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

Herein, we describe the development of a photo-redox-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.