main-group elements (bi) in catalysis for organic synthesis · 18/03/2020 · the application of...
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Main-group Elements (Bi) in Catalysis for Organic Synthesis
Xiaheng ZhangMacMillan Group Meeting
March 18th 2020
XR
LX
R
L
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Mechanisms of Activation Mode for Main-group Elements
■ Activation mode of transition metal elements
XR
LX
R
L
M
! donation into empty d-orbital
M
" donation from d-orbital into "∗-orbital
! donation into empty p-orbital " donation from p-orbital into "∗-orbital
■ Activation mode of main-group elements
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Activation of Small Molecules by Main-group Elements
Frustrated Lewis pairs activation
Stephan, D. W. et al. Science 2006, 314, 1124.
Activation of H2 by carbenes
iPr2N
Mes2P B
F4
H2 25 oC
> 100 oCMes2P B
F4
H H
Stephan, D. W. et al. Science 2016, 354, aaf7229.
Me
MeMe H2 35
oCiPr2N
Me
MeMe
Frey, G. D.; Lavallo, V.; Donnadieu, B.; Schoeller, W. W.; Bertrand, G. Science 2007, 316, 439.
H H
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Catalysis Enabled by Main-group Elements
Frustrated Lewis pairs catalyzed hydrogenation
Chernichenko,K.;Madaraśz,A.;Paṕai,I.;Nieger,M.;Leskela,̈ M.;Repo,T. Nat. Chem. 2013, 5, 718.
FLP catalyzed C-H activation
H2 FLP (5 mol%)
Leǵare,́M.-A.;Courtemanche,M.-A.;Rochette,É.;Fontaine,F.-G. Science 2015, 349, 513.
BuPh
Bu
Ph
H
H
N
B(C6F5)2
Me
Me
FLP (Cat.)
N
Me
HN
Me
BpinH-Bpin FLP (2.5 mol%)N
BH2
R
R
FLP (Cat.)
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Catalysis Enabled by Main-group Elements
C-H silylation catalyzed by alkali metal catalyst
Toutov, A. A.; Liu, W.-B.; Betz, K. N.; Fedorov, A.; Stoltz, B. M.; Grubbs, R. H. Nature 2015, 518, 80.
Imine hydrogenation catalyzed by alkaline earth metal catalyst
KOt-Bu (20 mol%)
Harder, S. et. al. Nat. Catal. 2018, 1, 40.
H2 Ca (10 mol%)
N
Me
H
Et3SiHN
Me
SiEt3
MeMe
NMe
MeMe
NMe
H
H
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Main-group Elements (Bi) in Catalysis for Organic Synthesis
■ The facts of bismuth
■ Synthesis of organobismuthines
■ The application of organobismuthines in organic synthesis
■ Redox chemistry of bismuth
Outline
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Why do people care about bismuth catalysis
Bi
Peptobismol OTC
stomach disorders
■ naturally abundant
■ ‘green element’ even less toxic than NaCl■ widely used in industry, antibiotics, radiopaque bone cements, polymers
electron configuration: 4f145d106s26p3
common oxidation state: +1, +3, +5
Can we discover new reactivity that is unique to bismuth catalysis?
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Main-group Elements (Bi) in Catalysis for Organic Synthesis
■ The facts of bismuth
■ Synthesis of organobismuthines
■ The application of organobismuthines in organic synthesis
■ Redox chemistry of bismuth
Outline
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Synthesis of organobismuthines
■ Synthesis of trivalent organobismuthines
BiCl3ArMgBr, ArLi or ArBr, CoBr2, Zn
BiAr3
BiCl3 (0.5 eq)BiAr2Cl
BiCl3 (2.0 eq)BiArCl2
■ Synthesis of highly functionalized trivalent organobismuthines
Gagnon, A. et. al. J. Org. Chem. 2016, 81, 5401.
