Vilsmeier–Haack reaction of 7-acetyl-2-arylindoles: a convenient method for the synthesis of 6-oxo-6H-pyrrolo[3,2,1-ij]quinoline-1,5-dicarbaldehydes

Abstract

A simple and efficient method for the one-pot synthesis of novel 6-oxo-6H-pyrrolo[3,2,1-ij]quinoline-1,5-dicarbaldehydes via the Vilsmeier–Haack reaction of the corresponding 7-acetyl-2-arylindoles has been developed. The mechanism of this reaction is envisaged to involve initial C-3 formylation and subsequent diformylation at the acetyl group with the excess Vilsmeier–Haack reagent followed by heteroannulation of the six-membered ring with concomitant extrusion of dimethylamine to afford the 1,2,5,8-tetrasubstituted pyrroloquinolinones. The highlight of this method is the construction of carbon–carbon and carbon–nitrogen bonds in a single-pot operation to afford polycarbo-substituted pyrroloquinolinones.