Copper-Catalyzed Three-Component Formal [3+1+2] Benzannulation for Carbazoles and Indoles Synthesis

Three-component formal [3+1+2] benzannulation reactions of indole-3-carbaldehydes or 1-methyl-pyrrole-2-carbaldehydes with two different molecules of saturated ketones have been successfully developed under Cu-catalyzed and TEMPO-mediated conditions. Various unsymmetrically substituted carbazoles and indoles were obtained up to 95% yield. Furthermore, the resulting products exhibit unusual AIE properties in the solid state. This method features high atom-economy, cheap catalyst and oxidants, wide substrate scope and saturated ketones as one-carbon and two-carbon source, thus providing an efficient approach to polycyclic carbazole and indole compounds.