Novel aspects of the reaction of 3-(benzimidazol-2-yl)-2-iminocoumarins with aromatic aldehydes

Article abstract of DOI:10.1023/B:COHC.0000028630.64934.8c

The reaction of 3-(benzimidazol-2-yl)-2-iminocoumarins with aromatic aldehydes has been studied. The condensation products 7-aryl-7H-benzo[4,5] imidazo[1,2-c]benzopyrano[3,2-e]pyrimidines or 3-(benzimidazol-2-yl)coumarins are formed depending on the nature of the substituent in the starting 2-iminocoumarin and aldehyde. In DMF medium, 7-aryl-7H-benzo[4,5]imidazo[1,2-c] benzopyrano[3,2-e]pyrimidines isomerize to the corresponding 7-aryl-14H-benzo[4,5]imidazo[1,2-c]benzopyrano-[3,2-e]pyrimidines. The effect of the substituent on the isomerization process has been studied and the reaction mechanisms are discussed.