Divergent Pd-catalyzed and radical cyclizations of nucleophilic cyclic enamines derived from functionalized amine and aldehyde fragments.

Tetrahydropyridines carrying pendant halide functionality at the enamine beta-carbon have been prepared by condensation between appropriately functionalized aldehydes and a vinylogous Mannich adduct. Those enamines display divergent behavior in radical and Heck reactions. Thus, radical addition takes place in a 5-exo-trig fashion whereas Heck couplings follow a 6-endo-trig pathway. The resulting polycyclic products are obtained with high regio- and stereoselectivity.