Redox-neutral rhodium( <scp>iii</scp> )-catalyzed [4 + 1] annulation of <i>N</i> -aryl phthalazinediones with alkynes

An efficient Rh(III)-catalyzed redox-neutral [4 + 1] annulation between <i>N</i>-aryl phthalazinediones and α,α-difluoromethylene alkynes has been developed for the synthesis of functionalized indazolo[1,2-<i>b</i>]phthalazine-6,11-diones. Notably, α,α-difluoromethylene alkynes function as both C₁ synthons and internal oxidants. This method exhibits a broad substrate scope, excellent chemo-, regio, and stereoselectivity, good functional group tolerance and moderate to high yields. Moreover, this transformation integrates C-H activation, C-C/C-N bond formation, and C-F bond cleavage into a single process, enabling the construction of functionalized indazolo[1,2-<i>b</i>]phthalazine-6,11-diones with quaternary carbon centers.