Visible light-mediated cyclopropylamide [3+2] cycloaddition with maleimides to synthesize cyclopentylamide derivatives

The [3+2] cyclization is one of the most common reactions for constructing five-membered rings. In this study, we present a detailed synthetic methodology of [3+2] cyclization of <i>N</i>-acyl cyclopropylamines and <i>N</i>-substituted maleimides photocatalyzed by 9-mesityl-10-methylacridinium perchlorate. A series of stable <i>N</i>-acyl cyclopentylamine derivatives were prepared under mild conditions.