Visible‐Light Photoredox‐Catalyzed Tandem One‐Pot Construction of C4‐Difluoroalkylated Phthalazin‐1(2H)‐Ones

Tandem one-pot regioselective synthesis of C4-difluoroalkylated phthalazin-1(2H)-ones from readily available hydrazines, 2-formylbenzoic acids and bromodifluoroacetate derivatives under visible-light photocatalysis is reported. This mild protocol provides straightforward access to various C4-difluoroalkylated phthalazin-1(2H)-ones, and displays broad substrate scope and wide functional group tolerance. Moreover, this process is also suitable for the synthesis of C4-trifluoromethylated and perfluorobutylated phthalazin-1(2H)-ones. The use of fac-[Ir(ppy)(3)] photocatalyst and the introduction of an organic base additive are pivotal to catalysis.