Chemistry Reference
In-Depth Information
O
Ph
COOR
O
Catalyst
Conditions
COOR
+
Ph
Ph
Ph
COOR
COOR
Ar
Ar
Ar
-
Br
-
Br
OH
4e
(10 mol %)
R = Bn
K
2
CO
3
Toluene
rt
91%, 70% ee
32
(3 mol %)
R = Et
K
2
CO
3
Toluene
-20°C
99%, 90% ee
Maruoka and others [40]
+
H
N
+
t
-Bu
N
O
N
OMe
OH
t
-Bu
Kim and others [39]
Ar
Ar
Ar
4e
32
(Ar = 3,5-Ph
2
-C
6
H
3
)
Scheme 2C.16.
(
R
,
R
)-
5g
(2 mol %)
O
H
O
O
O
1 N HC
l
+
Ph
2
C
N
R
O
t
-Bu
O
t
-Bu
R
H
THF
1% NaOH
aq
(15 mol %)
NH
4
Cl (10 mol %)
Toluene, 0°C
NH
2
2a
anti
-
33
(anti/syn = 96:4)
F
3
C
CF
3
R =
Ph(CH
2
)
2
Me(CH
2
)
4
i
-Pr
3
SiOCH
2
Me
c
-Hex
: 82%, 98% ee
: 79%, 97% ee
: 73%, 98% ee
: 54%, 99% ee
: 83%, 98% ee
Ar
-
Br
+
N
Ar =
CF
3
(CPME as solvent)
Ar
(
R
,
R
)-
5g
CF
3
Scheme 2C.17.
chemical process for the synthesis of optically active
anti
-
β
- hydroxy -
α
- amino esters
33
(Scheme 2C.17 ) [41] .
Phase-transfer-catalyzed direct Mannich reaction of glycine Schiff base
2a
with
-
imino ester
34
was achieved with high enantioselectivity by the utilization of
N
- spiro
chiral quaternary ammonium bromide
5e
as catalyst (Scheme 2C.18) [42]. The more
general and highly diastereoselective Mannich-type reaction was developed by Ohshima
and Shibasaki. The original tartrate-derived diammonium salt
8
was modifi ed by intro-
ducing an aromatic ring at the acetal side chains, and 4-fl uorophenyl - substituted
8d
was
identifi ed as an optimal catalyst for the reaction of
2a
with various
N
- Boc imines
35
under solid (Cs
2
CO
3
) - liquid (fl uorobenzene) phase-transfer conditions as exemplifi ed in
Scheme 2C.18 [43] .
α
