Chemistry Reference
In-Depth Information
O
O
Catalyst
Conditions
Ph
2
CN
Ph
2
CN
+
*
PhCH
2
Br
O
t-
Bu
O
t-
Bu
2a
H
Ph
3a
-
X
-
+
Cl
H
N
OH
+
N
OR
N
N
H
Ar
1b
(Ar = Ph)
1c
(Ar = 9-anthracenyl)
4a
(R = H, X = Cl)
4b
(R = allyl, X = Br)
1b
(10 mol %)
1c
(10 mol %)
4a
(10 mol %)
4b
(10 mol %)
50% NaOH
aq
50% KOH
aq
50% KOH
aq
CsOH•H
2
O
CH
2
Cl
2
Toluene
Toluene
CH
2
Cl
2
25°C, 9h
rt, 18 h
rt, 18 h
-78°C, 23 h
75%, 66% ee
(
R
)
63%, 89% ee
(
R
)
68%, 91% ee
(
S
)
84%, 94% ee
(
S
)
Scheme 2C.2.
O
O
(
S
,
S
)-
5
(1 mol %)
Ph
2
CN
Ph
2
CN
+
RBr
O
t-
Bu
O
t-
Bu
50% KOH
aq
Toluene, 0°C
2a
H
R
3
Ar
(R : PhCH
2
)
5a
: 73%, 79% ee
5b
: 81%, 89% ee
5c
: 95%, 96% ee
5d
: 91%, 98% ee
5e
: 90%, 99% ee
B
r
-
+
N
(R : 1-NpCH
2
)
5e
: 90%, 99% ee
(R : CH
2
=CHCH
2
)
5e
: 80%, 99% ee
Ar
(
S
,
S
)-
5
Ph
F
F
Ar = H (
5a
), Ph (
5b
)
Ph
F
5c
5d
5e
Scheme 2C.3.
salts. The performances of the representative catalysts in the benzylation of
2a
are sum-
marized in Schemes 2C.4 and 2C.5 .
To fully induce the potential catalytic activity of
N
-spiro chiral ammonium salt such
as
5d
, we have developed binary phase-transfer catalysis using an appropriate achiral
cocatalyst. For instance, the phase-transfer-catalyzed alkylation of
2a
with benzyl
bromide under the infl uence of
5d
(0.05 mol %) turned out to be sluggish to give
3a
in
