Mechanochemical Synthesis of 1,2,4‐Triazoles via a [3+2] Cycloaddition of Azinium‐N‐Imines and Nitriles.

We report here a mechanochemical Cu‐catalyzed [3+2] cycloaddition of azinium‐N‐imines with nitriles under solventless grinding conditions. Various 1,2,4‐triazolos derivatives were obtained in 51–80% yields. The developed protocol offers advantages in functional‐group compatibility, scalability, no use of solvents, shorter reaction time, and without external heating. In addition, heterocyclic N‐imines such as quinolinium and isoquinolinium salts are also suitable substrates, resulting in the production of 1,2,4‐triazolo[1,5‐a]quinoline and 1,2,4‐triazolo[5,1‐a]isoquinoline derivatives under mechanochemical conditions. [ABSTRACT FROM AUTHOR]