The general procedure for the synthesis of 1-(ethoxycarbonylmethyl)-1H-pyrazole-4-boronic acid pinacol ester from ethyl 4-bromo-1H-pyrazole-1-acetate and bis-boronic acid pinacol ester was carried out as follows: firstly, 4,4,5,5-tetramethyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,3,2-dioxaboro Heterocyclopentane (436 mg, 1.72 mmol) was dissolved in DMF (10 mL). Subsequently, KOAc (420 mg, 4.29 mmol) and Pd(dppf)Cl2-CH2Cl2 (35 mg, 0.043 mmol) were added sequentially. The reaction mixture was heated to 80 °C and a solution of ethyl 4-bromo-1H-pyrazole-1-acetate (333 mg, 1.43 mmol) in DMF (10 mL) was added dropwise at this temperature. The reaction mixture was stirred at 80 °C overnight and then evaporated to dryness. Finally, the residue was purified by silica gel column chromatography (eluent: ethyl acetate/petroleum ether = 1:10) to afford the target product 1-(ethoxycarbonylmethyl)-1H-pyrazole-4-boronic acid pinacol ester (76 mg, 19% yield).