Bi
OH
3
NaBH4 Bi
OH
3
97% yield
BrCH2CO2EtPPh3Bi 3
CO2Et
80% yield
Bi3
Me
99% yield
HO
MeMgBr Bi 3
82% yield
Ph3PCH3It-BuOK
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Synthesis of organobismuthines
■ Synthesis of pentavalent organobismuthines
Michaelis, A. Ber. Dtsch. Chem. Ges. 1887, 20, 52.Barton, D. H. R.; Finet, J.-P. Pure Appl. Chem. 1987, 59, 937.
Bi3
Br2
Cl2 or PhICl2
Bi3
Cl
Cl
NaF or AgFBi
3
F
F
K2CO3O3CBi3
RCO2H, H2O2Bi
ROCO
ROCO 5Bi
3
Br
Br
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Main-group Elements (Bi) in Catalysis for Organic Synthesis
■ The facts of bismuth
■ Synthesis of organobismuthines
■ The application of organobismuthines in organic synthesis
■ Redox chemistry of bismuth
Outline
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Organobismuth as arylation reagents
■ The first arylation reaction using organobismuthines
75% yield
N
MeO
HO NPh3BiCO3
DCMN
MeO
ON
N
MeO
ON
Ph
Barton, D. H. R.; Lester, D. J.; Motherwell, W. B.; Papoula, M. T. B. J. Chem. Soc., Chem. Commun. 1980, 246.
■ The first C-arylation of phenols organobismuthines
OH Ph3BiCO3
TMG
OH
Ph
76% yield
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Organobismuth as arylation reagents
■ O-arylation and C-arylation controlled by condition
90% yield 90% yield
91% yield 57% yield
Me
Me
O
Me
BiPh3X
Me
Me
O
Me
Ph
Me
Me
O
MePh
Ph4BiO2CCF3
TMG
basic conditions
Ph4BiO2CCF3
Cl3CCO2H
acidic or neutral conditions
OH
PhOPh
O
PhCO2Et
OPh
CO2Et
Me
Me
OPhMe
Me
OPh
72% yield 58% yield
Barton, D. H. R. et. al. J. Chem. Soc., Chem. Commun. 1980, 827. Barton, D. H. R. et. al. J. Chem. Soc., Chem. Commun. 1981, 503.
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Organobismuth as arylation reagents
■ O-arylation of alcohols, diols, aminoalcohols
73% yield
Me
MeOH Ph4BiO2CCF3 or Ph3Bi(OAc)2
DCM or toluene
David, S.; Thieffry, A. J. Org. Chem. 1983, 48, 441. Barton, D. H. R. et. al. J. Chem. Soc., Chem. Commun. 1986, 65.
Me
MeO
Ph
tBu
OPh
OH
OPh
OHMe
88% yield
PhHNOH
51% yield
HO OPhMe Me
99% yield
MeOOPh
86% yield
PhPh
O
OPh
88% yield
HOOPh
80% yield
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Organobismuth as arylation reagents
■ O-arylation of tertiary alcohols via Cu catalysis
OH
Me
Me Ph3Bi(OAc)2, Cu(OAc)2, Cy2NMe, O2
DCM or toluene
Ikegai, K.; Fukumoto, K.; Mukaiyama, T. Chem. Lett. 2006, 35, 612. Mukaiyama, T.; Sakurai, N.; Ikegai, K. Chem. Lett. 2006, 35, 1140.
89% yield
EtO2C
O
Me
Me
EtO2CPh
O
Me
Me
EtO2CPh
89% yield
OMe
EtO2CPh
Ph
94% yield
O
Me
EtPh
88% yield
OPh
BnN
Ph
87% yield
O
Me
Me
MePh
50% yield
O
Me
MePhTBSO
O
N
-
Organobismuth as arylation reagents
■ Cu catalyzed arylation of N, S-nucleophiles
Nu
Me
Me Ph3Bi(OAc)2 or Ar3Bi, Cu(OAc)2, O2
Gagnon, A. et. al. Synthesis 2017, 49, 1707.
