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Paper | Regular issue | Vol 48, No. 1, 1998, pp.61-69
Published online, 1st January, 1970
DOI: 10.3987/COM-97-8000
Thermolysis of Selenophene 1,1-Dioxides

Takashi Umezawa, Tomoki Matsui, Yoshiaki Sugihara, Akihiko Ishii, and Juzo Nakayama*

*Department of Chemistry, Faculty of Science, Saitama University, Saitama, Saitama 338-8570, Japan

Abstract

Selenophene 1,1-dioxides are thermally far labile than the corresponding thiophene 1,1-dioxides. Even heavily substituted tetraphenylselenophene 1,1-dioxide (1a) decomposed, by a process not involiving cyclodimerization, when heated above its melting point or heated in refluxing toluene. Thus, the thermolysis of 1a in refluxing toluene afforded tetraphenylselenophene (2a, 6%), tetraphenylfuran (3a, 71%), (Z)-1,2,3,4-tetraphenyl-2-butene-1,4-dione (Z-4a, 19%), (E)-1,2,3,4-tetraphenyl-2-butene-1,4-dione (E-4a, 4%), SeO2 (23%), and Se (22%), while that of the neat sample gave 2a (5%), Z-4a (78%), E-4a (17%), SeO2 (17%), and Se (29%). Similar results were also obtained on thermolyses of a series of selenophene 1,1-dioxides. The experimental observations (influence of solvents, oxygen, and additive such as diene to the decomposition rate and the presence of induction period) revealed that the mechanism of the decomposition is highly complex. A tentative mechanism that can explain the observed products is presented.