Syntheses of 3H-1,2,4-triazol-3-ones by copper-promoted oxidative N-N bond formation of amidines with isocyanates

This study presents an efficient strategy for constructing 3H-1,2,4-triazol-3-ones via a copper-promoted [3 + 2] annulation reaction of amidine hydrochlorides and isocyanates. This transformation may undergo nucleophilic attack of amidines on isocyanates and copper promoted intramolecular N-N oxidative coupling. Various amidine hydrochlorides and isocyanates are well tolerated, providing the target products with acceptable yields. The advantages of this procedure include cheap raw materials, high atom economy and easy operation.