Reactivity of 1,3-dimethylimidazolium-2-carboxylate with dimethylcarbonate at high temperature: Unexpected 2-ethyl-functionalisation of the imidazolium moiety and employment of the NHC-CO2/dimethylcarbonate system in a base promoted reaction

•Reactivity of 1,3-dimethylimidazolium-2-carboxylate with dimethylcarbonate•Unexpected 2-ethyl-functionalization of the imidazolium moiety•Synthesis and characterization of 2-ethyl-1,3-dimethylimidazolium methyl carbonate•Synthesis and characterization of 2-ethyl-1,3-dimethylimidazolium-4-carboxylate•Synthesis of 1,7-heptanedioic acid dimethyl ester

The reaction of 1,3-dimethylimidazolium-2-carboxylate and dimethylcarbonate (DMC) at high temperature yielded the new compounds 2-ethyl-1,3-dimethylimidazolium methyl carbonate salt and 2-ethyl-1,3-dimethylimidazolium-4-carboxylate zwitterion which were obtained as a mixture in approximately 4:1 molar ratio. The compounds were also isolated in pure form through alternative synthetic procedures and characterized by ESI-HRMS, 1H, 13C NMR and FTIR spectroscopy. The 1,3-dimethylimidazolium-2-carboxylate/dimethylcarbonate system was employed in the synthesis of 1,7-heptanedioic acid dimethyl ester from cyclohexanone and DMC. The target compound was obtained in 49% yield and 66% selectivity.

Graphical abstractReactivity of 1,3-dimethylimidazolium-2-carboxylate with dimethylcarbonate at high temperature: unexpected 2-ethyl-functionalisation of the imidazolium moiety and employment of the NHC-CO2/dimethylcarbonate system in a base promoted reaction.Figure optionsDownload full-size imageDownload as PowerPoint slide