Cycloaddition reactions of azides with electron-poor olefins : Isomerization and thermolysis of the resulting Δ 2-triazolines

Abstract

The cycloaddition reactions of phenyl azide and butyl azide with monosubstituted electronpoor olefins are highly regioselective (if not regiospecific) and lead to 1,4-disubstituted Δ 2-triazolines or products derived therefrom: aziridines, diazocompounds, pyrazolines and 1,4-trisubstituted triazolines. As expected, the latter three products are not formed when a methyl group is introduced in the geminal position of the olefins, but Δ 2-triazolines and aziridines are then obtained exclusively. In all cases studied the 1,4-substituted Δ 2-triazolines derived from phenyl azide only give aziridines on thermolysis, whereas those derived from alkyl azides are thermally converted into a mixture of aziridine and enamine.