Unconventional bifunctional Lewis-Brønsted acid activation mode in bicyclic guanidine-catalyzed conjugate addition reactions

Abstract

DFT calculations have demonstrated that the unconventional bifunctional Brønsted-Lewis acid activation mode is generally applicable to a range of nucleophilic conjugate additions catalyzed by bicyclic guanidine catalysts. It competes readily with the conventional bifunctional Brønsted acid mode of activation. The optimal pro-nucleophiles for this unconventional bifunctional activation are acidic substrates with low pK a, while the best electrophiles are flexible 1,4-diamide and 1,4-diester conjugated systems.