Synthesis of the perdeuterated cellulose solvents N-methylmorpholine N-oxide (NMMO-d11 and NMMO-15N-d11), N,N-dimethylacetamide (DMAc-d9 and DMAc-15N-d9), 1-ethyl-3-methylimidazolium acetate (EMIM-OAc-d14) and 1-butyl-3-methylimidazolium acetate (BMIM-OAc-d18)

The syntheses of several perdeuterated substances—some of them isotopically labeled (15N) in addition—are described, which act as direct solvents of cellulose either on their own, such as N-methylmorpholine N-oxide (NMMO), 1-butyl-3-methylimidazolium acetate (BMIM-OAc), or 1-ethyl-3-methylimidazolium acetate (EMIM-OAc), or in combination with auxiliaries, such as N,N-dimethylacetamide (DMAc—for the cellulose solvent DMAc/LiCl). NMMO-d11 (9) was obtained in an eight-step approach from non-labeled diglycolic acid (1) via diethylene glycol-d8 (4) and its bis-tosylate (5), which underwent ring closure with benzylamine to N-benzylmorpholine-d8 (6). Debenzylation, methylation and oxidation completed the synthetic sequence, which was also able to provide the 15N-labeled product (9a) by usage of 15N-benzylamine. DMAc-d9 (14) was obtained from deuterated acetic acid (10) and dimethylamine-d6–carbon dioxide complex (13) in a solvent-free gas-solid reaction with acidic alumina as the catalyst. Employing the CO2-complex of 15N-dimethylamine-d6 afforded the 15N-labeled product 15N-DMAc-d9 (14a) in a similar way. The two ionic liquids EMIM-OAc (21) and BMIM-OAc (22) 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-d6. Addition of acetic acid-d4 caused traceless degradation of the methylcarbonate anions and exchange for acetate. In all syntheses, the reaction steps were optimized with non-labeled compounds towards high yields and high reproducibility before entering the “hot runs” with deuterated and otherwise isotopically labeled material.