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High-Oxidation-State Palladium Catalysis. 报告人：刘槟. 2010 年 10 月 23 日. Introduction. In 1986 , the first unequivocal trialkylpalladium(IV) complex, [PdIMe 3 (bpy)],was isolated and characterized by X-ray analysis. Acc. Chem. Res . 1992 ,25,83-90. Advantages. - PowerPoint PPT Presentation
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High-Oxidation-State Palladium Catalysis
报告人：刘槟 2010年 10月 23日
Introduction• In 1986 , the first unequivocal trialkylpalladium(IV)
complex, [PdIMe3(bpy)],was isolated and characterized by X-ray analysis.
N
N
PdCH3
CH3
CH3I
N
N
PdCH3
CH3
CH3
I H3C-CH3
N
N
PdCH3
I
Acc. Chem. Res. 1992,25,83-90
Advantages• Some advantages compared to Pd(0)/Pd(II) catalysis:
1. Pd(IV) species are often resistant to β-H elimination process
2. Pd(IV) species undergo facile reductive elimination. (like C-C bond formation)
3. Pd(II)/Pd(IV) catalyzed reactions are operationally simple and do not require the careful exclusion of air (especially O2) and moisture.
Chem. Soc. Rev., 2010, 39, 712–733
C-C CouplingR
I
+ + 2R'I + H2C CHY
Pd cat.K2CO3 , DMA
20oC , 30h
R
R'R'
CH
CHY
+
Angew. Chem., Int. Ed., 1997, 36, 119
PdoL2 I R
RPdI
L
L
R
PdI
L
LK2CO3
KI
Pd RL L
R'I
Pd RL I
L
R'
R
PdI
L
L
R'
K2CO3
KIPd RL L
R'
R'I
Pd RL I
L
R'
R'
R
PdI
L
L
R'
R'
RPdI
L
L
R'
R'
R
R'
R'
H2C CHY
CH2
CH
Y
Pd
I
LL
K2CO3
KI
R'
RR'
HCYHC
NH
Br
+
R'
I
HR R''
Pd(OAc)2tri-2-furylphosphine
Cs2CO3 , norbornene
CH3CN , 90oC , 16hn
NR
n
R'
R''
PdoL2
COOMeI
COOMeIL2Pd
PdL2I
COOMe
Cs2CO3
CsI+CsHCO3
Pd
COOMe
L L
N Br
Pd
COOMe
L Br
L
N
NPdL2X
N
COOMeL2Pd
X
Cs2CO3
CsI+CsHCO3
N
COOMe
J. AM. CHEM. SOC. 2005, 127, 13148-13149
Me
I + Ph Ph
Pd(OAc)2norbornene
K2CO3 , n-Bu4NBr82%
Me
Ph PhMe
Me
I + B(OH)2
Pd(OAc)2norbornene
K2CO3 ,DMF88%
Me
Ph Me
Me
I + R
Pd(OAc)2norbornene
K2CO3 ,DMF
Me
MePh
Chem. Soc. Rev., 2010, 39, 712–733
NH + I
BF4-
5 mol% PdII
AcOH , 25oC N
Pd(OAc)2 49% , 5minIMesPd(OAc)2 86% , 18h
NR +
I
R'
Pd(OAc)2 , PPh3
CsOAc , DMA125oC , 24h
NR
R'
(a) Pd0/II Catalytic Cycle
Pd0
+
Ar I
PR3
PdIIR3P
R3P
Ar
I
Electron Rich
SLOW
ElectrophilicPalladation
NH
PdIIR3P
R3P
Ar
N
NAr
-Pd0
(b) PdII/IV Catalytic Cycle
PdII(OAc)2
ElectronDeficient
FASTER?
