Visible Light-Induced Reductive Photoredox Catalysis in Organic Synthesis
Visible-Light-Mediated Organic Photoredox Catalysis in...
Transcript of Visible-Light-Mediated Organic Photoredox Catalysis in...
X
YPSX Y +
Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of Alkenes
Reporter: Leifeng Wang Prof. Huang Group Meeting
August 22th 2016
Literature Report
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
CN
CN
CN
CN
O
DCB
DCA
BP
CN
CN
DCN
= 291 nm
= 325 nm
= 422 nm
Cyanoarenes Benzophenones
= 335 nmO
Me2N NMe2MK
= 365 nmO
FLN= 377 nmO
XXO: X=O
= 340 nm
TXO: X=S= 360 nm
Quinones
O
OAQ= 326 nm
CN
CN
Cl
Cl
O
O
DDQ
∼377 nm
Cl
Cl
Cl
Cl
O
O
TCBQ
= 450nm
Organo-photocatalyst : What is?
R
NMe
Acr-Me+
Ph-Acr-Me+: = 424nm
Mes-Acr-Me+: = 425nm
NR′
NR
RN
R
R
AOH+: = 495nm R= Me, R'=H
AcrF+: = 470nm R= H, R'=Me
= 470nm R= H, R'=HPFH+:
NN
O
O
O
O
RR
PDI: R=H
PDI-a: R=2,6-diisopropylphenyl
PDI-b: R=2,5-di-tert-butylphenyl
S
NPh
PTh:= 315 nm
S
N
N N
MB+: = 650nm
NN MeMe
DAP2+
O
CO2HY
HOX X
O
Y
ZZ
Z
Z
Fluorescein: = 491nm X,Y,Z=H
Eosin Y: = 533nm X,Y=Br, Z=H
Rose Bengal: = 549nm X,Y=I, Z=Cl
O
CO2R''Y
N N
Y
R
R'
Rhodamine B: = 550nm
Rhodomine 6G: = 550nm
R'=H,Y=Me, R,R''=Et
R'',Y=I, R,R'=Et
N
R
Me
NMQ+:< 300 nm
= 329 nmQuCN+:
X
R
R R
X=O or S, R=H or OMe
Acridiniums
Thiazines
Xanthenes
Pyryliums
Quinoloniums
Organo-photocatalyst : What is?
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
+hv
S0
S1
or -hv
or -hv
v0
vn
T1
ISCIdeal features
for S1:high φflong τf
Ideal featuresfor T1:
high φISClong τT
non-radiativeradiative
S0: ground state singlet S1: excited state singlet ISC: intersystem crossing
τf: lifetime of fluorescence
φf: quantum yield of fluorescence
T1→S0:spin forbidden
T1 states tend to be the
longest-lived
Photophysical Processes
750 nm red
380 nm/violet
Oxidative and Reductive Quenching Cycles of a Photoredox Catalyst
PS∗
oxidative quenching
sub or [Red] sub or [Ox]
reductive quenching
sub or [Red]
PS
PS
sub or [Ox]sub or [Red]
PS
sub or [Red]sub or [Ox]
sub or [Ox]
turnover
turnover
PS is an excited state reductant
PS is an excited state oxidant
HOMO
LUMO +
HOMO
LUMO
ET
HOMO
LUMO
HOMO
LUMO
1PS∗ sub
subPS
HOMO
LUMO +
HOMO
LUMO
cage escape
1
HOMO
LUMO +
HOMO
LUMO
ET
HOMO
LUMO
HOMO
LUMO
3PS∗ sub
subPS
HOMO
LUMO +
HOMO
LUMO
3
BETcage escapeBET
free ions ground state reactants
subPS PS sub
Singlet or Triplet Excited States: Does It Matter?
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
PS∗
PS
PS
H X
PS
PS
PS∗
Ox.Quench.
Red.Quench.
[-e-]
[Ox]
[Ox]
[Ox]
[Ox]
PS∗
PS
PS
X H
PS
PS
PS∗ Ox.Quench.
Red.Quench.
