New Alkene Cyclopropanation Reactions Enabled by Photoredox Catalysis via Radical Carbenoids

We describe the recent emergence of a new approach for the synthesis of cyclopropane rings by means of photoredox catalysis. This methodology relies on the photocatalytic generation of radical carbenoids or carbenoid-like radicals as cyclopropanating species, and is characterized by excellent functional group tolerance, chemoselectivity and the ability to form cyclopropanes with excellent control from E/Z alkene mixtures. The mild reaction conditions and employment of user-friendly reagents are highly attractive features that may lead to this approach being used in academic and industrial laboratories.