Improved Methodology for the Preparation of Chiral Amines

9 9 84% 94%
10 10 85% 93%
2.3.Asymmetric Reduction of N-aryl Imines
2.3.1. Synthesis of N-Aryl Imines.
N-aryl imines are synthesized from their corresponding ketones and N-aryl amines. They are
mixed in anhydrous toluene in the presence of NaHCO 3 and 4Å ctivated molecular sieves.
The mixture is heated for 12 h at 80 °C. The product is purified by crystallization and
distillation (scheme 2.2). [17]
NH 2
R 3
O
+
R 1 R 2
NaHCO 3 ,4ÅMS
toluene, 80 °C,12h
( mediocre-good yield)
N
R 1 R 2
R 3
reduction
high yield
R 3
HN
cerium ammonium nitrate NH 2
MeOH/H 2 O, 0 °C, 6h
R 1
* R 2
R 1
* R 2
(good-high yield)
Scheme 2.2 General Strategy for Synthesis of N-Aryl Imines.
Figure 2.3: General Imine Structures:
N
R
N
R
N
R
R 1
1
2
3
40