Synthesis and Biological Evaluation for Antihistaminic activity of N¹-Alkyl– 2(N⁴-Alkyl/Aryl piperazinyl methyl) Benzimidazole derivatives

Benzimidazole derivatives are known for their wide spread pharmacological activities and benzimidazole derived antihistaminics are more widely used group of therapeutic agents in allergic diseases because of their low toxicities. As a part of ongoing effort finding novel Antihistaminics, several N¹, 2-substituted benzimidazole derivatives were synthesized and screened for their antihistaminic potential. O-fluoro nitrobenzene condensed with alkyl amines and these condensation products were hydrogenated to get N¹-alkyl-o-phenylene diamines. Condensation of substituted ophenylene diamines with chloro acetic acid gives cyclised intermediates and these intermediates when condensed with N¹-alkyl/aryl piperazines gives variously substituted piperazinyl benzimidazole derivatives.

The synthesized N¹-Alkyl–2(N⁴-Alkyl/Aryl piperazinyl methyl) Benzimidazole derivatives were screened for antihistaminic activity using Chlorpheniramine maleate (CPM) as reference standard. Interestingly, few synthesized compounds exhibited slight to moderate antihistaminic activity. Based on results obtained we can conclude that these molecules hold potential for further modification as selective Antihistaminics for H¹receptor.