Amine-Enabled Electron Donor-Acceptor Complex Catalysis for Cyclopropanation.

Electron donor-acceptor (EDA) complexes have emerged as a powerful catalyst-free platform for visible-light-driven radical transformations. Herein, we report an amine-enabled EDA-mediated cyclopropanation of alkenes formed through a ground-state charge-transfer complex between diiodomethane and amine. The method proceeds under mild conditions and exhibits broad functional-group tolerance. The comprehensive mechanistic investigations, including EPR spectroscopy, cyclic voltammetry, UV-Vis analysis, quantum yield determination, and DFT studies, support an EDA-mediated radical pathway.