Al(OtBu)3 as an Effective Catalyst for the Enhancement of Meerwein–Ponndorf–Verley (MPV) Reductions

The Meerwein–Ponndorf–Verley (MPV) reduction of aldehydes and ketones has been the cornerstone in many multistep syntheses. Herein we report the use of Al(OtBu)3 instead of the commonly used Al(OiPr)3 which results in a dramatic rate increase and significantly lower catalyst loading for the reduction of (1) model compounds benzaldehyde and acetophenone, and (2) N-(tert-butyloxycarbonyl)-(3S)-3-amino-1-chloro-4-phenyl-2-butanone or (S)-CMK, a key intermediate in HIV protease inhibitor synthesis.