpy)3+
FluorescenceQuenching(Stern-Volmer)Studies
CommonoxidaFvequenchers:viologens,polyhalomethanes,dinitro-anddicyanobenzenesCommonreducFvequenchers:terFaryamines.
Ref:ModernMolecularPhotochemistry;Benjamin/Cummings:MenloPark,CA,1978
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
EarlyWork:
Ph
OSMe
Me
BF4
N
CO2Et
Me
EtO2C
MeMe
[Ru(bpy)3]Cl2Ph
O
Me99% yield
Kellogg, 1978 - Reductive desulfuration
Deronzier, 1984 - Photocatalytic Pschorr reaction
CO2HN2
CH3CN, hυ
[Ru(bpy)3]Cl2CH3CN, hυ
CO2H
OR
ONPhth
SePhR
R
O
R1
N-(acyloxy)phthalimide
HR
ClR
Hydro-decarboxylation
Chlorination
Phenyl-seleneylation
Conjugate addition
±e
99% yield
R
intermediate
Okada, 1991 - Reductive decarboxylation of redox-active esters
Ref:TetrahedronLeB.1978,19,1255—1258J.Chem.Soc.,PerkinTrans.21984,1093—1098J.Am.Chem.Soc.1991,113,9401—9402
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:JACS,2008,130,12886—12887Science,2008,322,77—80 JACS,2009,131,8756—8757
RecentlyWork:
Ph
O
Ph[Ru(byp)3]Cl2 (5 mol%)
LiBF4, i-Pr2NEt
275 W CFL bulb
50-98% yield, 4:1 to 10:1 dr13 examples
O
H H
O
Ph
O
Ph
(a) Yoon, 2008 - [2+2] Enone cycloadditions
H
O
R
CO2EtBrNH
NMeO
Me t-Bu
•TFA
(20 mol%)
photoredox catalyst (0.5 mol%),2,6-lutidine,visible light
H
O
RCO2Et
63-93% yield88-96% ee
12 examples
(b) MacMillan, 2008 - Asymmetric catalytic α-alkylation of aldehydes
CO2Et
CO2Et
(c) Stephenson, 2009 - Reductive dehalogenation of activated alkyl halides
NN
CO2Me
BrCO2Me
HBoc
[Ru(byp)3]Cl2 (2.5 mol%)HCO2H, i-Pr2NEt
14 W CFLN
NCO2Me
HCO2Me
HBoc
79-99% yield10 examples
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Photoredoxcatalystswithoutco-catalysts
NetReducFveReacFon-ReducFonofElectron-DeficientOlefins-DehalogenaFon-ReducFonofHydrazidesandHydrazinesNetOxidaFveReacFon-OxidaFonofBenzylicAlcoholstoAldehydes-OxidaFveHydroxylaFonofArylboronicacids-NetNeutralReacFons-AtomTransferRadicalAddiFons(ATRA)Cycle.
Ref:MacMillanetal.Chem.Rev.2013,113,5322—5363J.Org.Chem.2016,81,6898—6926
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:MacMillanetal.JACS,2009,131,10875—10877JACS,2010,132,13600—13603ACIE,2015,54,9668—9672
PhotoredoxCatalysisandEnamineCatalysis:TheAsymmetricα-AlkylaAonofAldehyde
H
O
R
FGXphotoredox catalyst (0.5 mol%),
2,6-lutidine,visible light
H
O
RFG
organocatalyst (20 mol%)
NH
NMeO
Bn Me
•TFA
NH
NMeO
Me t-Bu
•TFA
examples of organocatalyst
H
O
R
Cyanoalkyation63-95% yield90-98% ee
±e OC
H
O
R
CF3
Trifluoromethylation61-86% yield93-99% ee
via:F
FF
H
O
RAr
Benzylation68-91% yield82-93% ee fac-Ir(ppy)3 H
O
RCN
R1
Ru(bpy)32+
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
GeneralMechanismofDualCatalysisSystem
Ref:MacMillanetal.Chem.Rev.2013,113,5322—5363ForIr(ppy)3:MacMillanetal.J.Org.Chem.2016,81,6898—6926
H
OR
R
N
NMeO
Me t-Bu
FG
R
N
NOMe
t-Bu Me
FG
Ru(bpy)32+
*Ru(bpy)32+
