Synthesis of A Novel Heterocyclic System of 3,8-Disubstituted-5H-Pyrimido[5’,4’:5,6][1,4]Thiazino[3,2-e][1,2,4]Triazine

Abstract

The new compounds 6-methyl-8-morpholino-2H pyrimido[5’,4’:5,6][1,4]thiazino[3,2e][1,2,4]triazin-3(5H)-one (3a) and 6-methyl-8-(piperidin-1-yl)-2Hpyrimido[5’,4’:5,6][1,4]thiazino[3,2-e][1,2,4]triazin-3(5H)-one (3b) were obtained from cyclocondensation of 6-bromo-1,2,4-triazine-3,5(2H,4H)-dione (1) with appropriate 5-amino-6methylpyrimidine-4-thiol (2a, b) in dimethylformamide and in the presence of potassium carbonate under reflux. Reaction of compounds (3a, b) with phosphorous oxychloride gave 4-(3-chloro-6-methyl-5H-pyrimido[5’,4’:5,6][1,4]thiazino[3,2-e][1,2,4]triazin-8-yl)morpholine (4a) and 3-chloro-6-methyl-8-(piperidin-1-yl)-5H-pyrimido[5’,4’:5,6][1,4]thiazino[3,2-e][1,2,4]triazine (4b). Nucleophilic substitution of chlorine atom of compounds (4a, b) with typical secondary amines in DMF and K2CO3 produced the new derivatives of the 3,8-disubstituted-5H-pyrimido[5’,4’:5,6][1,4]thiazino[3,2-e][1,2,4]triazine ring systems (5a–f). All the synthesized products were characterized and confirmed by their spectroscopic and microanalytical data.