Piperidine enamines derived from acetone, acetophenone, cyclopentanone and cyclohexanone react easily in minutes with methyl 3,3,3-trifluoropyruvate (1) to afford products of the aldol condensation in high yields at room temperature, which is in contrast to the direct aldolization of 1 with the ketones.
piperidines - nucleophilic additions - ketones - ene reactions - aldol reactions