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

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, H-1, C-13 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. (C) 2013 Elsevier B.V. All rights reserved.