Synthesis and properties of 5(4,6-diphenyl-2-pyrimidin-2-yl)-1,2,4-triazolin-3-thione and derivatives

By treatment of 4,6-diphenyl-pyrimidin-2-carboxyl chloride (1) with thiosemicarbazide the acylthiosemicarbazide 3 has been synthesized. Compound 3 could also be obtained by action of hydrazide on potassium thiocyanate. 5-(4,6-Diphenyl-pyrimidin-2-yl)-1,2,4-triazolin-3-thione (5) could be prepared either by basecatalyzed cyclization of acylthiosemicarbazide or by the reaction of methyl 4,6-diphenyl-pyrimidin-2-carboxylate with thiosemicarbazide in the presence of sodium methoxide. Alkylation of the 1,2,4-triazolin-3-thione 5 with chloroacetic acid resulted in formation of the S-carboxymethyl derivative 6. On heating, with a mixture of glacial acetic acid/acetic anhydride, compound 6 afforded 6-(4,6-diphenyl-pyrimidin-2-yl)thiazolo[3,2-b]-1,2,4-triazol-3(2H) -one (7). Condensation of 7 with aromatic aldehydes yielded 2-arylidene-6-(4,6-diphenyl-pyrimidin-2-yl)thiazolo[3,2-b]-1,2,4-+ ++triazol-3(2H)-ones, which could also be prepared by treatment of the S-carboxymethyl derivative 6 with an appropriate aldehyde in the presence of acetic acid and acetic anhydride. Some of the synthesized compounds possess a weak antiinflammatory activity.