oxidantRu(bpy)3+
reductant
SET
OrganocatalyticCycle
PhotoredoxCatalyticCycle
FGX
FGX− +
SETvisiblelight
FG
Me t-Bu
MeON
N
RH
FGR
O
H
NH
NMeO
Me t-Bu
Si faceexposed
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:JACS,2009,131,10875—10877JACS,2010,132,13600—13603ACIE,2015,54,9668—9672
n-hex
O
H
94%, 92% ee
n-hex
O
Hn-hex
O
H
86%, 90% ee78%, 87% ee
BenzylationNO2
NO2NN
N Cl
CO2Etn-hex
O
H
CO2Et
93%, 90% ee
CO2Et
O
H
CO2EtCO2Et
n-hex
O
HPh
92%, 90% ee80%, 88% ee
CO2Et
Me
Trifluoromethylation
n-hex
CF2CF3
O
Hn-hex
O
H
F
C6F5
F
n-hex
CF2CO2EtO
H
73%, 96% ee 85%, 98% ee 89%, 99% ee
Cyanoalkyation
CN
O
H
Ph92%, 93% ee
CNn-hex
O
H
95%, 95% ee
n-hex
O
H
CNNMe
Ts
73%, 95% ee
Alkylation
Selectedexamplesofdualphotoredoxcatalystandorganocatalyst
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Nature2016,532,218—222Science2007,316,582—585
O
R1Me
NR2
Arn
organocatalyst (20 mol%)[Ir[(dF(CF3)ppy]2(dtbbpy)]PF6 (1 mol%)
benzoic acid (0.4 eq), PhMe, white LED
O
n
R1 NR2
Ar52-92% yield64-90% ee
N
R1n
HN
radicaladdition
β-scission
N
n
HN
R1 NAr
R2
fast N
n
HN
R1 NAr
R2
NH2
N
N
Mes Mes
Nfast SET from carbazole "e− pool"
Rapid tautomerisationfrom enamine to imine
IrIII
N
NN
N
t-Bu
t-Bu
F3C F
F
F
FF3C
[Ir[(dF(CF3)ppy]2(dtbbpy)]+
organocatalyst
O organocatalyst (20 mol%)Ir(ppy)3 (1 mol%)
1,4-dicyanobenzeneDABCO, HOAc, H2O,
DMPU, 26 W CFL
O
CN82% yield50% ee
Asymmetric β-arylation of ketones
N
NH2N
NRR
3π-electronradical cation
H+
NRR
5π-electronβ-enaminyl radical
O
direct β-carbonylfunctionalization
via:
single-electronoxidation
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:JACS,2014,136,16986—16989ForIr(ppy)3:J.Org.Chem.2016,81,6898—6926
PhotoredoxCatalysisandthiolcatalyst:ACouplingofBenzylicEtherswithSchiffBases H H
OMe
C-H BDE = 85.8 kcal/mol
HS CO2Me
C-H BDE = 87.2 kcal/mol
Physcial properties that enable thiol-photo C-H activation
weak C-H bonds: activation via bond energies, H atom transfer
HS
O
OMe
base
*Ir(III)(ppy)2(dtbbpy)+
redox cat.photoinduced
e− proton-coupledelectron transfer
PCETS
O
OMe
thiyl radicalactivation mode
OMeCN
CN
photoredox catalystthiol catalyst
OMe
CN
NPh
OMe
photoredox catalystthiol catalyst
NPh
OMe
NHPh
OMe
β-amino ether(racemic)
Diret arylation of benzylic ethers with cyanoaromatics
Merger of benzylic ethers with Schiff bases via photoredox
NPh Ir(III)(ppy)2(dtbbpy)+Ir(II)(ppy)2(dtbbpy)
reductant
SET
NPh S CO2Me
HAT
HS CO2MeOMe MeO
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Sanfordetal.JACS.2011,133,18566Chem.Rev.2010,110,1147
PhotoredoxCatalysisandPalladium:C-HArylaAonwithAryldiazoniumSalts
N
MePd(OAc)2 (5 mol%)
IPh PhBF4−
AcOH, 100 oC N
Me
Ph88%
w/ophotoredoxcatalystvia:
2 e−oxidant
"R+" PdIVN XL
PdIIN XL
R
X
N
Ru(bpy)3Cl2 (2.5 mol%)Pd(OAc)2 (10 mol%)
Ag2CO3 (0.1 eq)MeOH, 25 oC,
visible light
N
Ph76%
Me N2BF4
+
4 eq.
