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

Abstract

An efficient Rh(III)-catalyzed redox-neutral [4 + 1] annulation between N-aryl phthalazinediones and α,α-difluoromethylene alkynes has been developed for the synthesis of functionalized indazolo[1,2-b]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-b]phthalazine-6,11-diones with quaternary carbon centers.