Facile Synthesis of [1,2,4]Triazolo[4,3-a]pyrazin-3-amines via Oxidative Cyclization of 1-(Pyrazin-2-yl)guanidine Derivatives

In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3- a ]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3- a ]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3- a ]pyrazin-3-amines, and then elucidated their structures based on their 1 H-NMR, 13 C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.