Me
via:
PdIIIN X
LPdII
N XL
Ph Ru(bpy)32+Ru(bpy)33+
SETPdIV
N XL
R
X
w/photoredoxcatalyst
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Sanfordetal.JACS,2012,134,9034—9047Ru(bpy)32+
*Ru(bpy)32+
oxidantRu(bpy)3+
reductant
SET
CoppercatalyticCycle
PhotoredoxCatalyticCycle
SETvisiblelight
CuX(I)
F3C I
CF3 + I−
CuX2(II)
CF3
CuX2(III)F3C
B(OH)2 B(OH)2(X)
CuX2(III)F3CAr
CF3
R
B(OH)2CuOAc (20 mol%)
Ru(bpy)32+
CF3I, K2CO360 oC
R
CF3
PhotoredoxCatalysisandCopper:TrifluoromethylaAonofBoronicAcid
Mechanism:
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
PhotoredoxCatalysisandGold:CurrentStateoftheArtinthetransformaAon
Review:Gloriusetal,J.Org.Chem.2016,81,6898—6926
Cl(I)AuR3P
ArN2BF4(or Ar2IBF4)
photocatalystvisible light
Au(III)Cl
R3P Ar
Key Cationic Au(III)Arspecies
OHR
n
OR
nAr
PRH
O
RP
RAr
O
RRing Expansion P-H Bond
Functionalization
R Ar
R H
R TMSor
C(sp)-H BondFunctionalization
R1 R2H2O R1
O
Ar
R2
AlkyneHydration
B(OH)2
Ar
C(sp2)-C(sp2)Coupling
•
R2
CO2tBuR1
O
Ar R2
OR1
AllenoateCyclization
OH
RO
R
ArCyclization of
o-alkynylphenols
OH
R2
R3
R1R1
O
Ar
R3
R2
Meyer-SchusterRearrangement
n = 1-2
OR[Au]
Hvia:
•
R2
R1
O
O[Au]via:
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Review:Gloriusetal,J.Org.Chem.2016,81,6898—6926
Au(I)L
Nu−Au
Nu
L
oxidation Au
Nu
LXX
Trans-metalationR-M/H
Au
Nu
LXR
ReductiveElimination
R
NuDifunctionalized
Prodcuts
Protodemetalation
H
Nu
Hydrofunctionalized Products
+Nu−
Nu
Nu
HomocoupledProducts
Au(I) L
NuAu(I)L
Nu H
HRadicalAddition
NuAu(II)LAr
NuAu(III)L
Ar
Ar
NuDifunctionalized
Products
π-system
ReductiveElimination
Au(I)/Au(III)CatalysisCycle
Ru(bpy)32+
*Ru(bpy)32+
oxidant
Ru(bpy)3+
reductant
SETPhotoredoxCatalyticCycle
SET
visiblelight
ArN2BF4-N2, -BF4− Ar
Ar
Mechanism
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Chem.Rev.2013,113,5322—5363ForIr(ppy)3:J.Org.Chem.2016,81,6898—6926
PhotoredoxCatalysisandNickel:SelectedC-CbondformaAon
Br
Radical coupling partner
NickelCatalytic
Cycle
*Ir(III)oxidant
Ir(II)reductant
SET
PhotoredoxCatalyticCycle
visiblelight
LnNi0
Ni(II)Ln
BrAr
R R
Ni(III)LnAlkylBr
Ar
Ni(I)Ln Br
Ir(III)
SETR R
CO2H
R R
R
R
R
R
O
OH
RNPh
H
R
with Doyle
with Doyle
R
R
Si(cat)2−X+
R
R
BF3KMolander
Fensterbankand Goddard
Molander
±e Ni
ArX
R
R
Ar
R
CO2H
NHBoc
Br
R
[Ir[(dF(CF3)ppy]2(dtbbpy)]PF6 (2 mol%)NiCl2•glyme (2 mol%)
(S,S)-(4-tBu-C6H4)-semicorrin (2.2 mol%)
TBAI, Cs2CO3, 34 W blue LEDsR
Ar
NHBoc46-84% yield82-93% ee
Enan)oselec)vedecarboxyla)veC(sp2)-C(sp3)coupling
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Science,2014,345,433—436JACS,2015,137,2195—2198Org.LeB.2015,17,3294—3297Chem.–Eur.J.2016,22,120—123
Molander’swork
BocN
Ar Ar Ar Ar73% 92% 0% 93%
R1
R2
BF3K+
BrIr cat. (2.5 mol%)
NiCl2•dme (5 mol%)dtbbpy (5 mol%)
1.5 eq Cs2CO3, 26 W CFL
R1
R2
ArR3
Ar:
OMe
CN NN
N
Cl
95% 80% 88%
JACS, 2015, 137, 2195—î2198
Chem. - Eur. J.2016,22,120— î123
CF3
Ar BF3K
BrR
CF3
ArR
CF3
Ar
Cl
CF3
Ar
NBoc
63% 56%
CF3
Ar
66%
*whenachiralligandwasemployedandcomputaFonalstudiessuggestthatrapiddissociaFonoccurs.
