Synthesis of Novel Fused Heterocyclic Compounds from 7-amino-[1,2,4]triazino[3,4- b][1,3,4]thiadiazine-8-carbonitrile

A one-pot synthesis of 7-amino-4-oxo-3-(2-(2-thienyl)vinyl)-4,8-dihydro-[1,2,4]triazino[3,4-b][1,3,4]thiadiazine-8- carbonitrile (2) via the reaction of 4-amino-3-sulfanyl-6-[2-(2-thienyl)vinyl]-1,2,4-triazin-5(4H)-one (1) with bromomalononitrile is described. The formation of the new fused heterobicyclic and heterotricyclic nitrogen systems ([1,2,4]triazino[3,4-b][1,3,4]thiadiazin-7- yl)guanidine 3, pyrimido[4,5-e][1,2,4]triazino[3,4-b][1,3,4]thiadiazin-4-one 5, [1,2,4]triazino[3,4-b][1,3,4]thiadiazin-7-ylcarbamodithioic acid 6, pyrimido[4,5-e][1,2,4]triazino[3,4-b][1,3,4]thiadiazin-4-one 8, [1,2,4]triazino[3,4-b][1,3,4]thiadiazin-7-ylformimidate 9, pyrido[2,3-e][1,2,4]triazino[3,4-b][1,3,4]thiadiazine-9-carbonitrile 11, (pyrimido[4,5-e][1,2,4]triazino[3,4-b][1,3,4]thiadiazin-8-yl) acetonitrile 12 and pyrimido[4,5-e][1,2,4]triazino[3,4-b][1,3,4]thiadiazine-4,10(10aH)-dione 13 was achieved by treating 2 with cyanamide, urea, thiourea, CS2 and ethanolic ethoxide, formamide, triethyl orthoformate, malononitrile, ethyl cyanoacetate and chloroacetyl chloride, respectively. Additionally, the 8-thiourea and 8-acetamide derivatives 16a,b, 18 and 19 were synthesized by reacting 2 with various isothiocyanate derivatives and acetic anhydride. The structures of all synthesized compounds were deduced by elemental analysis, mass spectrometry and analysis of their spectral data (IR, 1H NMR, 13C NMR).