EVALUATION OF SOME ANTIINFLAMMATORY PYRIMIDOBENZIMIDAZOLES SYNTHESIZED VIA NOVEL TIN(II) CHLORIDE HYDROCHLORIC-ACID ASSISTED WATER ADDITIONAND REDUCTION OF -(2-NITROARYL)-1,4-DIHYDROPYRIMIDINE-2(3H)-THIONES

-(2-nitroaryl)-1,4-dihydropyrimidine-2(3H)-thiones (Ia-c) on reduction with Al/Hg amalgam gave ,4,6-trimethyl-1,4-dihydropyrimidine-2(3H)-th iones (IIa-c). The reduction of 4,4,6-trimethyl-1-(2-nitroaryl or 4-ni trophenyl or phenyl)-1,4-dihydropyrimidine-2(3H)-thiones Ia-f) with Sn Cl2/HCl gave 1-(2-aminoaryl or 4-aminophenyl or imethyl-1,4,5,6-tetrah ydropyrimidine-2(3H)-thiones (IIIa-f). 1-(2-Aminoaryl)-6-hydroxy-4,4,6 -trimethyl- 1,4,5,6-tetrahydropyrimidine-2(3H)-thiones (IIIa-d) underg o cyclization to give pyrimido[3,4-a]benzimidazoles IVa-d when refluxe d for 2 h in ethanol using a catalytic amount of sulfuric acid. Pyrimi do[3,4-a]benzimidazole IVa undergoes S-alkylation when treated with et hylbromo-acetate to give S-alkylated pyrimido[3,4-a]benzimidazole VI. nyl)-6-hydroxy-4,4,6-trimethyl-1,4,5,6-tetrahydro- pyrimidine-2(3H)-th ione (IIIe) on stirring at r.t. with ethanol and a catalytic amount of sulfuric acid gave 1-(4-aminophenyl)-6-ethoxy-4,4,6-trimethyl-1 ,4,5, 6-tetrahydropyrimidine-2(3H)-thione (V). Compounds IIIa,b,c, IVa-d and VI were tested for anti-inflammatory activity, IIIa,b,c, IVa and VI w ere inactive, whereas IVb and IVc showed 14% and 34% activity, respect ively, at 100 mg/kg p.o. Compound IVc showed 28% activity at 25 mg/kg p.o. which is almost equipotent to phenylbutazone (30 mg/kg p.o.).