HRR
R
R
BF3 R
RNiLn
NiLn
single-electrontransmetalation
low EAct
High EAct
conventionaltransmetalation
Conventionalapproach
SETapproach
*high temp.*strong base*isomeriaztion*β-hydride elimination
*room temp.*lower barrier*regioselective*minimal side products
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:JACS,2016,138,475—478Alsosee:ACIE,2015,54,11414—11418Org.LeB.2016,18,1606—1609
Ru(bpy)32+. (2.5 mol%)NiCl2•dme (5 mol%)
dtbbpy (5 mol%)
hv, r.t.
R1
R2
SiO
O
2
HNR"R""2
BrR
R1
R2 R
Ar
Ar
Ar:
OMe 77% 94%
O
O Ar79%
Ru(bpy)32+. (2.5 mol%)NiCl2•dme (5 mol%)
dtbbpy (5 mol%)
hv, r.t.Si
O
O
2
H3N H2N (Het)Ar(Het)ArBr
N
N
R
CN
R
CF3 NH
OR
NH
R
NNBoc
RR
OH
89% 81% 75% 87%
53%85%
Molander’swork
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Nature,2015,524,330—334JACS,2015,137,9531—9534Org.LeB.2016,18,876—879JACS,2016,138,1760—1763Science,2016,DOI:10.1126/science.aag0209
PhotoredoxCatalysisandNickel:SelectedC-XbondformaAon Br
R HOR1
[Ir[dF(CF3)ppy]2(dtbbpy)]PF6 (1 mol%)NiCl2(dtbbpy) (5 mol%)quinuclidine, K2CO3,
34 W blue LEDs
RO
R1
62-96% yield36 examples
Dual photoredox Ni-catalyzed C-O crossing-coupling
BrR
[Ir[dF(CF3)ppy]2(dtbbpy)]PF6 (0.02 mol%)NiCl2(glyme) (5 mol%)
DABCO34 W blue LEDs
RN
R1
60-96% yield27 examples
Dual photoredox Ni-catalyzed C-N crossing-coupling
HNR1
R2
R2
IR
[Ir[dF(CF3)ppy]2(dtbbpy)]PF6 (2 mol%)NiCl2(glyme) (10 mol%)
pyridine34 W blue LEDs
R
SR1
30-97% yield28 examples
Dual photoredox Ni-catalyzed C-S crossing-coupling (Johannes and Oderinde)
HSR1
BrR
[Ru(bpy)3](PF6)2 (2 mol%)NiCl2(glyme) (5 mol%)
[(CH3)2CHCH2Si(cat)2][NH2(i-Pr)2]34 W blue LEDs
R
SR1
52-98% yield43 examples
Dual photoredox Ni-catalyzed C-S crossing-coupling (Molander)
HSR1
RI [Ru(bpy)3](PF6)2 (1 mol%)
Ni(cod)2 (15 mol%)IPr (15 mol%), Et3N
34 W blue LEDs28-97% yield17 examples
Dual photoredox Ni-catalyzed synthesis of indolines (Jamison)
NHAc R1
RNAc
R1
Ni(III)LnROBr
Ar
Ni(II)LnROAr
intermediate
IrIII
N
NN
N
t-Bu
t-Bu
F3C F
F
F
FF3C
[Ir[(dF(CF3)ppy]2(dtbbpy)]+
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Chem.Rev.2011,111,1846JACS,2014,136,13606—13609JACS,2015,137,11938—11941
O O
OTransition MetalCO2-Extrusion
Recombination
OTsuji-Saeguse CO2-Extrusion-Recombination: Enolate Allylation
NR
O
OPd(PPh3)4 (5 mol%)
[Ir(dF(CF3)ppy]2(dtbby)]PF6 (1 mol%)
blue LEDs NR
28-83% yield23 examples
Tunge - Photoredox Pd-catalyzed decarboxylative allylation
XO
O R
NiCl2(glyme) (5 mol%)4,4'-dOMebpy (5 mol%)
[Ir(dF(CF3)ppy]2(dtbby)]PF6 (1 mol%)
blue LEDs XR
32-86% yield30 examples
MacMillian - Photoreox Ni-catalyzed CO2 extrusion recombination
