<i>cis</i> -Selective Direct Halocyclopropanation of Alkenes Mediated by Nucleophilic Cobalt Photocatalysis

High Resolution Image Download MS PowerPoint Slide The cyclopropyl group is an invaluable motif in both medicinal and synthetic chemistry, with 1,2-disubstituted halocyclopropanes serving as important building blocks for the preparation of more complex cyclopropane-containing structures. Herein, we report a Vitamin B 12 -photocatalyzed approach for the direct synthesis of 1,2-disubstituted halocyclopropanes, starting from alkenes and simple haloforms under visible-light irradiation. Our method yields a diverse range of 1,2-disubstituted halocyclopropanes with high cis -selectivity, providing efficient access to these traditionally difficult-to-prepare stereoisomers. Mechanistic studies highlight the crucial role of Vitamin B 12 in influencing the stereochemical outcome of the reaction.