Abstract: Eight 1,3-dimethyl-2-alkyl ethenyl substituted benzimidazolium salts which were used as the models of N⁵, N¹⁰-C⁺R-tetrahydrofolate(THF) coenzymes at formic acid oxidation level were synthesized by the reaction of o-phenylenediamine with acetic acid giving 2-methyl benzimidazole, and the consecutive reaction with methyl iodide and aldehydes. Their molecular structures were characterized by elemental analysis, ¹HNMR, IR, MS and UV-Vis spectra. These model compounds can react with nucleophilic reagents(Grignard reagents) to give alkyl ethenyl substituted one carbon unit transfer products α,β-unsaturated ketones. A convenient biomimetic method for synthesis of α,β-unsaturated ketones was provided.

Key words: Tetrahydrofolate, Coenzyme model, Benzimidazolium salt, α,β-Unsaturated ketones