New Chiral Borohydride Based Reducing Agent: Asymmetric Reduction of 9-Anthryl Trifluoromethyl Ketone and Other Carbonyl Compounds

Abstract

(S)-(+)-2-(α-Hydroxybenzyl)benzimidazole (1) and (S)-(-)-2-benzimidazole-1-ethanol (2) were synthesised and converted to chiral borohydrides which reduced prochiral ketones to the corresponding chiral alcohols in high yields (80 to 100%, e.e. 42 to 95%). This is the first report of sodium borohydride modified by 1,2-amino alcohol.

Notes

Ref 4 of ref. 15 c.

R-(−)-[α]_D ²⁵ −4.8° (c 15.3, C₆H₆ ref. 10c)

Rotation found [α]_D ²⁷ −30.5° (c 1.5, CHCl₃); Lit R-(−)-[α]_D ²⁵ −29° (c 6.0, CHCl₃).^14a