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Paper | Regular issue | Vol 65, No. 7, 2005, pp.1589-1600
Published online, 25th April, 2005
DOI: 10.3987/COM-05-10382
Synthesis of Quinoxaline 1,4-Dioxides from 5,6-Diethylbenzofuroxan on Silica Gel

Nobuo Sekimura, Hiroaki Saito, Shinichi Miyairi, and Tohru Takabatake*

*College of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi-shi, Chiba 274-8555, Japan

Abstract

5,6-Diethylbenzofuroxan (1) and 5-ethylbenzofuroxan (2) were synthesized in good yield via oxidation of o-nitroanilines by sodium hypochlorite. 4-Ethylbenzofuroxan (3) was prepared by the photochemical decomposition of 2-ethyl-6-nitrophenyl azide (3N). 1H-NMR spectrum showed that the compound (3) rapidly rearranges between the two unsymmetrical bicyclic structures at 296.8 K. The 4-ethyl group may possibly function as a barrier against molecular rearrangement. Quinoxalines yields depended on the enol content in β-keto esters or 1,3-diketones. A comparison of the reactivity of 1 with benzoylacetone was made with that of other benzofuroxans. The reaction of 1 condensed with the carbonyl compound better than other benzofuroxans.