Organic Photoredox Catalytic Difluoroalkylation of Unactivated Olefins to Access Difluoro-Containing Tetrahydropyridazines

Herein, we disclose a readily available phenothiazine derivative as an organocatalyst, which upon excitation with 371 nm light acquires a strongly reducing power and serves to induce the radical cascade difluoromethylation/cyclization reaction of N-homoallylacetohydrazides. A variety of CF₂COR-tetrahydropyridazines have been obtained in 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 value to N-heterocycles.