Reversal of regioselectivity in reactions of donor–acceptor cyclopropanes with electrophilic olefins

Reactivity of donor-acceptor cyclopropanes towards nucleophiles and electrophiles is determined by the specific philicity of the carbon atoms originating from the strong polarization of the central C-C bond. Herein, we report that vitamin B12 catalysis enables the transformation of an initially electrophilic center into a nucleophilic radical that reacts with SOMOphiles. This radical-based strategy reverses the standard regioselectivity and thus complements the classical approaches.