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Photochemistry of Diethynyl Sulfides:  A Cycloaromatization for the Formation of Five-Membered Rings

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journal contribution
posted on 30.05.2003, 00:00 by Kevin D. Lewis, David L. Wenzler, Adam J. Matzger
The first five-membered ring cycloaromatization reaction has been demonstrated. Photoirradiation of bis(phenylethynyl) sulfide in hexanes/1,4-cyclohexadiene produces 3,4-diphenylthiophene through the presumed intermediacy of 2,5-didehydrothiophene. In addition, phenylacetylene is produced in this reaction consistent with competing direct carbon−sulfur cleavage. For reactions in ethanol or 2-propanol production of the thiophene is accompanied by the formation of phenylacetylene and a thionoester of the corresponding alcohol. Thiophene products also result from the irradiation of other diethynyl sulfides.