Cyclic Aldimines as Superior Electrophiles for Cu-Catalyzed Decarboxylative Mannich Reaction of β-Ketoacids with a Broad Scope and High Enantioselectivity

A novel Cu-catalyzed enantioselective decarboxylative Mannich reaction of cyclic aldimines with β-ketoacids is described. The cyclic structure of these aldimines, in which the C═N bond is constrained in the Z geometry, appears to be important, allowing Mannich condensation to proceed in high yields with excellent enantioselectivities. A chiral chroman-4-amine was synthesized from the decarboxylative Mannich product in several steps without loss of enantioselectivity.