Synthesis
Under nitrogen protection, 1,3-dimethoxybenzene (69.1 mg, 0.5 mmol), pinacol ester of bisboronic acid (126.9 mg, 0.5 mmol), methoxy-1,5-cyclooctadienyl iridium dimer (3.4 mg, 0.005 mmol, 1 mol%), and borane pyridine ligand (4.0 mg, 0.01 mmol, 2 mol%), followed by the addition of cyclopentyl methyl ether (1 mL to give a 1,3-dimethoxybenzene concentration of 0.5 mol/L). The reaction mixture was stirred at 100°C for 16 hours. After completion of the reaction, the solvent cyclopentyl methyl ether was removed by rotary evaporation (20-40°C). The crude product was purified by column chromatography (using 200-300 mesh silica gel with a silica gel to sample mass ratio of 50-100:1 and an eluent that was a mixture of petroleum ether and ethyl acetate at a volume ratio of 20-50:1) to give 3,5-dimethoxyphenylboronic acid pinacol ester as a colorless solid (125 mg, 99% yield).
References
[1] Patent: CN104725409, 2016, B. Location in patent: Paragraph 0036; 0037; 0040
[2] Journal of the American Chemical Society, 2015, vol. 137, # 25, p. 8058 - 8061
[3] Research on Chemical Intermediates, 2013, vol. 39, # 4, p. 1917 - 1926
[4] Journal of the American Chemical Society, 2015, vol. 137, # 15, p. 5193 - 5198
[5] Chemistry - A European Journal, 2017, vol. 23, # 26, p. 6282 - 6285