[+e-]
[Red]
[Red]
hv
hv
hv
hv
[Red]
[Red]
Net Oxidative Net Reductive
+ X Y
PS PS
PS
PS
[±-e
- ]Ox.Quench.
Red.Quench.PS∗
hv hvPS∗
XY
Net Redox-Neutral
Net Redox Outcomes for Photoredox Transformations
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
DCA (20 mol %)λ = 405 nm
PPh3(0.6 eq.)DMF/i-PrOH/H2O
CN
CN
DCA= 422 nm
68% 73% 61%
YMe
O
n
MeO
Y
n
Me
O
CO2Me Me
ONC
Me
O
CN
CO2EtMe
O DCA (20 mol %)λ = 405 nm
condition
MeO
EtO2C
H
H
O
Me
H
+
O
Y
DCA (20 mol %)λ = 405 nm
PPh3(0.6 eq.)DMF/i-PrOH/H2O
O
H H
Y Y = CO2Et: 84%Y = CN: 72%
condition A: PPh3(0.6 eq.), DMF/i-PrOH/H2Ocondition B: 1,5-dimethoxynaphatene(15 mol%), ascorbic acid(2.6 equiv),DMF/i-PrOH/H2O
76%
<20%
14%1.6:1 cis:trans
70%1.6:1 cis:trans
Selected Products
A:
B:
C:
Reductive Cyclizations of Unsaturated Enones
Ghorai, M. : Tetrahedron Lett. 1994, 35, 7837
CO2EtMe
O
CO2EtMe
OH
Me
OEtO2C
DCA*
DCADCA
H2O
PPh3
PPh3
H2O
-e-O=PPh3hv
+e-+H+
Me
OEtO2C
Mechanism:condition A
CO2EtMe
O
CO2EtMe
OH
Me
OEtO2C
DCA*
DCADCA
H2O
DMN
DMNhv
+e-+H+
Me
OEtO2C
Mechanism:condition B
2 HA-
A + HA- + H+
Reductive Cyclizations of Unsaturated Enones
X
R1
R2Me3SiO DCA (20 mol %)
λ = 419 nm
MeCN/i-PrOHor MeCN X
R1
R2O H
H
CN
CN
DCA= 422 nm
O H
H
O H
H
O H
H
Me
H
H
O
O H
H
H
H
25% 19%1:1 dr
51%1.1:1 dr
20%2.3:1 dr
Me3SiO
O H
H
Me3SiO
OH
HH
O H
H
DCA*DCA
DCA
hv
Mechanism -SiMe3-
6-endo-trig
selected products:
Oxidative Cyclization of Unsaturated Silyl Enol Ethers
Fu, W.-F.: Eur. J. Org. Chem. 1998, 1998, 1583.
OHR1 R2
O+ BPSS(20-30 mol%)
i-PrOH/H2O, solarH
R
R1 R2
OOHR
O
NaO3S SO3NaBPSS
(mixture of 3,3' and 4,4' isomers)
O
OH
MeMe n-Pr
O
O
MeMe CO2H O
OO
Hn-Pr
66% 83% 40%
OHH
R
OHR R1 R2
O
R1 R2
OOHR
BPSS* BPSSH
BPSS
R1 R2
OOHR
Mechamism
Selected Products
solar
Radical Conjugate Addition Reactions in Flowwith Solar Irradiation
Fagnoni, M.: Green Chem.
