Regioselective Sulfonylation of Methylenecyclopropanes with Thianthrenium Salts Enabled by Electron Donor–Acceptor Complex Activation

Herein, we report a catalyst-free sulfonylation of methylenecyclopropanes (MCPs) with thianthrenium salts via electron donor-acceptor complex (EDA) activation, enabling the regioselective functionalization of the unsaturated C═C bond and the three-membered ring unit. The tunable sulfonylation does not require any photocatalysts and generates a series of sulfonyl products in moderate to good yields. Mechanistic experiments indicate that the electron donor-acceptor complexes formed between DABCO and thianthrenium salts are crucial for the trapping of SO₂ as well as the following regioselective sulfonylation of alkene and cyclopropane units of the MCPs.