| Summary: | <p>The phototransposition reactions of thiophene- carbonitriles were shown to occur <em>via</em> the intermediate formation and isomerisation of 5-thiabicyclo[2˙1˙0]pent- 2-enes . Thus, irradiation of thiophene-3-carbonitrile in cyclohexane gave 5-thiabieyelo[2˙1˙0]pent-2-ene-2-carbonitrile as the primary photochemical product. Further irradiation produced thiophene-2-carbonitrile. The reaction was reversible, Addition of furan to 5-thiabicyclo[2˙1˙0]pent-2-ene-2- carbonitrile yielded a mixture of <em>exo</em> and <em>endo</em>-10,4-oxa thiatetracyclo[5˙2˙1˙0,sup>2,6</p>˙ 0sup>3,5]dec-8-ene-2-carbonitrile. These two adducts were similarly formed upon irradiation of either thiophene-2 or 3-carbonitrile in furan. <p>[continued in text ...]</p>
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