Synthesis of the perdeuterated cellulose solvents 1-ethyl-3-methylimidazolium acetate (EMIM-OAc-d14) and 1-butyl-3-methylimidazolium acetate (BMIM-OAc-d18) and of 2-13C-butyl-3-methylimidazolium acetate

The syntheses of two perdeuterated ionic liquids (ILs), which have found use as solvents for cellulose derivatization and processing in addition, are described: 1-ethyl-3-methylimidazolium acetate (EMIM-OAc-d(14)) and 1-butyl-3-methylimidazolium acetate (BMIM-OAc-d(18)). The targets were obtained from imidazole in three-step sequences starting with butylation and ethylation, respectively. The resulting 1-alkyl imidazoles were purified, and subsequently methylated according to a novel protocol using dimethylcarbonate-d(6). To obtain the 1-alkyl-3-methylimidazolium moiety, methylation of 1-alkylimidazoles proved to be superior to the conventional approach of alkylating 1-methylimidazole. Addition of acetic acid-d(4) caused traceless degradation of the methylcarbonate counter anions, which were neatly exchanged for acetate. The IL 2-C-13-butyl-3-methylimidazolium acetate, in which the isotopically enriched C-2 is a good NMR-indicator of side reactions and solvent-solute interactions, was synthesized according to the same reaction sequence, starting from 2-C-13-1-alkylimidazole which, in turn, was obtained by reaction of glyoxale, alkylamine, ammonia and paraformaldehyde-C-13. Copyright (C) 2009 John Wiley & Sons, Ltd.