Enantiomerically pure 2-piperazinemethanols as novel chiral ligands of oxazaborolidine catalysts in enantioselective borane reductions

Novel enantiomerically pure 2-piperazinemethanols (3-5) were synthesized fr om 2-piperazinecarboxylic acid 1. The asymmetric reduction of aromatic keto nes, ketimine and oxime ether has been performed with reagents prepared fro m 2-piprazinemethanol and borane to yield enantiomerically enriched alcohol s and amines, respectively. The preferred absolute configuration of the pro duct was dependent on the structure of the sulfonyl substituent in the chir al ligand. (C) 1999 Elsevier Science Ltd. All rights reserved.