ABSTRACT
Many researchers have modified this protocol for the preparation of various heterocyclic systems such as naphtho-, benzo- and heterocycle-fused indazolone derivatives. Analogous N-containing substrates have also been used for the generation of a wide range of heterocyclic compounds. The positions of the nucleophile and the diimine species can be exchanged for feasible cascade synthesis of analogous heterocyclic compounds. Heterocyclic compounds, by virtue of their specific activities, can be employed in the treatment of infectious diseases. Review of literature indicates that nitrogen-containing heterocycles find a significant place in the development of pharmacologically important molecules. There has been a growing interest in the synthesis of benzimidazole-based heterocycles. There are a number of practically important routes to benzimidazole-based polyheterocycles – reactions between benzaldehyde derivatives and benzimidazoles containing an activated methylene group at position 2, coumarins and o-phenylenediamines, 2-azidoanilines and substituted cinnamaldehydes, 2-(2-aminoaryl(hetaryl))benzimidazoles and haloketones, o-phenylenediamines and phthalic anhydrides, 2-(hydroxymethylene)-3-keto steroids and functionalized benzimidazoles.
