[4 + 2] Cycloaddition of trifluoromethyl ketimines with 2-alkenyl azaarenes through selective C–F bond cleavage of CF3

Abstract

We have developed a new [4 + 2] cycloaddition of trifluoromethyl ketimines with 2-alkenyl azaarenes through selective C–F bond cleavage of CF₃. The reactions are promoted by 2,2,6,6-tetramethylpiperidine (TMP) under mild conditions to give cis-tetrahydropyridine products in moderate yields. Density functional theory (DFT) calculations reveal that the in situ formed (E)-N-(2,2-difluoro-1-phenylvinyl)-1-phenylmethanimine is the key intermediate for the formation of cis-tetrahydropyridine products which have the lowest energy among the four possible products.