96% yield
Nu
Me
MePh
HN
Ph
80% yield 91% yield
Me
Me
HN
OBn
Ph
Ph
O
O NH
HN
O
PhtBu
N
MeO2C
Ph-pMe
87% yield
N
N
Ph
87% yield
N N
N
Ph
60% yield
N NN
N
Ph
87% yield
Ph
S
Ph
84% yield
MeO
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Organobismuth as arylation reagents
■ Cu catalyzed arylation of N, S-nucleophiles
Nu
Me
Me Ph3Bi(OAc)2 or Ar3Bi, Cu(OAc)2, O2
Gagnon, A. et. al. Synthesis 2017, 49, 1707.
96% yield
Nu
Me
MePh
HN
Ph
80% yield 91% yield
Me
Me
HN
OBn
Ph
Ph
O
O NH
HN
O
PhtBu
N
MeO2C
Ph-pMe
87% yield
N
N
Ph
87% yield
N N
N
Ph
60% yield
N NN
N
Ph
87% yield
Ph
O
NMe
52% yield
Me3Bi
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Cross-coupling using organobismuth
Pd
Rh
CO2EtPh3Bi
CO2EtPh
Pd
Ph3BiN
N Cl
FGN
N Ph
FG
Pd
Ph3BiPO
Ph
EtOH P
OPh
EtOPh
Pd
c-Pr3BiN Cl
CN
N
CN
Gagnon, A.; Duplessis, M.; Alsabeh, P.; Barabé, F. J. Org. Chem. 2008, 73, 3604.
Wang, T.; Sang, S.; Liu, L.; Qiao, H.; Gao, Y.; Zhao, Y. J. Org. Chem. 2014, 79, 608.Kawamura, T.; Kikukawa, K.; Takagi, M.; Matsuda, T. Bull. Chem. Soc. Jpn. 1977, 50, 2021.
Gagnon, A. J. Org. Chem. 2016, 81, 5401.
O
Ph3Bi
O
Ph
Li, C.-J. et. al J. Am. Chem. Soc. 2001, 123, 7451.
OPh3BiCl2, PBu3
OPh
Krische, M. J. J. Am. Chem. Soc. 2004, 126, 5350.
Bi redox chemistry is unclear with rare examples
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Main-group Elements (Bi) in Catalysis for Organic Synthesis
■ The facts of bismuth
■ Synthesis of organobismuthines
■ The application of organobismuthines in organic synthesis
■ Redox chemistry of bismuth
Outline
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Bi(III)/Bi(V) redox activation
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi X B(OH)2 SO O
Bi OH
[O]OH
ortho-Arylation of phenols via Bi(III)/Bi(V) redox activation
OH
HO
iPr
Me
Liganasantibacterial, cyctotoxic
OH
CO2H
NH
N
NN
OAr
Pharmaceuticalsaplastic anemia
N
N
OH
Cl
Agrochemicalsherbicide
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Bi(III)/Bi(V) redox activation
■ Current approaches for the preparation of 2-hydroxybiaryls
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
H
OH
R
H
O
R
H, X, Li
PG, DG
H, X, Li OR
OH
R
2-hydroxybiaryls
OBiPh3XPh4BiO2CCF3
TMG
basic conditions
Ph4BiO2CCF3
Cl3CCO2H
acidic or neutral conditions
OH
Ph
OPh
■ Barton’s pioneer discovery
■ O or C arylation is highly dependent on the nature of the organobismuth and reaction conditions■ multistep synthesis of arylbismuth reagents, transfer one of the aryl groups in the organobismuth■ lack of systematic studies of mechanism which impedes practical exploration of the method
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Bi(III)/Bi(V) redox activation
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi X B(OH)2 SO O
Bi OH
[O]OH
ortho-Arylation of phenols via Bi(III)/Bi(V) redox activation
■ one-pot boron-to-bismuth transmetallation ■ commercially available starting materials■ completely prevents the formation of O-arylated products■ operates under air in non-anhydrous conditions
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Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
■ Reaction design
SO O
Bi X
SO O
Bi
B(OH)2
B-to-Bi transmetallation
mCPBA
Bi(III) to Bi(V) oxidationBi
OOH
SO
O
O
Cl
OH
phenol deprotonation
Bi
OO
SO
O
O
Cl
HO
arylated product
exocyclicaryl group
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Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi OTs SO O
Bi
B-to-Bi transmetallation
B(OH)2
(1.1 equiv.)