ElectrophilicPalladation
NH
PdII OAc
N
[Ar2I]BF4 PdII OAc
NAr
-Pd0
Pd0/II versus Proposed PdII/IV Mechanism for Indole Arylation
J. AM. CHEM. SOC. 2006, 128, 4972-4973
carbon-carbon bond formation from unactivated alkyl C-H bond
N
NH
O
Me
+ p-MeOC6H4I
5 mol% Pd(OAc)2AgOAc
150oC , no solvent
N
NH
O
Me
MeO
J. AM. CHEM. SOC. 2005, 127, 13154-13155
N
NHBn
OPd(OAc)2
N
N
O
PdBnAcO 2
1. ArI2. C-H activation
OR1. C-H activation2. ArI
N
N
O
PdAr
IL
red. elimination
protonationligand exchange
N
HN
O Ar
Mechanistic Considerations
N R
Ph2Si(OH)Me
Pd(OAc)2 (cat.)Cu(OAc)2 (oxidant)
DMF , 100oC
N R
N
O
O
N
Pd
Ph
OAcO
O
Ph2Si(OH)Me
N
Pd
Ph
O
O
C-H ActivationPd(0)Ln
Pd(II)Ln
N
O
O
J. AM. CHEM. SOC. 2002, 124, 13372-13373
C-O and C-X Bond Formation
N
5 mol% Pd(OAc)2
75-100oC NX
PhI(OAc)2 , MeCN X=OAc , 86%PhI(OAc)2 , MeOH X=OMe , 95%NBS , MeCN X=Br , 93%NCS , MeCN X=Cl , 95%
N
[PdII] DirectedC-H Activation
NPdII
L
L
PhI(OAc)2
Oxidation
NPdIV
L
L
OAc
L
-[PdII] ReductiveElimination
NAcO
J. AM. CHEM. SOC. 2004, 126, 2300-2301
J. AM. CHEM. SOC. 2006, 128, 7134-7135
RNHTf
Pd(OTf)2-2H2ONMP , DCE ,120oC
N FOTf
RNHTf
F
J. AM. CHEM. SOC. 2009, 131, 7520–7521
C-N Bond Formation
O
O
TsHN
Z:E=10:1
10 mol% Pd(OAc)22 eq. PhI(OAc)2
1 eq. Bu4NOAcMeCN , 25oC , 7h OAc
OTsN
O
92% yield , 9.5:1 dr
O
O
TsHN
10 mol% Pd(OAc)22 eq. PhI(OAc)2
1 eq. Bu4NOAcMeCN , 60oC , 2.5h OAc
OTsN
O
65% yield ,>20:1 dr
PdIIX2
PdIIX
OTsHN
O X
O
O
TsHN
PdIIX
OTsN
OB:
BHX
PdIV(OAc)X2
OTsN
O
OAc
OTsN
O
PhI(OAc)2
PhI
Proposed Catalytic Cycle
J. AM. CHEM. SOC. 2005, 127, 7690-7691
Domino Catalysis Involving Pd(IV) Catalysts
O O
Ph 5 mol% Pd(OAc)26 mol% bipy
1.1eq PhI(OAc)2O
HO
Ph
O
X
Ph[PdII]
AcOHX
OAcR
[PdII]
X
OAcR
Oxidant
Nu
X
OAcR
PdIV
Nu
Oxidant
Nu
X
OAcR
PdIVNu
80oC , 5h AcOHO O O O
OAc
Ph
AcO
Ph
OAc
(79%) <5% Observed <5% Observed
J. AM. CHEM. SOC. 2007, 129, 5836-5837
O
HOAc
Ph
O
Me
[PdII]O O
Ph
O O
PdIIPh
OAc
O
OAcPhPdII
MeH
OO
OAcPh
O
HMe
PdII
O
OAcPh
O
HMe
PdIVOAc
hydrolysis
O
HO
Ph
O
Me
PhI(OAc)2
PhI
O
OAcPh
O
[PdII-H]PhI(OAc)2
ReinsertionOxidative
Functionalization O O
OAc
PhAcO
Proposed Mechanism
First example of enantioselective palladium(IV) catalysis
R1
O O
R2Pd-(i-Pr-SPRIX)
PhI(OAc)2or PhI(OCOCF3)2
O
R2
O
R1
O
up to 95% ee
O N N O
H
i-Pr
i-Pr i-Pr
i-Pr
H
i-Pr-SPRIX
J. AM. CHEM. SOC. 2009, 131, 3452–3453
Problems
1.Little is known about the ligand effect of Pd(IV) complexes
2.Enantioselective synthesis using chiral ligands through Pd(IV) intermediates has not been forthcoming
3.Applications to natural product synthesis are lacking
4.Detailed mechanistic investigation
The development of palladium(IV) catalysis has just begun, it has already enabled the development of a number of significant new transformations. These reactions are marked by their high selectivity and synthetic robustness, and almost all are based on the use of catalysts that are generated in situ from commercially available palladium salts.
Conclusion
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