Synthesis of derivatives of N-(5-(methylsulfanyl)-4H-1,2,4-triazol-3-yl)pyridine-2-amines and their 1,2,4-triazine precursors

A solvent-free interaction between 5-cyano-1.2.4-triazines and 5-methylsulfanyl-4 H -1,2,4-triazol-3-amines has been studied. The structure of the product of ipso -substitution of cyano-group with the corresponding heterocyclic amine residue has been proven by 1Н NMR and ESI-MS data. Thus, in the 1Н NMR spectra a three-proton singlet at 2.61 ppm is present, which can be interpreted as the signal of the methylsulfanyl group protons. Subsequent transformation of 1,2,4-triazine scaffold of the resulting product into a pyridine one has been successfully performed under autoclave conditions. It has been found that methylsulfanyl group undergoes no transformations in both stages of synthesis. This fact is also proven by X-Ray crystallography data of the obtained functionalised bypyridines. According to the X-Ray crystallography data, compound 4 crystallizes as two crystallographically independent molecules in non-centrosymmetric space group P-1 with triclinic system. The crystal structure is formed by numerous intermolecular N∙∙∙H contacts between two crystallographically independent molecules of triazolylpyridine-2-amine. The 1Н NMR spectra of compound 4 contain two doublets of the new pyridine cycle at 7.37 and 7.61 ppm. Thus, properties of 5-methysulfanyl-4 H -1,2,4-triazol-3-amine are different from these of its analogue with mercaptogroup at C5 position. Namely, in accordance to our previous results ipso -substitution of C5-cyanogroup of 1,2,4-triazine with moiety of the latter amine is accompanied by desulfurization reaction.