Biomedical Engineering Reference
In-Depth Information
TABLE 7.3 Phase-Transfer-CatalyzedEnantioselectiveMichael AdditionofGlycineSchiff Base
O
O
X
catalyst
conditions
Ph
2
C
N
Ph
2
C
N
+
O
t-
Bu
O
t-
Bu
O
H
COX
2a
Yield
(%)
ee (%)
(Configuration) Reference
Catalyst (mol%)
Conditions
X = OMe,
CsOH
85
95
[44]
Br
-
H
2
O,
CH
2
Cl
2
, -78
C
+
H
N
O
N
4b
(10 mol%)
NEt
3
X = Me, Cs
2
CO
3
,
PhCl, -30
C
100
75
[45]
+
O
Ar
2
Br
-
O
Ar
+
NEt
3
(
S
)-
39
(1 mol%)
(Ar = 4-CF
3
-C
6
H
4
)
-
X = OBn, Cs
2
CO
3
,
PhCl, -30
C
84
81
[12]
2BF
4
Me
4-Me-C
6
H
4
N
+
O
Pr
Pr
4-Me-C
6
H
4
4-Me-C
6
H
4
O
N
+
Me
4-Me-C
6
H
4
8c
(5 mol%)
Br
-
X=O
t
-Bu,
CsOH·H
2
O,
t
-
BuOMe, -60
C
73
77
[46]
RO
OR
+
N
RO
OR
40
(10 mol%)
(R = 4-CF
3
-C
6
H
4
CH
2
)
Ar
X = OMe, CsCl (10
mol%), K
2
CO
3
,
CPME, 0
C
88
92
[47]
Br
-
+
N
O
Ar
(S)-
41a
(1 mol%)
(Ar = 3,5-(3,4,5-F
3
-C
6
H
2
)
2
-C
6
H
3
)
Enantioselective conjugate additions of 3-substituted oxindoles to Michael
acceptors are one of the key topics in catalytic asymmetric synthesis; this is because
oxindoles are important building blocks in numerous natural alkaloids and in many
pharmaceuticals [51]. We developed catalytic asymmetric Michael additions of 3-
substituted oxindoles to methyl vinyl ketone catalyzed by a quaternary tetraalkyl-
phosphonium bromide
45
(Scheme 7.20) [52]. In the course of this study, we were
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