Electrosynthesis of bridged or fused sulfonamides through complex radical cascade reactions: divergence in medium-sized ring formation

Radical cascade addition is one of the most important and efficient strategies for the synthesis of valuable heterocycles with structural diversity and complexity. Organic electrochemistry has emerged as an effective tool for the sustainable molecular synthesis. Herein, we describe an electrooxidative radical cascade cyclization of 1,6-enynes to access two new classes of sulfonamides, containing medium-sized rings. Differences in the activation barrier for radical addition between alkynyl and alkenyl moieties contribute to the chemo-selective addition and regioselective 7- and 9-membered ring-formation. Our finding features good substrate scope, mild conditions, and high efficiency under metal-free and chemical oxidant-free conditions. In addition, the electrochemical cascade reaction allows for the concise synthesis of sulfonamides with bridged or fused ring systems containing medium-sized heterocycles.