K2CO3 (1.2 equiv.)
PhMe/water (99/1), 60 oC, 2h
SO O
Bi F
SO OLi Li
SO OnBuLi
ArBiBr2BiBr3 Ar3Bi
■ Transmetallation to universal bismacyclic precursor
TsOH
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi OTs SO O
Bi
B(OH)2
(1.1 equiv.)
K2CO3 (1.2 equiv.)
PhMe/water (99/1), 60 oC, 2h
■ Transmetallation to universal bismacyclic precursor
>99% yield
SO O
Bi NMe2
>99% yield
SO O
Bi CN
>99% yield
SO O
Bi
F3CO
>99% yield
SO O
Bi
Me
Me
Me
>99% yield
SO O
Bi
>99% yield
SO
BiNBoc
>99% yield
SO
Bi
>99% yield
SO
BiN
O
Me
MeN
OMe
NH
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi OTs SO O
Bi
B(OH)2
(1.1 equiv.)
K2CO3 (1.2 equiv.)
■ One-pot, Bi(V)-mediated arylation of phenols and naphthols
69% yield
OH
OH
mCPBA, r.t., 10 min
OH
77% yield
OHMeO
OMe
F
59% yield
OH
F
Br
OH
Me
Me Me
89% yield
OH
87% yield
Br
OH
59% yield
OHN
93% yield
p-F
OH
90% yield
p-F
HN
N
SMe
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi OTs SO O
Bi
B(OH)2
(1.1 equiv.)
K2CO3 (1.2 equiv.)
■ One-pot, Bi(V)-mediated arylation of phenols and naphthols
OH
OH
mCPBA, r.t., 10 min
+
SO O
Bi OmCBAcOH elution
SO O
Bi OAc
B(OH)2
96%
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi OTs SO O
Bi
B(OH)2
(1.1 equiv.)
K2CO3 (1.2 equiv.), 1h
■ Mechanistic studies for the reaction
FF
SO O
Bi OH H2OS
O OBi O
S
O
O
Bi
>99%
K2CO3,PhMe/water
30 minr.t., 99%
B(OH)2
F
isolated
plausible pre-transmetallation intermediate
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
■ Reaction design
SO O
Bi X
SO O
Bi
B(OH)2
B-to-Bi transmetallation
mCPBA
Bi(III) to Bi(V) oxidationBi
OOH
SO
O
O
Cl
OH
phenol deprotonation
Bi
OO
SO
O
O
Cl
HO
arylated product
exocyclicaryl group
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi
■ Mechanistic studies for the reaction
F1) mCPBA, PhMe2) DBU
Bi
OO
SO
O
Bi
SO
O
F
F
(X-ray)
Bi(V) dimer
Bi(V) dimermCPBA
Bi
OmCBOH
SO
O
mCPBA
Bi
OmCBOmCB
SO
O
mCBA/Bi = 1.3 2NMR ratio
HO
F
PhOHPhOH
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi
■ Mechanistic studies for the reaction
F1) mCPBA, PhMe2) DBU
Bi
OO
SO
O
Bi
SO
O
F
F
(X-ray)
Bi(V) dimer
Bi(V) dimermCPBA
Bi
OmCBOH
SO
O
mCPBA
Bi
OmCBOmCB
SO
O
mCBA/Bi = 1.3 2NMR ratio
HOPhOH
Fk > 40 M-1S-1
PhOH
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi
■ Mechanistic studies for the reaction
F
d0-PhOH (5.0 eq)d5-PhOH (5.0 eq)
OH
F
mCPBA, PhMe, r.t.
kH/kD = 1.03
SO O
Bi F
OH
F
mCPBA, PhMe, r.t.
kH/kD = 0.83
OH
D
H
-
Bi(III)/Bi(V) redox activation for ortho-Arylation of phenols
Jurrat, M.;Maggi, L.;Paṕai,I.;Lewis, W.;Ball, L. T. Nat. Chem. 2020, 12, 260.
