Direct Mannich-Type Reactions Promoted by Frustrated Lewis Acid/Brønsted Base Catalysts

Abstract

Direct Mannich-type reactions that afford both α- and β-amino esters by the reaction of a broad range of carbonyl compounds and aldimines are disclosed. The transformation is promoted by a sterically frustrated Lewis acid/Brønsted base pair, which is proposed to operate cooperatively: Within the catalyst complex, an enolate is generated that then reacts with a hydrogen-bond-activated imine. Noncovalent interactions between reactants and the catalyst provide selectivity and new opportunities for future catalyst design.

Keywords: Lewis acids; Mannich-type reactions; acid-base catalysis; boron; frustrated Lewis pairs.