3-Methyl-4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-pyrazole

1021919-24-3

73183-34-3

936250-20-3

The general procedure for the synthesis of 3-methylpyrazole-4-boronic acid pinacol ester from 4-bromo-3-methyl-1H-pyrazole-1-carboxylic acid tert-butyl ester and pinacol ester of bis-boronic acid is as follows: 1. tert-butyl 4-bromo-3-methyl-1H-pyrazole-1-carboxylate (0.48 g, 1.84 mmol), bis(pinacolato)diboron (0.535 g, 2.1 mmol), dichloro[1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloromethane adduct (0.156 g, 0.19 mmol), and potassium acetate ( 0.56 g, 5.7 mmol) were added sequentially to a sealed tube. 2. Add DMSO (5 mL) as a solvent to ensure that all solids are fully dissolved. 3. Flush the reaction system with nitrogen to remove oxygen and subsequently seal the reaction tube. 4. Heat the reaction mixture to 90°C and maintain this temperature for 18 hours. 5. 5. Upon completion of the reaction, the solvent was removed and the crude product was purified by silica gel column chromatography (eluent: 50% ethyl acetate in hexane solution) to afford the target compound, 3-methylpyrazole-4-boronic acid pinacol ester (0.2 g, 50% yield). 6. The structure of the product was confirmed by mass spectrometry (ESI), m/z 209.1 [M + 1]+.