Copper-Catalyzed Radical Cascade Cyclization of N-Substituted Indole-3-Aldehydes with Aryl Alkenes: Access to Pyrrolo[1,2-a]indole Scaffolds.

Herein, we report a Cu-DTBP-catalyzed [3 + 2] cycloaddition reaction between 1-(2-oxo-2-phenylethyl)-1H-indole-3-aldehyde and arylalkene, using DMF as the solvent. Under relatively mild reaction conditions, a series of indole compounds were synthesized in moderate yields (up to 73%). This protocol features good functional group tolerance and high atom economy. In addition, we synthesized a total of 20 target compounds, providing a reliable and straightforward method to obtain structurally diverse pyrrolo[1,2-a]indole derivatives.