Synthesis of Quinoxalines through Cu-electrocatalytic Azidation/Annulation Cascade at Low Catalyst Loading

Abstract

A Cu-electrocatalytic azidation of N -aryl enamines and subsequent denitrogenative annulation for the construction of quinoxaline frameworks is reported. Only 0.5 mol % of copper(II) chloride was employed for this cascade transformation displaying excellent functional-group compatibility even with complex bioactive scaffolds. The efficient electro-oxidative protocol enables the use of NaN 3 as the cheapest azide source. Detailed mechanistic experiments, cyclic voltammetry, and spectroscopic studies provided strong evidence for a dual role of the Cu catalyst in azidyl and iminyl radical generation steps.

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