Abstract In research of new biologically active compounds, the reactions of amino-pyrazin-2- hydrazide and methylhydrazide with isothiocyanates, aromatic aldehydes, ketones, CS 2, and formic acid were made. New thiosemicarbazides, 1, 3, 4-thiadiazoles, 1, 3, 4- oxadiazoles, and 1, 2, 4-triazoles were obtained. New 4-oxopteridine derivative 26 was also synthesized.