A highly enantioselective Mannich reaction of aldehydes with cyclic N-acyliminium ions by synergistic catalysis.

Matched combinations of Brønsted or Lewis acids with suitable pro-electrophiles and secondary amine organocatalysts enable the novel enantioselective syntheses of carbamoyl dihydroquinoline and tetrahydropyridine derivatives with concomitant formation of two stereocenters. A short formal asymmetric synthesis of (2R,2'R)-threo-methylphenidate (Ritalin) is also described.