Simple, facile and complete green syntheses of -alkyl-2-styrylbenzimidazoles using glycerol and PEG-600 as green solvents

Simple and green methodologies for the syntheses of 2-styrylbenzimidazoles 3(a-c) and its N-alkyl derivatives 7(a-i) have been developed. o-Phenylenediamine 1 was condensed with cinnamic acids 2(a-c) resulting in 2-styrylbenzimidazoles 3(a-c) using glycerol as a green and efficient solvent. 3 were also prepared alternatively by the condensation of 2-methylbenzimidazole 4 with benzaldehydes 5(a-c) using glycerol as solvent. 2-Styrylbenzimidazoles 3(a-c) and 2-methylbenzimidazole 4 were alkylated independently to obtain N-alkyl-2-styrylbenzimidazole 7(a-i) and N-alkyl-2-methylbenzimidazole 6(a-c) respectively using DMS/DES/PhCH2Cl applying green methods such as simple physical grinding of reactants in solid phase, treating reactants in PEG-600 as a solvent in solution phase and using Microwave irradiation of reactants respectively. 7(a-i) could also be prepared, alternatively, by heating 6(a-c) with 5(a-c) in glycerol at 1800C for 3-4 hrs

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