Cooperative Catalysis of Chiral Tetraaminophosphonium Carboxylates

Significance

The authors report a highly enantio­selective direct Mannich-type reaction of ­azlactones and various aliphatic sulfonylimines, catalyzed by a [5,5]-P-spirocyclic tetraaminophosphonium carboxylate. It was found that the basicity of the carboxylate anion had a strong influence on the reaction rate. Thus, a pivalate anion accelerated the reaction compared to formate or acetate. The Mannich products were obtained in excellent yields (91-99%) and enantioselectivities (er = 95:5 to 98:2).