Unveiling Vinyl Radical–Ketone Coupling: Synthesis of Flavan-3-ols via β-Scission Suppression

An unprecedented vinyl radical–ketone coupling has been achieved via intramolecular, metal- and oxidant-free cyclization, enabling direct C–C bond formation under superbasic conditions while preserving the alkene unit. This transformation overcomes a long-standing challenge in radical chemistry by enabling a pathway that avoids the rapid β-scission typically associated with alkoxy radicals. The reaction proceeds under operationally simple conditions to afford benzylidene flavan-3-ols in a single step, with a broad structural scope and broad functional group compatibility. Mechanistic insights were gained through the synthesis of deuterium-labeled analogues. Late-stage functionalization with bioactive drug molecules further highlights the synthetic utility of this methodology.