Intramolecular Reductive Amidation of Unactivated Esters with Nitroarenes: A Telescoped Synthesis of Tetrahydropyrrolo/Pyrido[1,2- a ]quinoxalinones.

A reductive amidation of unactivated esters with nitroarenes, a key step in the telescopic synthesis of tetrahydropyrrolo[1,2- a ]quinoxalinones and tetrahydropyrido[1,2- a ]quinoxalinones, is reported. The process involves an intermolecular base-mediated S N Ar reaction, followed by intramolecular reductive amidation employing sodium dithionite. The substrate scope coupled with the demonstration of the synthesis of pharmaceuticals is reported. The key features include nitro reduction at room temperature, easy purification without chromatography, amidation of unactivated esters without any externally added activating agent, and a telescopic process.