tert-Butyl Hypochlorite Induced Cyclization of Ethyl 2-(N-Aryl­carbamoyl)-2-iminoacetates

Published as part of the Special Topic Modern Cyclization Strategies in Synthesis

Abstract

Ethyl 2-(N-arylcarbamoyl)-2-iminoacetates can be transformed into the corresponding quinoxalin-2-ones in high yield by using the oxidation system of tert-butyl hypochlorite, tetrabutylammonium iodide and tetrabutylammonium chloride. Oxygen exhibits a beneficial effect on the reaction. The reaction is proposed to follow an iminyl radical cyclization mechanism where azaspirocyclohexadienylperoxyl radical is formed as a key intermediate. The quinoxalin-2-one is derived from the azaspirocyclohexadienylperoxyl radical via concurrent oxygen extrusion and rearrangement.

Key words

cyclization - radical reaction - iminyl radical - quinoxalin-2-ones - oxygen - peroxyl radical

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