Photoredox-catalyzed cyclopropanation of allenes towards vinyl-cyclopropanes.

While the vinyl cyclopropane (VCP) scaffold exhibits unique reactivity in chemical transformations, its synthesis presents certain challenges. Herein, we report the visible-light photoredox-catalyzed radical-polar crossover cyclization (RPCC) of terminal and internal allenes with carboxylic acids, realizing the construction of functionalized vinyl cyclopropanes (VCPs) with highly chemo-, and regioselectivities under mild conditions. Moreover, this photoredox protocol exhibits good functional group tolerance, a broad substrate scope, facile scalability and easy rearrangement to give various cyclopentene units.