Vinylindenes and Some Heteroanalogues in the Diels-Alder Reaction. VI. Vinylbenzo[b]thiophens and Ethenetetracarbonitrile

Abstract

3-Vinylbenzo[b]thiophen and three simple homologues are shown to give normal Diels-Alder adducts with ethenetetracarbonitrile, whereas the 3-methyl-2-vinyl- and 2-methyl-3-prop-1'-enyl derivatives give cyclobutanes. 2-Methyl-3-vinylbenzo[b]thiophen and ethenetetracarbonitrile give an adduct resulting from reaction of a tautomeric form of the diene, but a naphthalene analogue and a phenanthrene analogue of this substituted benzothiophen give normal adducts.