Synthesis of Functionalized Cyclopropanes from Carboxylic Acids by a Radical Addition–Polar Cyclization Cascade

Abstract Herein, we describe the development of a photoredox‐catalyzed decarboxylative radical addition–polar cyclization cascade approach to functionalized cyclopropanes. Reductive termination of radical–polar crossover reactions between aliphatic carboxylic acids and electron‐deficient alkenes yielded carbanion intermediates that were intercepted in intramolecular alkylations with alkyl chlorides appended to the alkene substrate. The mild conditions, which make use of a readily available organic photocatalyst and visible light, were demonstrated to be amenable to a broad range of structurally complex carboxylic acids and a wide variety of chloroalkyl alkenes, demonstrating exquisite functional group tolerance.