In the present paper, the ab initio molecular orbital computations of the enantioselective reduction of acetophenone catalyzed by chiral sulfur-containing oxazaborolidine catalysts are carried out by use of the HF method with 6-31G^* basis sets. In the reduction, catalyst- borane adducts, catalyst-borane-ketone adducts, and catalyst- alkoxyborane adducts are generated, and the further decomposition of catalyst-alkoxyborane adducts are generated, and the further decomposition of catalyst-alkoxyborane adducts takes place. The formation of catalyst-borane adducts, catalyst-borane-ketone adducts, and catalyst-alkoxyborane adducts are exothermic, endothermic, and exothermic respectively, whereas the decomposition of catalyst- alkoxyborane adducts into catalyst and alkoxyborane is endothermic. Both catalyst-borane-ketone adducts and catalyst-alkoxyborane adducts have four stable structures. Among the four structures of the catalyst-borane-ketone adducts, the one with the greatest tendency for the hydrogen transfer to take place is the one with the second lowest energy, with a twisted boat structure. Each of catalyst- alkoxyborane adducts contains a B-O-B-N4-membered ring. In spite of the great tensile stress of the 4-membered ring, the catalyst- alkoxyborane adducts are quite stable.

Key words: SULFUR HETEROCYCLICS COMPOUNDS, CATALYST, ACETOPHENONE, REDUCTION REACTION, QUANTUM CHEMISTRY, AB INITIO CALCULATION, CHIRALITY