Organic Photoredox\nCatalytic Difluoroalkylation of\nUnactivated Olefins to Access Difluoro-Containing Tetrahydropyridazines

Herein, we disclose a readily available phenothiazine\nderivative\nas an organocatalyst, which upon excitation with 371 nm light acquires\na strongly reducing power and serves to induce the radical cascade\ndifluoromethylation/cyclization reaction of <i>N</i>-homoallylacetohydrazides.\nA variety of CF<sub>2</sub>COR-tetrahydropyridazines have been obtained\nin moderate to excellent yields. This catalytic platform proceeds\nunder metal-free conditions with a wide substrate scope and broad\nfunctional group compatibility, which unlocks the new reactivity of\nphenothiazine derivatives and adds significant synthetic value to <i>N</i>-heterocycles.