Base-Mediated Cyclization of N-Benzyl Ketimines with Diynes: Conditions-Controlled Switching between N-Vinyl Pyrroles and 2H-Azepines.

Semistabilized azaallyl anions, generated from N-benzyl ketimines in the NaOtBu/DMSO superbase medium, undergo conditions-controlled formal [3 + 2] or [4 + 3] cyclization with diaryldiynes. Consequently, selective switchable syntheses of triarylsubstituted α-arylated N-vinyl pyrroles (in up to 64% yield) and tetraarylated 2H-azepines (in up to 75% yield) have been developed. The synthetic value of this strategy has been validated by successful gram-scale syntheses of both products.