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

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