Enantioselective borane reduction of ketones catalysed by a chiral oxazaphospholidine–borane complex

Abstract
The chiral oxazaphospholidine–borane complex 2 was used as catalyst (2 mol %) in asymmetric reduction of ketones by borane with an enantioselectivity ranging from 33 to 92% at 110 °C and 100% conversion; under stoichiometric conditions the reduction proceeded with 99% enantiomeric excess.