Vinylindenes and some heteroanalogues in the Diels-Alder reaction. IV. Reactions of ethenetetracarbonitrile with some 3-vinylindoles

Abstract

3-Vinylindoles are conveniently prepared from methylenetriphenylphosphorane and indole-3-carbaldehydes. Those studied give normal Diels-Alder adducts with ethenetetracarbonitrile, except in the case of the 2-methyl derivative, where steric hindrance results in formation of a cyclobuty-indole. The adducts are relatively unstable, and decompose rapidly to indolylbutadienetricarbonitriles.