Reactions of nitroso hetero-Diels-Alder cycloadducts with azides: stereoselective formation of triazolines and aziridines.

The addition of azides to acylnitroso hetero-Diels-Alder cycloadducts derived from cyclopentadiene affords exo-triazolines in excellent yield. The reaction is greatly affected by the level of alkene strain, while sterically demanding azides do not hinder the reaction. Conversion of the triazolines to aziridines is also described.