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Paper | Regular issue | Vol 26, No. 5, 1987, pp.1313-1322
Published online, 1st January, 1970
DOI: 10.3987/R-1987-05-1313
Photochemical and Thermal Reactions of Heterocycles. IV. Phooto-oxidation Reactions of Mesoionic Dithioliumolate, Thiazoliumolate, and Related Heterocycles. Solvent Effects of the Course of the Photo-oxidation

Hiroshi Kato, Kazue Tani, Haruki Kurumisawa, and Yoshiko Tamura

*Department of Chemistry, Faculty of Science, Shinshu University, Asahi, Matsumoto 390-8621, Japan

Abstract

Photo-oxidation of mesoionic 1,3-dithiolium-4-olates (1) gave diacyl disulfide (2), and that of a mesoionic thiazolium-4-olate (6) and oxazolium-5-olate (9) gave diacylamides as the main products. The formation of these products was rationalized by a route involving fragmentation of the corresponding endoperoxides, which are formed by cycloaddition of singlet oxygen on the mesoionic rings. Photo-oxidation of 5(4H)-oxazolones (12) and a 5(4H)-thiazolone (17) in dichloromethane gave the corresponding dehydro-dimers, while that of the former in dimethylformamide gave mainly diacylamides. The acylamides were considered to arise via the endoperoxides of the mesoionic tautomers.