Asymmetric reduction of prochiral ketones with borane using chiral squaric amino alcohols derived from camphor as catalysts

A series of new chiral squaric amino alcohols derived from (R)-(+)-camphor and squaric acid were synthesized, and applied to the enantioselective reduction of prochiral ketones with borane to give secondary alcohols with excellent enantiomeric excesses (up to 99%).