Abstract

FACILE AND EFFICIENT ONE-POT SYNTHESIS OF BENZIMIDAZOLES USING LANTHANIDE TRIFLATE CATALYST

^V. Prabhakar*, ^K. Sudhakar Babu, ^L.K. Ravindranath, +J. Latha

ABSTRACT

Direct one-step synthesis of various benzimidazoles from phenylenediamines and aldehydes is described using lanthanum triflate as the catalyst. The salient features of this method include a simple procedure, mild conditions, no coupling agents or commercial oxidants/ additives used,Re usable catalyst, no waste produced easy purification, and high Purity. Results: We have examined the effect of different solvents using the same reaction conditions. The yield of the product changed with the nature of the solvents, and better conversion and easy isolation of products were found with Aceto nitrile. In a similar manner, the reaction with o-phenylenediamine and 4-hydroxy-3-methoxybenzaldehyde (vanillin) was carried out without any solvents. The observation shows that the reaction was not brought into completion, even after starting for a period of 9 h, and the reaction mixture showed a number of spots in thin-layer chromatography. Conclusions: In conclusion, lanthanum triflate has been employed as a novel and efficient. Catalyst for the synthesis of benzimidazoles in good yields from o-phenylene diamine and a wide variety of aldehydes. All of the reactions were carried out in the presence of lanthanum triflate (10 mol%) in aceto nitrile,water(2:1) at room temperature.

Keywords: Benzimidazoles; Heterocycle; Aldehydes; lanthanum triflate; Simple procedure; Mild conditions; Green chemistry.