Easy, Simplistic and Green Synthesis of Various Benzimidazole and Benzoxazole Derivatives Using PEG₄₀₀ as a Green Solvent

Abstract

An improved environmentally benign procedure for the synthesis of various benzimidazole and benzoxazole derivatives using green solvent PEG400. We have optimized the reaction condition and it was found that PEG400 was believed to be best as compared to PEG200, PEG600 and PEG800 at 80 to 85 °C. This method provides a novel route for the synthesis of benzimidazole and benzoxazole derivatives. The main attractive features of this process are a mild reaction conditions, easy workup procedure and good to excellent yield. The structures of all the synthesized compounds were confirmed by 1H NMR, IR, MASS and Elemental Analysis.

Green Synthesis of Benzimidazole Derivatives: an Overview on Green Chemistry and Its Applications

“…Green chemistry (GC) involves the use of a set of principles that reduces or removes the use or formation of hazardous substances in the design, manufacture, and application of chemical products [46]. As we design new chemical synthesis, decisions about what hazardous substances are used and what toxic materials should be handled are being made.…”

A Review on the Modern Synthetic Approach of Benzimidazole Candidate

“…This reaction system gives the best yield in PEG‐400 at 80–85 °C. This reaction route is the novel route using PEG and reaction under Glycerol/water method are reported for the synthesized target molecule (Scheme ) …”

“…This reaction route is the novel route using PEG and reaction under Glycerol/water method are reported for the synthesized target molecule (Scheme 38). [84] Kathirvelan et al in 2013 reported one-pot good yield synthesis scheme of MSB (143 a-c) scaffold by the condensation of benzene-1,2-diamine (141) with various aldehyde (142) in the presence of green and economically viable catalyst ammonium chloride at 80-90 °C give moderate to better yield (143 a-c)(Scheme 39). [85] Peng et al reported a method in 2012 for the synthesis of benzimidazole (144 a-b) ring system via intermolecular cyclization of N-(2-iodoaryl) benzamidine (144) in presence of base, at 100 °C potassium carbonate and caesium carbonate used as a base to gives the best yield of product (144 a-b).…”

“…Reaction of benzimidazole in the presence of PEG. [84] Scheme 39. Synthesis of benzimidazole in the presence of ammonium chloride.…”