Novel One-Pot Three-Component Synthesis of New Ethyl 8-Methyl-3,6-Diphenyl-2,6-Dihydropyrimido[2,1-B][1,3,4]Thiadiazine-7-Carboxylate Derivatives and its Antimicrobial Activities.

A novel series of ethyl 8-methyl-3,6-diphenyl-2,6-dihydropyrimido[2,1-b][1,3,4]-thiadiazine-7- carboxylates 4 (a-m) were synthesized in good to excellent yield via cyclocondensation of 2-amino-5-pheny-6H- 1,3,4-thiadiazine 1 (a-d) with ethyl acetoacetate (2) and various substituted aldehydes 3 (a-d) in presence of ptoluene sulfonic acid (PTSA) in acetonitrile. The structures of these compounds 4 (a-m) were characterized by IR, 1H NMR, 13C NMR, Mass spectroscopic techniques and elemental analysis. All newly synthesized compounds 4 (a-m) were screened for antimicrobial activities.