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Note | Regular issue | Vol 55, No. 12, 2001, pp.2423-2430
Published online, 1st January, 1970
DOI: 10.3987/COM-01-9358
■ An Improved Method for the Preparation of 4,7-Dioxo-4,7-dihydrobenzo[b]thiophene-2-carboxylates from 2-Acyl-1,4-benzoquinones and Mercaptoacetates

Kazuhiro Kobayashi,* Keiichi Yoneda, Masaharu Uchida, Hideki Matsuoka, Osamu Morikawa, and Hisatoshi Konishi

*Department of Materials Science, Faculty of Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

4,7-Dioxo-4,7-dihydrobenzo[b]thiophene-2-carboxylates (4) have been synthesized in a one-pot procedure from 2-acyl-1,4-benzoquinones (1) and mercaptoacetates (2) by using 1-trimethylsilylimidazole as a protective reagent as well as a base. Thus, reaction of 1 with 2 in THF at room temperature was followed by treatment with excess of 1-trimethylsilylimidazole at 80 °C. Then the cooled mixture was hydrolyzed with hydrochloric acid and oxidized with cerium(IV) ammonium nitrate (CAN) to give the expected thiophenequinone derivatives (4). 4,9-Dioxo-4,9-dihydronaphtho[2,3-b]thiophene-2-carboxylates (7) were similarly prepared from 2-acyl-1,4-naphthoquinones (5) and mercaptoacetates, in general, by omitting the CAN oxidation procedure.