QUANTUM-CHEMICAL MODELING OF CHIRAL CATALYSIS .15. ON THE ROLE OF HYDRIDE-BRIDGED BORANE-ALKOXYBORANE COMPLEXES IN THE CATALYTIC ENANTIOSELECTIVE REDUCTION OF KETONES PROMOTED BY CHIRAL OXAZABOROLIDINES

Hydride-bridged borane - alkoxyborane complexes of oxazaborolidines we re investigated by means of ab initio molecular orbital methods (RHF). The complexes wire found to be stable in the absence of Lewis basic s olvents. In the presence of a Lewis basic solvent the borane - alkoxyb orane complexes were predicted to decompose leading to the formation o f borane - solvent complexes of the oxazaborolidines. A new class of o xazaborolidine catalysts, of which the mechanism of regeneration would be based on borane - borane hydride exchange, was invented.