Organic Photoredox Catalytic Sulfonylation of Enaminones to Access 3‐Sulfonyl Chromones

Herein, we disclose a readily available phenothiazine derivative as an oxidizing organic photocatalyst, that serves to induce radical cascade sulfonylation/cyclization reaction of enaminones. A variety of 3‐sulfonyl chromones have been obtained with moderate to excellent yields. This catalytic platform proceeds under metal‐free conditions with a wide substrate scope and broad functional group compatibility, which unlocks the new reactivity of phenothiazine derivatives and adds significant synthetic values to <i>O</i>‐heterocycles.