preparation of allyl sulfoxides by palladium-catalyzed allylic alkylation of sulfenate anions
DESCRIPTION
Preparation of Allyl Sulfoxides by Palladium-Catalyzed Allylic Alkylation of Sulfenate Anions. Guillaume Maitro, Guillaume Prestat, David Madec, * and Giovanni Poli *. J. Org. Chem. 2006 , 71 , 7449-7454. 演講者:化生四 張永宏. Allyl Sulfoxides. - PowerPoint PPT PresentationTRANSCRIPT
Preparation of Allyl Sulfoxides by Palladium-Catalyzed Allylic Alkylation of Sulf
enate Anions
Guillaume Maitro, Guillaume Prestat,
David Madec, * and Giovanni Poli *
J. Org. Chem. 2006, 71, 7449-7454
演講者:化生四 張永宏
2
Allyl Sulfoxides
• Allyl sulfoxides are versatile and valuable building blocks in organic synthesis .
S
R
Ph O S
Ph
O
R [T]
1. BuLi2. PhSCl
R OH
Acc. Chem. Res. 1974, 7, 147.• It is proved by their use in the preparation of various functionalized compounds and natural products.
SO
PhR Bu2SnH, AIBN OR
Angew. Chem. Int. Ed. 2002, 41, 4323.
azobisisobutyronitrile
NN
N
N
S
R
Ph O S
Ph
O
R
PPh
Ph
Ph
O
R
H2O
OH
R
SOPh
[2,3]-sigma. O SPh
O
O O Bu3SnH
- Bu3Sn
O
RR R
R
R R
Bu3Sn
3
Palladium-Catalyzed Allylic Alkylation of Sulfur Nucleophiles
4
Generations of Carbon-Heteroatom Bonds by Palladium Complex
OAc+ TsNa + 4H2O
Pd(PPh3)4
(5 mol %)
rt, THF-MeOHTs
Ts
(Ts = p-CH3C6H4SO2)
+
Chem. Lett. 1981, 1357-1360.
R-Z O
OPdLn
CO2
PdL
L+ Z
NuH
PdLn
PdLn
RZH + Nu
R-Z
a
b
Synlett 1993, 680-682.
(Nu = sulfur nucleophiles)
R-Z O
O
+ [Pd]Z-R
O
O
[Pd][Pd]
CO2
SR
SR
[Pd]
OAc[Pd]
AcO
[Pd]
+
[Pd]
[Pd]
Ts
TsTs
+
[Pd]
5
Synthesis of Allyl Sulfoxides
6
Mechanism of The Synthesis of Sulfenate
7
Methods of Generation of Sulfenate Anions
• Sulfur oxidation
• Addition-elimination reaction
• Ring-opening reaction
• Ring manipulation route
• Sigmatropic rearrangement
• Metal insertion reaction
• Retro-Michael reaction
8
Generation of Sulfenate Anions by Sulfur Oxidation
• Sulfenate anions are of limited stability.• A competitive oxidative pathway leading to symmetri
cal disulfides may occur.• The oxidizing agents employed up to now, m-CPBA a
nd hydrogen peroxide, were not particularly well suited to this task.
SH
R1
R2
R3
1) MeLi, -78oC, THF
2) 1, -78oC3) R4X, -78oC to rt X = Br, I
S(O)R4
R1
R2
R3
NO
Me
t-Bu SO2Ph
1
J. Org. Chem. 1997, 62, 8626-8627
S
R1
R2
R3
NO
Me
t-Bu SO2PhS
R3
R2
R1
OMe
N
t-Bu
SO2Ph SO
R1
R2
R3
9
Generation of Sulfenate Anions by Metal Insertion Reaction
n-Bu S(O)Tol
1) PdCl2(dppf) (2 mol%) Et2Zn (2 eq) THF (0.1 M) -78oC to rt
2) H+
n-Bu
TolS(O)
S(O)Tol+
n-Bu
Et
S(O)Tol
Org. Lett. 2001, 3, 3627-3629
dppf = diphenylphosphinoferrocene Fe
Ph2P
PPh2
10
Generation of Sulfenate Anions by Ring-Opening Reaction
S
OLDA
THF, -78oC
S
OLi
RX S RO
Synlett, 1996, 1996, 247
S
O LDA
H S
O
S
O
11
Methods of Generation of Sulfenate Anions
• Sulfur oxidation
• Addition-elimination reaction
• Ring-opening reaction
• Ring manipulation route
• Sigmatropic rearrangement
• Metal insertion reaction
• Retro-Michael reaction
12
Generation of Sulfenate Anions by retro-Michael reaction
SR1 CO2R2
O1. Base 2. R3X S
R1 R3
O
*
R1 = aryl, alkylR2 = Me, Et
ee up to 29%with n-BuLi/(-)-sparteine as base
J. Org. Chem. 2005, 70, 2812-2815
R1SO
13
The Catalytic Cycle for Transition Metal-Catalyzed Allylic Alkylations
14
Preparation of β-Sulfinylesters
a:
b:
c:H3C
CH3
CH3
15
Mechanism of The Preparation of The β-Sulfinylesters
O
OH
HO
SO
O
K
OHO
O
OH
HO
SO
K
OH
OS
R
CO2t-BuSR
CO2t-Bu
O
R S
CO2t-BuBase
H SR SRCO2t-Bu
SRCO2t-Bu
H2O
16
Mechanism of The Formation of Sulfenate Anions
retro-Michael reaction
RS O
Ot-Bu
O
RS O
Ot-Bu
O
Base
HSO
R + O
Ot-Bu
17
Optimization of Reaction Conditions
( dppe = cis-Ph2PCH=CHPPh2 )
18
Allylic Acetates
OAc Ph OAc
Ph
OAc
OAcOAc
1-phenylallyl acetate
allyl acetate cinnamyl acetate
cyclopent-2-enyl acetate cyclohex-2-enyl acetate
19
Palladium-Catalyzed Allylic Alkylation of Sulfenate Anions
20
The Interconversion Equilibrium between The Two Diastereomers
Sp-Tol
O
OS p-Tol
Sp-Tol O
Synlett, 2004, 995-998
(R,R/S,S) (S,R/R,S)
21
Palladium-Catalyzed Allylic Alkylation of Sulfenate Anions
22
Palladium-Catalyzed Allylic Alkylation of Sulfenate Anions
23
Allylic Alkylations in Biphasic Conditions
24
Conclusions
We have reported the first palladium-catalyzed allylation of sulfenate anions.
This new, smooth, and operationally very simple method further extends the set of sulfur-based nucleophiles that can be successfully allylated under palladium catalysis.
The stereogenic nature of the sulfur atom in the generated allyl sulfoxides, and the potential sulfoxide-sulfenate rearrangement associated to these compounds are expected to make of this reaction a synthetically interesting transformation.
25
S
O LDA
H S
O
S
O
n-BuLi/(-)-sparteine