SO O
Bi
■ Mechanistic studies for the reaction
F
Bi
OmCBOH
SO
O
Bi
OmCBO
SO
O
FF
k > 40 M-1S-1k > 1.6 M-1S-1RDS
PhOH
-H2O
OH
F
PhOH, mCPBA
PhMe, r.t.
mCPBA
-
What about Bi(III)/Bi(V) redox catalysis?
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Bpin F
Bi
SON
F3C
BF4
Bi(III) (10 mol%)NaF (5.0 eq), CDCl3, 90 oC
NCl Cl
F
BF4 (1.0 eq)
90% yield
F
TMS
71% yield
F
Ph
77% yield
F
Me
55% yield
FMeO
36% yield
FCl
84% yield
FMe
Me
Br
45% yield
F
Me
F
49% yield
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Proposed mechanism for Bi(III)/Bi(V) redox catalysis
BY2F
Bi
SON
F3C
X
C-F bond formation
Bi
SON
F3C
F-X
OA
Bi
SON
F3C
PhF
X
RETM
electrophile
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Proof of concept study
Bi
SOO
Me
XeF2 (1.0 eq)
CHCl3, 0 oC
>95% isolated
Bi
SO
O
Me
F F
FBi
SOO
Me
F
X-ray
Bi
SOO
F
Me
F110 oCCDCl3
45% yieldreductive elimination
from Bi(V) center
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Ligand effect for the reductive elimination
Bi
SOO
Me
XeF2 (1.0 eq)
F
45% yield
then 110 oC
Bi
SON
F3C
Bi
SON
Me
XeF2 (1.0 eq)
F
28% yield
then 110 oC
XeF2 (1.0 eq)
F
94% yield
then 110 oC
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Kinetic analysis of the reductive elimination
Bi
SON
F3C
XeF2 (1.0 eq) F 110 oCBi
SON
F3C
F
F
R
R
R
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Mechanism study of the reductive elimination
FBi
SO
NCF3
F
F slower decay in the presence of Bu4NF
CD3Cl, 90 oC, 6hBi
SON
F3C
F
F
C-F bond R.E.
94% yield
proposed cationic intermediates
Bi
SON
F3C
PhF
FB F
F F
fast dissociation of labile BF4- ligand
CD3Cl, 60 oC, 5min
NMR, HRMS
Bi
SON
F3C
F
BF4
C-F bond R.E. F
85% yield
1.0 eq BF3·Et2OCH3Cl, -45 oC
5 min>99% yield
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Fluoropyridinium as fluorinating reagent
CD3Cl, 60 oC, 2hBi
SON
F3C
F
BF4
F
85% yield
Bi
SON
F3C
NCl Cl
F
BF4
(1.2 eq)
Bi
SO
NF3C
F
N ClCl BF4
ligand exchange
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Transmetallation of arylborone to Bi
Bi
SON
F3C
BF4
Bi
SON
F3C
Ph-B, KF, MeCN, 90 oC
B(OH)2
95% yield
Bpin
67% yield
B
72% yield
O
O
Me
Me
PhB
80% yield
OB
OB
O
Ph
Ph
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Merging element steps together for Bi(III)/Bi(V) redox catalysis
Bi
SON
F3C
BF4
Bi
SON
F3C
Ph-B, KF, MeCN, 90 oC
CD3Cl, 60 oC, 2hBi
SON
F3C
NCl Cl
F
BF4
(1.2 eq)F
85% yield
-
Fluorination of arylboron via Bi(III)/Bi(V) redox catalysis
Planas, O.; Wang, F.; Leutzsch, M.; Cornella, J. Science. 2020, 367, 313.
■ Merging element steps together for Bi(III)/Bi(V) redox catalysis
Bi
SON
F3C
BF4
Bi
SON
F3C
Ph-B, KF, MeCN, 90 oC
Bpin F
Bi
SON
F3C
BF4
Bi(III) (10 mol%)NaF (5.0 eq), CDCl3, 90 oC
NCl Cl
F
BF4 (1.0 eq)
First Bi(III)/Bi(V) redox catalysis
-
What about Bi(I)/Bi(III) redox catalysis?