2009, 11, 1653
R + SONaF3C
O
Mes-Acr-Me+ (5 mol%), MTS (20 mol%)
CHCl3/TFE (9:1), 455 nm blue LEDsCF3
R
H
SH
CO2MeMTS
HOH
CF3 BzO CF3 PhthN CF3
PhCF3
OH
H Me H MeCF3
Me
Me
Ph2t-BuSiO
CF3
OH4-OMe-Ph Me
CF3
4-OMe-PhMe
CF3
4-Cl-Ph50% 69% 66% 69%
51% 67% 64% 56%
(1-3 equiv.) 25-74% yieldsslected products
SOF3C
OS
OF3C
OCF3
R
RCF3
RCF3
H
Mes-Acr-Me+ Mes-Acr-Me
Mes-Acr-Me+
∗CO2Me
S
CO2Me
S
CO2Me
SH
OH
CF3
TFEhv
+H+Mechanism
-SO2
HAT
Hydrotrifluoromethylation of Alkenes Using the Langlois Reagent
Nicewicz: Chem. Sci. 2013, 4, 3160
R +I
O
CF3
MB-Cl (2 mol%), DBU (2 equiv)
λ = White LEDs
RCF3
Me CF3 CF3HO CF3BzOO
Me
CF3MeH
H
67% 48% 83% 40%
9
S
N
N N
Cl
MB-Cl
Selected Products:
O
IO
CF3
O
IO
CF3
O
CF3R
RCF3
RCF3
MB+
MB+
MB
∗
IO
O
DBU
DBU
DBU
N
N-H+
Mechanism
Olefin Hydrotrifluoromethylation
Scaiano, J. C: ACS Catal. 2014, 4, 2530
R1
R2
R1
R2
+ p-MeO-TPT (3 mol%), 0.5 eq. ER
MeCN, λ = 450 nmR2
R1 R1
R2
O
PMP
PMP PMP
BF4-
= 470nmp-MeO-TPT
Me Me
MeO OMeMeO OMe
MeO OMeMe Me
MeO OMe
MeO
OMe MeO
OMe
N NCBz CBz
H
H
H
H
50%(±)-magnosalin
73%83%54%
O
PMP
PMP PMP
BF4-
Ar
R
Ar
R
Ar
R+
Ar
R R
Ar Ar
R R
Ar
ERER
*
O
PMP
PMP PMP O
PMP
PMP PMP
BF4-
λ = 450 nm
Mechanism
selected products:
Nicewicz:J. Am. Chem. Soc. 2015, 137, 7580
Styrene Cyclodimerization
RBF3
K
+
R1
R2
EWG Mes-Acr-MeClO4 (2 mol%)Acetone/MeOH (1:1)
λ = 425 nm (blue LEDs) R1
R2
EWGR
MeCO2Et
CO2EtAd
Cyc Me
CO2BnO
Cyc
MeCO2Et
CO2Etn-Bu
94% 88% 61% 38%
Selected Products:
RCO2H +
CO2EtEtO2C
Me
Mes-Acr-MeClO4 (2 mol%)Na2CO3 (0.1 equiv.)
MeOHλ = 425 nm (blue LEDs)
MeCO2Et
CO2EtR
1.2 equiv
MeCO2Et
CO2EttBu
MeCO2Et
CO2EtAd
MeCO2Et
CO2EtCy
81% 86% 40%
1.2 equiv
Selected Products:
Deborylative and Decarboxylative Radical Conjugate Addition Reactions
Akita, M.: RSC Adv. 2015, 5, 21297
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
CbzNHOH
R
R1R2
R3H
+
RB-Na2 (3 mol%)pyridine (10 mol%)
MeCN, Airλ ~ 11 w fluorescent
N
R3
R2Cbz
OH
R R1
NPhCbz
OH
NCbz
OHn-Pent
NCbz
OH
Me
O NH2
NCbz
OHn-Pr
n-Pr
78% 44% (4:1 E/Z)
70% (4:1 E/Z)
81%
Selected Products:
CbzNHOH
CbzNHOH
CbzNHO
CbzNO
Ph
H
NPhCbz
OH
RB2-
RB2-
RB•3-∗
O2
O2HO2 H2O2 Nitroso-Ene
Mechanism
O
CO2NaI
NaOI I
O
I
ClCl
Cl
Cl
RB-Na2
Nitroso-Ene Reaction Enabled by PET
