Expeditious synthesis of CF₃-phenanthridones through a base-mediated cross-conjugated vinylogous benzannulation (VBA)

Herein, we report a mild, efficient, and rapid approach for the preparation of CF₃-phenanthridones through a cross-conjugated vinylogous [4 + 2] benzannulation of easily accessible 4-methyl-3-trifluoroacetylquinolones and nitro-olefins. The present transformation is superior to previous approaches for obtaining CF₃-phenanthridones, in that it proceeds exclusively with the assistance of a simple base, eliminating the need for transition metal catalysts or oxidants. The strong electron-withdrawing nature of the CF₃-group present in the quinolone moiety promotes the formation of a reactive cross-conjugated vinylogous enolate.