Comparative studies on conventional and microwave assisted synthesis of benzimidazole and their 2-substituted derivative with the effect of salt form of reactant

Benzimidazole and their derivative were reported to have wide biological activities and were synthesized by using different solvents and ring closing agents. The present work deals with the comparative synthesis of 2-alkyl and aryl substituted benzimidazole derivative in the presence of polyphosphoric acid through microwave and conventional methods and also studied the effect of salt form of reactant for completion of the reaction. The 2-substituted aryl and alkyl benzimidazole derivative were synthesized via microwave and was observed to be more beneficial, in respect of yield (increases up to 10 to 50%) and time (96 to 98% was reduced) than conventional method of synthesis. This study was concluded that the salt form of reactant (o-phenylenediamine dihydrochloride) gave reduced colour impurities, homogenous mixing and reduced time for completion of reaction.