O Oanhydride (formed in situ)
PhotoredoxCatalysisandNickel:CO2Extrusion-RecombinaAon
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:JACS,2015,137,11938—11941
GeneralMechanismofCO2Extrusion-RecombinaAon
NO
O
OMe
Boc
Ni0Ln
Ni(II)O Ln
OMe
ONBoc
Ni(III) Ln
OMe
NBoc
CO2
Ni(I)Ln
NOBoc
Me
e−
Ir(III)
*Ir(III)Ir(II)
e−
visiblelight
-CO2recombination
PhotoredoxCatalyticCycle
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
SelectedexamplesofCO2Extrusion-RecombinaAon
NOBoc
PhN
OBoc
CNN
OBocN
OBoc
OMe
86% 83% 82% 72%
NC2H4Ph
OBocN
Ph
C2H4Ph
O
H
BocN
CyC2H4Ph
O
H
Boc76% 55% 58%
NOBoc
ONiL2
O
decarboxylation
NOBoc
O L2NiCO2
ringopening
NOBoc
O L2NiCO2
NOBoc
ONiL2
O
carbonylation
Ref:JACS,2015,137,11938—11941
ProposedMechanismBasedonCyclopropyl13C-labelingStudies
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Yoonetal,JACS,2008,130,12886—12887JASC,2011,133,1162—1164
Ru(bpy)32+
*Ru(bpy)32+
oxidant
Ru(bpy)3+
reductantSET
PhotoredoxCatalyticCycle
SET
visiblelight
i-Pr2NEt
i-Pr2NEt
Ph
O O
R
Li
Ph
O O
R
Li
H H
O
Ph
O
R
Lii-Pr2NEt
H H
O
Ph
O
R
[2+2] cycloproduct
Ar
O
R[Ru(byp)3]Cl2 (2.5 mol%)
La(OTf)3, TMEDA
23 W CFLH
RO
Ar
(a) Yoon - Photoredox Lewis acid-catalyzed [3+2] cycloadditions
R
O
Ar
[Ru(byp)3](PF6)2 (5 mol%)Sm(OTf)3, i-Pr2NEt
blue LEDs
55-86% yield16 examples
ORAr
ROH
Ar
40-84% yield10 examples
(b) Xia - Photoredox Lewis acid-catalyzed reductive cyclization
(c) Yoon - Photoredox Lewis acid-catalyzed hetero-Diels Alder
Ph
OO
R
[Ru(byp)3]Cl2 (5 mol%)LiBF4, i-Pr2NEt
200 W W-filament bulb
O RH
Ph
O
H
5-86% yield14 examples
(d) Yoon - Photoredox Lewis acid-catalyzed [2+2] cycloadditions
PhotoredoxCatalysisandLewisAcid:
TheradicalintermediatecouldbestabilizedbytheLewisacid=>suppressingback-electrontransfer
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:JACS,2015,137,11948—11941
H
O
CNBrNH
NMeO
Me t-Bu(20 mol%)
photoredox catalyst (0.5 mol%),2,6-lutidine,visible light
H
O
CN
OO O
O
1) NaBH4, (0 oC)
2) NaOH, reflux86%, 2 steps
OO
O
O
LDA, HMPA, -78 oC
OMe
OMeBr
OO
O
O
OMe
OMe
80% (4 steps)(—)-bursehernin>30:1 dr, 94% ee
ApplicaAons:
N
OO
OH
Boc
Cl
O
O±e Ni
N
OO
Boc
O
68% yield
1)
F
OMe
MgBr
2) 4M HCl in dioxane NH
O HOH
O
MeO
F
•HCl
(±)-edivoxetine•HCl
PhotoredoxNi-CatalyzedCO2extrusion-recombinaAon:
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ref:Acc.Chem.Res.DOI:10.1021/acs.accounts.6b00270
GeneralSet-upsforBatchandFlowPhotocatalyAcReacAons
MayLabDualPhotoredoxCatalysisinOrganicChemistryPo-AnChen10/18/2016
Ideas
NNHTsbase, photocatalyst
O
X
2
R
NNHTs base, photocatalyst
Au
N2BF4
Rn
base, photocatalyst
Au
Thankyouforyoura^enFon