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
■ Bi(I) catalyzed transfer hydrogenation
Bi(I) (1 mol%)NH3BH3 (1.0 eq), H2O (1.0 eq)
THF, 35 oCN
NPh
PhN
NPh
Ph
H
H
N
BiN
tBu
tBu
Bi(I) catalyst
N
BiN
tBu
tBu
H
H
via Bi(III) hydride
-
What about Bi(I)/Bi(III) redox catalysis?
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
■ Bi(I) catalyzed transfer hydrogenation
Bi(I) (1 mol%)NH3BH3 (1.0 eq), H2O (1.0 eq)
THF, 35 oC
97% yield
NN
PhPh
NN
PhPh
H
H
N
BiN
tBu
tBu
Bi(I) catalyst
NN
H
H
Me
Me
99% yield
NN
H
H
CF3
F3C
98% yield
NN
H
HBr
99% yield
NN
H
H
NMe2
I
98% yield
NN
H
H
Me
Me
Me
MeNN
H H
99% yield
-
Transfer hydrogenation via Bi(I)/Bi(III) redox catalysis
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
■ Bi(I) catalyzed transfer hydrogenation of nitroarenes
Bi(I) (1 mol%)NH3BH3 (1.0 eq)
dioxane, 35 oC
97% yield
N
BiN
tBu
tBu
Bi(I) catalyst
NO2 N
H
Me
OH
N
H
Me
OH
88% yield
N
H
I
OH
67% yield
N
H
OH
82% yield
N
H
OH
75% yield
N
H
OH
22% yield
N
H
OH
Me
Me
-
Transfer hydrogenation via Bi(I)/Bi(III) redox catalysis
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
Bi(I) (1 mol%)NH3BH3 (1.0 eq), H2O (1.0 eq)
THF, 35 oCN
NPh
PhN
NPh
Ph
H
H
N
BiN
tBu
tBu
H
H
via Bi(III) hydride
Effect of water
-
Transfer hydrogenation via Bi(I)/Bi(III) redox catalysis
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
Bi(I) (1 mol%)Dn-NH3BH3 (1.0 eq), D2O
THF, 35 oC
NN
PhPh
NN
PhPh
H
H
N
BiN
tBu
tBu
H
H
via Bi(III) hydride
KIE experiments
Both N-H and B-H bonds are cleaved in the rate-determining step
-
Transfer hydrogenation via Bi(I)/Bi(III) redox catalysis
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
Bi(I) (1 mol%)NH3BH3 (1.0 eq), H2O
THF, 35 oC
Competition experiment study
■ azoarenes are not participating in the RDS of this transformation
■ Bi(I) and AB are both involved in the RDS
NN
H
H
Me
Me
NN
Me
Me
Bi(I) (1 mol%)NH3BH3 (1.0 eq), H2O
THF, 35 oC
NN
H
H
F
F
NN
F
F
Product 1:1 ratio observed
-
Transfer hydrogenation via Bi(I)/Bi(III) redox catalysis
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
■ Stoichiometric study for Bi(III)—H species
PhSiH
■ Bi(I) and H2 was detected during the reaction■ proton is from hydridic sources
N
BiN
tBu
tBu
H
H
putative Bi(III) hydrideintermediate
NN
PhPh
H
H
NN
PhPh
H
H
NN
PhPhN
BiN
tBu
tBu
F
F
N
BiN
tBu
tBu
Cl
Cl
NaBH3CNN
NPh
Ph
71% yield
98% yield
-
Transfer hydrogenation via Bi(I)/Bi(III) redox catalysis
Wang, F.; Planas, O.; Cornella, J. JACS 2019, 141, 4235.
■ Mass-spectrometry study for Bi(III)—H species
N
BiN
tBu
tBu
H
H
putative Bi(III) hydrideintermediate
N
BiN
tBu
tBu
20 mol%
NH3BH3 (1.0 equiv)
ND3BD3 (1.0 equiv)
N
BiN
tBu
tBu
H
HRMS-ESI