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Synthesis 1994; 1994(11): 1175-1180
DOI: 10.1055/s-1994-25667
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Evaluation of Some Anti-Inflammatory Pyrimidobenzimidazoles Synthesized via Novel Tin(II) Chloride-Hydrochloric Acid Assisted Water Addition and Reduction of 4,4,6-Trimethyl-1-(2-nitroaryl)-1,4-dihydropyrimidine-2(3H)- thiones

Sham M. Sondhi* , Archana Magan, Rajesh Sahu, Vijendra K. Mahesh, Rakesh Shukla, Gyanendra K. Patnaik
  • *Department of Chemistry, University of Roorkee, Roorkee-247667, India
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Publication Date:
25 April 2002 (online)

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4,4,6-Trimethyl-l-(2-nitroaryl)-1,4-dihydropyrimidine-2(3H)-thiones (Ia-c) on reduction with Al/Hg amalgam gave 1-(2-aminoaryl)-4,4, 6-trimethyl-1,4-dihydropyrimidine-2(3H)-thiones (IIa-c) . The reduction of 4,4,6-trimethyl-1-(2-nitroaryl or 4-nitrophenyl or phenyl)-1, 4-dihydropyrimidine-2(3H)-thiones (Ia-f) with SnCl2/HCl gave 1-(2-aminoaryl or 4-aminophenyl or phenyl)-6-hydroxy-4,4, 6-trimethyl-1,4,5,6-tetrahydropyrimidine-2(3H)-thiones (IIIa-f). 1-(2-Aminoaryl)-6-hydroxy-4,4,6-trimethyl-1,4,5,6-tetrahydropyrimi-dine-2(3H) -thiones (IIIa-d) undergo cyclization to give pyrimido[3,4-a]benzimidazoles IVa-d when refluxed for 2 h in ethanol using a catalytic amount of sulfuric acid. Pyrimido[3,4-a]benzimidazole IVa undergoes S-alkylation when treated with ethylbromo-acetate to give S-alkylated pyrimido[3,4-a]benzimidazole VI. 1-(4-Aminophenyl)-6-hydroxy-4,4,6-trimethyl-1,4,5,6-tetrahydro-pyrimidine-2 (3H)-thione (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 were inactive, whereas IVb and IVc showed 14% and 34% activity, respectively, 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.).