Improved Methodology for the Preparation of Chiral Amines

with 97% yield for phenyl methyl N-aryl imine (structure 1, figure 2.3). They also tested their
catalyst for different substituted phenyl methyl N-aryl imines. p-OMe (93% ee, 95% yield),
p-Br (95% ee, 98% yield), m-Br (94% ee, 82% yield), p-CF 3 (96% ee, 85% yield), para-NO 2
(95% ee, 96% yield) phenyl methyl N-aryl imines were reduced successfully (structure 3,
figure 2.3). 2-naphthyl methyl N-aryl was reduced with (93% ee, 92% yield) and p-methoxy
substituted naphthyl methyl N-aryl imine (91% ee, 97% yield).
They also reported the use of formamide derivative of piperazine carboxylic acid. [41] Using 10
mol % of the catalyst (catalyst 22, figure 2.4), 2.0 equiv Cl 3 SiH, CH 2 Cl 2 , -20 °C, 48 h,
resulted in 89% ee with 95% yield for phenyl methyl N-aryl imine (structure 1, figure 2.3)
and for phenyl ethyl N-aryl imine the ee was 94% with 92% yield (structure 2, figure 2.3). p-
NO 2 (90% ee, 99% yield), p-Br (89% ee, 81% yield) and p-Me (85% ee, 71% yield) phenyl
methyl N-aryl were successfully reduced. 2-naphthyl (88% ee, 63% yield) and 6-OMe 2-
naphthyl methyl N-aryl imine (85% ee, 64% yield) were reduced. p-F (95% ee, 87% yield),
p-Cl (94% ee, 83% yield), p-Br (95% ee, 89% yield), p-Me (88% ee, 87% yield) and p-OMe
(90% ee, 83% yield) phenyl ethyl N-aryl imine were reduced with high yields and ees.
Phenyl n-propyl N-aryl imine was reduced with 90% ee and 88% yield and phenyl n-butyl N-
aryl imine was reduced with 89% ee and 84% yield.
They were also successful in using chiral sulfinamides based on Ellman auxiliary [(R)-tertbutansulfinamide.
[42] Using of 20 mol % of the catalyst (catalyst 23, figure 2.4), 2.0 equiv
Cl 3 SiH, CH 2 Cl 2 , -20 °C, 24 h, the ee was 92% with 92% yield for phenyl methyl N-aryl
imine (structure 1, figure 2.3). p-OMe (93% ee, 98% yield), p-Br (92% ee, 92% yield), p-NO 2
(90% ee, 94% yield) and p-CF 3 (92% ee, 93% yield) phenyl methyl N-aryl imines were
reduced (structure 3, figure 2.3).
In 2007 they reported the use of proline derived tetramide catalyst for imine reduction. [43]
Using 10 mol % of the catalyst (catalyst 24, figure 2.4), 2.0 equiv Cl 3 SiH, CH 2 Cl 2 , 0 °C, 16
h, the ee was 77% with 93% yield for phenyl methyl N-aryl imines. For substituted phenyl
methyl imines the ees were lower compared with his other catalytic systems (structure 1,
figure 2.3)
48