Chiral Brønsted Acid-Catalyzed Direct Asymmetric Mannich Reaction

A chiral Brønsted acid-catalyzed direct asymmetric Mannich reaction has been described. Various phosphoric acids, prepared from BINOL and H₈-BINOL derivatives, have been evaluated for catalyzing the direct Mannich reaction. In the presence of a truly catalytic amount of the phosphoric acid, anti-selective Mannich reactions of cyclic ketones with a wide scope of aldimines were obtained in high yields with excellent enantioselectivities (up to 98% ee) and high diastereomeric ratios (up to 98/2 dr). A one-pot Mannich reaction using aromatic ketones as donors proceeded smoothly to give β-amino carbonyls with fairly good enantioselectivities.