Synthesis and biological evaluation of benzo[d]imidazolyl chromeno[2,3-d]pyrimidinones

A series of benzo[d]imidazolyl chromeno[2,3-d]pyrimidnones were described. The key intermediate 2-cyano-N-(2-mercapto-1H-benzo[d]imidazol-5-yl)acetamide (3) is obtained by reacting 5-amino-2-mercaptobenzimidazole (1) with ethyl cyanoacetate (2). Compound 3 on reaction with substituted salicylaldehydes afforded 2-imino-N-(2-mercapto-1H-benzo[d]imidazol-5-yl)-2H-chromene-3-carboxamides (5) in good yields. Compounds 5 on condensation with formalin furnished the title compounds viz., 3-(2-mercapto-1H-benzo[d]imidazol-5-yl)-2H-chromeno[2,3-d]pyrimidin-4(3H)-ones (7). All the synthesized compounds were screened for their anti-microbial and anti-oxidant activities.