Design, synthesis and structure of new chiral squaric acid monoaminoalcohols and diaminoalcohols and their use as catalysts in asymmetric reduction of ketones and diketones

Many chiral squaric acid aminoalcohols and C2-symmetric diaminoalcohols have been synthesized and their in situ formed chiral boron heterocycles have been used as catalysts for the enantioselective reduction of prochiral ketones and diketones by borane to give alcohols with up to 99% enantiomeric excess and 99% yield. The effects of solvent, catalyst–substrate ratio and temperature were also investigated.