Rh(III)-Catalyzed [4 + 2] Annulation of Indoles with Diazo Compounds: Access to Pyrimido[1,6‑a]indole-1(2H)‑ones

The Rh­(III)-catalyzed regioselective C2–H bond carbenoid insertion/cyclization of N-amidoindoles with α-acyl diazo compounds has been developed. This method provides a novel approach to 2H-pyrimido­[1,6-a]­indol-1-ones with a broad range of functional group tolerance. The synthetic utilities of the approach are demonstrated by versatile chemical transformations.