Synthesis of Cyclic Azomethine Imines by Cycloaddition Reactions of N‑Isocyanates and N‑Isothiocyanates

Various nitrogen-substituted iso­(thio)­cyanates engage in [3 + 2]-cycloaddition reactions to form azomethine imines containing triazolone, triazole–thione, and pyrazole–thione cores. First, iminoisothiocyanates are shown to undergo aminothiocarbonylation reactions with strained alkenes, and a comparison with recently reported reactions of iminoisocyanates highlights their reduced reactivity. In contrast, amino­(thio)­carbonylation reactions of imines with iminoisocyanates and iminoisothiocyanates proved more efficient, providing access to triazolone and triazole–thione cores. The dipole products can be converted to valuable heterocyclic cores through simple derivatization reactions.