Selenium-Containing heterocycles from isoselenocyanates: synthesis of 5-Amino-2,4-dihydro-3H-1,2,4-triazole-3-selones

The reaction of S-methylisothiosemicarbazide hydroiodide (= S-methyl hydrazinecarboximidothioate hydroiodide; 1), prepared from thiosemicarbazide by treatment with MeI in EtOH, and aryl isoselenocyanates 5 in CH2Cl2 affords 3H-1,2,4-triazole-3-selone derivatives 7 in good yield (Scheme 2, Table 1). During attempted crystallization, these products undergo an oxidative dimerization to give the corresponding bis(4H-1,2,4-triazol-3-yl) diselenides 11 (Scheme 3). The structure of 11a was established by X-ray crystallography