Enantioselective reductions of aromatic ketones with ammonia–borane complexes of chiral tetraphenyl-18-crown-6 derivatives
Abstract
Enantioselective reductions of prochiral aromatic ketones with adducts formed between ammonia-borane and (2R,3R,11R,12R)- and (2S,3S,11S,12S)-tetraphenyl-1,4,7,10,13,16-hexaoxacyclo-octadecane, (RRRR)-(3) and (SSSS)-(3), have afforded the corresponding (S) and (R) aromatic secondary alcohols with enantiomeric excesses of 20–67%.