Synthesis of 2-Imino-1,3,4-Selenadiazoles via Tributylphosphine-Mediated Annulation of N-Aroyldiazenes with Isoselenocyanates

2-Imino-1,3,4-selenadiazole derivatives can be synthesized from hydrazides and isoselenocyanates by sequential oxidation and a tributylphosphine (PBu3)-promoted annulation reaction at room temperature. In this synthetic process, crude less stable N-aroyldiazene intermediates generated by I-2-mediated oxidation of hydrazides were used directly in a subsequent annulation reaction to afford the selenadiazole products. The merits of the present synthetic strategy also include absence of transition metals and gram-scale synthesis.