Tan C.H.: ChemCatChem 2013, 5, 235
R
Cat. (5 mol%), TEMPO (20 mol%)
amine (1,25-2 equiv), DCE, 1 atm O2λ = 455 nm (blue LEDs)
R
NR R
N
Mes
Ph
tBu tBu
Cat. = Mes-(tBu)2Acr-PhBF4
OMe
NN
NN
N
Me
N
Me
NN
Me Me
OMe
NNN
OMe
NH2
OMe
NH2
ClN
N
NH2
Me
88% 7:1 p:o
43% 82% 71% 3.5:1 p:o
using 4 equiv. amine = NH2CO2NH4
59% 1.6:1 p:o
33% 61%
selected products:
R R
catalyst+* catalyst
catalyst+
HN
N
HNN
RNN
R
NN
HH
OO
TEMPO
TEMPO-H
O2
O2
HOO--HOO
path A
path B
Mechanism
Aryl C−H Amination
Nicewicz: Science
2015, 349, 1326
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
SAr
O ONa+
RAr1
R1
RAr1
R1
SAr
O OEY-Na2 (10 mol%)PhNO2 (1 equiv)
DMF/H2O (3:1), 40 °Cλ = Green LED11-99% yields
S
F
O O
N
SPh
EtO
OEtO
O OS
R
O O
R = H, 99%, R = Me, 79%R = OMe, 51%, R = F, 79%54% 11%
Selected Products:
(3 equiv)
EY2-
EY2-
EY•3-∗
SAr
O O SAr
O OR Ar1
R1
RAr1
R1
SAr
O O
PhNO2
PhNO2
RAr1
R1
SAr
O OPhNH2Mechanism
hv
O
CO2NaBr
NaOBr Br
O
Br
EY-Na2
Vinyl C−H Sulfonylation via PET-Generated Sulfinyl Radicals
Burkhard K.:Adv. Synth. Catal. 2015, 357, 2050
ArEYH2, NH4SCN (1 equiv.), MeCN, Air
λ (Green LED)74-96% yields
OS
Ar
NH
O
S
NH O
S
NH
MeOO
S
NH
O2N
92% 96% 74%
Selected Products:
ArAr
SCN
Ar
SCNOO
Ar
SCNO
Eosin Y Eosin Y
Eosin Y
NCS NCS
O2
O2
+ NH4
Ar
SOH
N
O
SAr
NH
O2
NH3 + O2∗
Mechanism
hv
O
CO2HBr
HOBr Br
O
Br
Eosin Y
2-Imino-1,3-Oxathiolanes by Difunctionalization of Styrenes
Yadav, S.: Green Chem. 2015, 17, 3515
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
R
RR
R
Mes-Acr-MeClO4 (20 mol%)
CD3CN, 1 atm O2λ > 430 nm
O OR RR R R R
O
Me
MeMe
Me
Ph
PhPh
Ph
O OMe MeMe Me
O OPh PhPh Ph
Me Me
O
Ph Ph
O
+
~30%
~20%
~10%
~70%
reactants products
R
RR
R
O2
Proposed Key Step
R
R
Mes-Acr-MeClO4, O2, hv
R
R
+
O
O
OO
Tetrasubstituted Alkene Oxygenation
Fukuzumi, S:J. Am. Chem. Soc. 2004, 126, 15999
RDDQ, t-BuNO(5 mol%), H2O(17 eq.), MeCN, O2
λ > 390 nm
R
OH
CN
CN
Cl
Cl
O
ODDQ∼377 nm
OH
93%
OHF
34%p-:o-:i- = 4.2:1:2.5
OHCl
34%p-:o- = 4.6:1
OHBr
14%p-:o- = 3.9:1
HO HOH
DDQ*
O
O
CN
CN
Cl
Cl
OH
O
CN
CN
Cl
Cl
OH
OH
CN
CN
Cl
ClDDQ
t-BuNOO2
λ> 390 nmDDQ DDQH DDQH2
Mechanism
Selected Products:
C−H Hydroxylation of Benzene and Halobenzenes
Fuzukimi, S: J. Am. Chem. Soc. 2013, 135, 5368.
