Bismaleimide

5-hydroxymethyl furfural (HMF, AK Scientific, 98%), Pentaerythritol (Sigma-Aldrich, 99%), p-toluenesulfonic acid (p-TSA) monohydrate (Sigma-Aldrich, ≥98.5%), NaHCO₃ (Sigma-Aldrich, ≥99.7%), Bismaleimide (Sigma-Aldrich, 95%), Ethylene glycol (EG, Sigma-Aldrich, anhydrous, 99.8%), ,4’-methylenebis(phenyl isocyanate) (MDI, Sigma-Aldrich, 98%), Isopropanol (Sigma-Aldrich, for HPLC), 4Acetone (Fisher Scientific, HPLC grade), Tetrahydrofuran (THF, Sigma-Aldrich, 250 ppm BHT inhibitor, ≥99.0%), Dimethyl sulfoxide (DMSO, Sigma-Aldrich, anhydrous, ≥99.9%), 4-methyl-2-pentanone (MIBK, Sigma-Aldrich, HPLC grade), Ethyl acetate (EtOAc, Sigma-Aldrich, for HPLC, ≥99.7%), Acetic acid (Sigma-Aldrich, ≥99.7%), Hydrochloric acid (HCl, 6 N, Fisher Scientific), Sodium acetate (NaOAc, Sigma-Aldrich, >99%), Mill-Q water (MQ water, ~18 MΩ cm), Acetone-d₆ (ACROS organic, 99.8 atom% D, 0.03 % (v/v) TMS), Methanol-d₄ (ACROS organic, 99.8 atom% D, 0.03 % (v/v) TMS), DMSO-d₆ (Sigma-Aldrich, 99.9 atom% D, 0.03 % (v/v) TMS).

The following materials were used in all experiments: 5-(hydroxymethyl) furfural (HMF, AK Scientific, 98%), Acetone (Fisher, HPLC grade), 4,4’-methylenebis(phenyl isocyanate) (MDI, Sigma-Aldrich, 98%), Maleimide (99%, Sigma-Aldrich), BisMaleimide (95%, Sigma-Aldrich), Succinic acid (99%, Sigma-Aldrich), Dibutyltin (IV) oxide (98%, Sigma-Aldrich), Dimethyl sulfoxide (DMSO, Sigma-Aldrich, anhydrous, ≥99.9%), 4-methyl-2-pentanone (MIBK, Sigma-Aldrich, HPLC grade), 2-propanol (IPA, HPLC grade, Sigma-Aldrich),Tetrahydrofuran (THF, Sigma-Aldrich), Gamma alumina (Strem Chemicals), Tetraaminecopper(II) sulfate ([Cu(NH₃)₄]SO₄·_xH₂O, Strem Chemicals), 0.5 M ammonium hydroxide solution (Sigma-Aldrich), 2 M sulfuric acid (Sigma-Aldrich), 5wt% Ru/C catalyst (Sigma-Aldrich), NaOH (FCC specification, Fisher Scientific), HCl (37 wt%, Sigma-Aldrich), Milli-Q water (~18 MΩ cm). Hydrogenation was performed in a 50 mL Parr reactor (Parr Instrument Company).