Borane-Mediated Reduction of Polymeric NHGs

The centrifuged polymeric NHG’s (160 mg) and 319 mg boric acid (5.16 mmol) was poured into a glass pressure tube. A total of 607 µL of trimethyl borate (5.16 mmol) was added followed by the addition of 17 mL 1 M borane-THF complex (17 mmol). After the cessation of hydrogen evolution, the tubes were sealed and kept in an oil bath at 65 °C for 72 h. The NHG’s were then centrifuged and washed with MeOH (10 mL × 2). The obtained precipitate was mixed with methanol (8 mL) and piperidine (2 mL), transferred to a reactor, and heated to 65°C for 20 h under pressure to destroy the borane complexes. Following the decantation of the piperidine-borane solution, water was added, and the suspension was centrifuged and washed with distilled water (10 mL × 3). The reduced NHGs were dialyzed against 25 L DDW for 2 days. The water was changed twice per day.