Modular Enantioselective Synthesis of -Cyclopropanes through Self-Sensitized Stereoselective Photodecarboxylation with Benzothiazolines.

Chiral -cyclopropanes are strained rigid analogues of alkyl chains, whose study and application are limited by their difficult synthesis. A modular approach from olefin materials is enabled by the discovery of the electron donor-acceptor (EDA) interaction between 2-substituted benzothiazolines and -hydroxyphthalimide esters. These complexes are activated by visible light without photocatalysts, and the benzothiazoline reagent plays a triple role as a photoreductant, a stereoselective hydrogen-atom donor, and a Brønsted acid. Beyond the enantioselective synthesis of -cyclopropanes, these results introduce benzothiazolines as accessible and easily tunable self-sensitized photoreductants.