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes C-N bond formation C-C bond formation C-S bond formation C-O bond formation III: Summary
PRCC Reactions
R
R
Nuc
via:
O
O
R
NRH
BnO
N PG
OH
R
R
O
OH
R
R
O
H
R
R
R
H
O R
R
H
O R
O
R
H HN
SR
O
O
R
HN X
X
R
HF
R
HCl
R
H
O PO
OO
R
H
O SO
OO
Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions
Nicewicz Group
Me
Ph+
OHNPG
Ph
DCM, 455 nm LEDs NO
BnPh
MePG
ON
BnPh
Me
PG+
PG = Ms, Ts, Ns, Tf
R
R
R1NH
R2
O R3
Mes-Acr-MeBF4 (2.5 mol%), (PhS)2 (10 mol%)
DCE, 455 nm LEDs ON
R3
R2R
R
H
R1
53-95% up to 2:1 dr
OMe
Me n Cl
OHO
1) Mes-Acr-Me+ (2.5 mol%), (PhS)2 (10 mol%)
2) RuO4/NaIO43) K2CO3, NEt3, i-PrOH
OO
HO2C
Me nn = 3, (±) methylenolactocin 16%
n = 11, (±) protolichesterinic acid 37%
RR1
NH
R2
S R3
Mes-Acr-MeBF4 (2.5 mol%), (PhS)2 (10 mol%)4-MeO-PhSH (20 mol%)
DCE, 455 nm LEDs SN
R3
R2
RR1
60-80% up to 4:1 dr
H
Mes-Acr-Ph+ (5 mol%), 4-MeO-PhSH (30 mol%)2,6-lutidine (20 mol%)
Highlights of Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions
from Nicewicz Group
Org. Lett. 2015, 17, 1316 Chem. Sci. 2015, 6, 270 Org. Lett. 2014, 16, 4810
R RR
XR'
RX
R'
H
Mes-Acr+*
Mes-Acr+
Mes-Acr PhS
PhS
PhS-H
PhSSPh
R'-X-H-H+
hv hv
X H -H+
RX
RX
R
HHAT
PRCC
HATcycle
PETcycle
NMe
Me
Me
Me
X
NMe
Me
Me
Me
X
Bulky Mes-group blocksaddition at 9-position
Mes-Acr-Me+
Mes-Acr
tBu OH
O+
NMe
NaOH, MeCN/H2O, O2
λ = 358 nm N
tBu
Me
Proposed Mechanism for Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions
Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation
III: Summary
R
Cyclo-additions
AtomTransfer
Cyclizations
C-HFunctionalizations
Hydro-functionalizations
BondCleavageReactions
C-C
C-N C-O
C-S
Summary
1) Site specificity and functionalization of stronger C−H bonds present new challenges 2) Methods for controlling enantioselectivity are scarce 3) Applications of organic photoredox catalysis to natural product synthesis are just
starting to occur 4) Highly reducing catalysts and more robust chromophores are always in demand
Challenges Remain:
Thank You for Your Kind Attention!
What Can We Do
Intramolecular
X
R1
R2Me3SiO DCA (20 mol %)
λ = 419 nm
MeCN/i-PrOHor MeCN X
R1
R2O H
H
CN
CN
DCA= 422 nm
> 650 nm
PSOSiMe3
R+
PS (x mol %)blue/green LEDs
solvent/rt
O
n n
R
Intermolecular
R
R
Nuc
via:
O
O
R
NRH
BnO
N PG
OH
R
R
O
OH
R
R
O
H
R
R
R
H
O R
R
H
O R
O
R
H HN
SR
O
O
R
HN X
X
R
HF
R
HCl
R
H
O PO
OO
R
H
O SO
OO
Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions
Nuc = Carbon & Organic Photoredox Catalysis/Transition Metal Catalysis
R1
OH R3
+
PS (x mol %)/additiveblue/green LEDs
solvent/rt R1
OR3
> 650 nm
PS
R2 R2
X+
R
PS (x mol %)/TMblue/green LEDs R
Nuc = Carbon
Anti-Markovnikov Alkene Hydrofunctionalization Reactions
> 650 nm
PS
R Nuc
RadicalAcceptor RA
RNuc
RA
RA = O2
RA = Togni ReagentRA = AlkeneRA = Aryl ......
Difuctionalization of Alkenes
R+
PS (x mol %)/O2blue/green LEDs
solvent/rtCN-
R
OCN
Organic Photoredox Catalysis/Transition Metal Catalysis
R
Nuc RNuc
Ni(0)
RNuc
Ni(I)
Ar X
RNuc
Ni(III)Ar X
RNuc
Ar
Ni(I) X
Ni(0)