Synthesis
General procedure for the synthesis of 3,5-dimethoxycarbonylphenylboronic acid pinacol ester from dimethyl 5-bromoisophthalate and pinacol ester of bisboronic acid: dimethyl 5-bromo-1,3-benzenedicarboxylate (5.4 g, 19.8 mmol) and pinacol ester of boronic acid (6.0 g, 29.4 mmol) were added into a 250 mL three-necked flask and anhydrous 1,4-dioxane (50 mL) was added As a solvent, Pd(dppf)2Cl2 (0.2 g, 0.27 mmol) was added under nitrogen protection. The reaction mixture was heated to 100 °C and kept for 12 hours. Upon completion of the reaction, it was cooled to room temperature and the excess 1,4-dioxane was removed by distillation. Water (20 mL) was added and extracted with ethyl acetate (30 mL x 3), the organic phases were combined and dried with anhydrous Na2SO4. After filtration, the filtrate was evaporated to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate=94/6) to afford 3,5-dimethoxycarbonylphenylboronic acid pinacol ester (4.59 g, 72% yield) in white powder form.
References
[1] Chemical Communications, 2015, vol. 51, # 40, p. 8508 - 8511
[2] Journal of the American Chemical Society, 2013, vol. 135, # 32, p. 11887 - 11894
[3] Patent: CN105237337, 2016, A. Location in patent: Paragraph 0021
[4] Chemical Communications, 2013, vol. 49, # 20, p. 2043 - 2045
[5] Inorganic Chemistry, 2015, vol. 54, # 9, p. 4377 - 4381
