894807-98-8

General procedure: 1-([2-(trimethylsilyl)ethoxy]methyl)-1H-pyrazole-4-boronic acid pinacol ester was synthesized from 4-pyrazoleboronic acid pinacol ester and 2-(trimethylsilyl)ethoxymethyl chloride. To a solution of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (8.2 g, 41 mmol) in N-methylpyrrolidone (NMP, 60 mL) was added sequentially potassium carbonate (K2CO3, 12 g, 82 mmol) and 2-(trimethylsilyl)ethoxymethyl chloride (7.8 mL, 43 mmol). The reaction mixture was stirred at room temperature for 16 h under the protection of nitrogen (N2). After completion of the reaction, the mixture was diluted and filtered and the filtrate was diluted with ethyl acetate (EtOAc, 300 mL). The resulting solution was washed sequentially with saturated sodium bicarbonate (NaHCO3) aqueous solution (3×200 mL), water (4×200 mL) and brine (1×200 mL), dried over anhydrous sodium sulfate (Na2SO4), filtered, concentrated and dried in vacuum to afford the intermediate 1-([2-(trimethylsilyl)ethoxy]methyl)-1H-pyrazole-4-boronic acid pinacol ester ( 11.4 g, yield 86%) as a light yellow oil.

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