Chemistry Reference
In-Depth Information
O
R
1
= Alkyl, CH
2
OH, CH
2
OAc,
CH
2
OPMB, (CH
2
)
3
OTBS
R
2
= Me, CH
2
Ph, Ph, Ar
CCl
3
R
2
O
COP-OAc
86c
CH
2
Cl
2
HN
R
2
CO
2
H
+
R
1
O
R
1
(
Z
)-
87
91
(Up to >99% ee)
N
*
N
OAc
O
AcO
Pd
C
*
HN
Pd
C
2
O
NH
Cl
3
C
Pd
Cl
3
C
R
1
O
R
1
O
N
R
2
CO
2
H
91
O
Ph
C
o
Ph
N
(
Z
)-
87
OCOR
2
R
1
*
Pd
C
Ph
Ph
HN
OCOR
2
C
Pd
N
Cl
3
C
COP-OAc
86c
*
OAc
R
1
O
Scheme 5.28.
O
NHSO
2
Ar
FOP-TFA
83
CH
2
Cl
2
-MeNO
2
O
NSO
2
Ar
O
O
OAc
(
Z
)-
92
93
(Up to 93% ee)
(
Z
)-
92
93
FOP-TFA
83
C
N
NC
*
ArO
2
S
ArO
2
S
O
*
*
ArO
2
S
N
Pd
O
Me
N
Pd
C
Pd
O
N
N
or
O
Me
O
O
O
O
O
OAc
O
9
4
9
5
96
Scheme 5.29.
catalyst to the double bond and serving as a leaving group. The reaction of (
Z
) -
87
with
phenols provided branched allylic aryl ethers in high enantiopurity and yield under
similar reaction conditions [37b]. In these catalytic substitution reactions, high branched/
linear ratio was observed to give the branched allylic products.
The use of FOP-TFA
83
promoted the cyclizations of allylic
N
- arylsulfonylcarba-
mates (
Z
) -
92
, providing the effi cient method for asymmetric synthesis of fi ve - membered
nitrogen heterocycles
93
(Scheme 5.29) [37c]. Enantioselectivity was enhanced in more
polar solvents, a 1:1 mixture of CH
2
Cl
2
- MeNO
2
being optimal in terms of both yield and
enantioselection. Two mechanisms involving aminopalladation of the alkene via
94
and
insertion of the alkene into the Pd-N bond of
95
can be considered. Enantioenriched
2-pyrrolidinones and 2-imidazolidinones can be prepared in similar fashion.
