Synthesis of 2,3-Disubstituted Pyrroles and Pyridines from 3-Halo-1-azaallylic Anions

A new synthesis of 2,3-disubstituted pyrroles and pyridines is described. The reaction of 3-halo-1-azaallylic carbanions, regiospecifically generated from α-halogenated ketimines, with ω-iodoazides led to the regiospecific formation of ω-azido-α-haloketimines. Treatment of these functionalized imines with tin(II) chloride afforded halogenated five- and six-membered cyclic imines, which were transformed under mild conditions into 2,3-disubstituted pyrroles and pyridines. The stereoselective reduction of 2,3-dialkyl-3-chloro-1-pyrrolines to afford cis-2,3-dialkyl-3-chloropyrrolidines is also reported.