Computational Evaluation of Enantioselective Diels−Alder Reactions Mediated by Corey’s Cationic Oxazaborolidine Catalysts

The cationic oxazaborolidine-catalyzed Diels-Alder reactions of butadiene and a series of five dienophiles have been studied using density functional theory (B3LYP/6-31G(d)). In each case, the computational results successfully reproduce the experimentally observed sense of stereoinduction and enantiomeric ratio. The computed structures of the lowest energy Lewis acid-carbonyl complexes and Lewis acid-transition state complexes are closely related to the models for stereoselection proposed by Corey and co-workers.