Catalytic imino-Diels–Alder reactions of 2-aminodienes: a simple entry into structurally diverse pipecolic acid derivatives

The stereoselective synthesis of 4-aminotetrahydropyridines by cycloaddition reaction of 2-amino-1,3-butadienes with N-alkyl and N-aryliminoesters in the presence of a catalytic amount of a Lewis acid is described. The reaction proceeds with differently substituted 2-aminodienes, giving rise to structurally diverse pipecolic acid derivatives.