[CH3:1][C:2]1([CH3:14])[C:6]([CH3:8])([CH3:7])[O:5][B:4]([C:9]2[CH:10]=[N:11][NH:12][CH:13]=2)[O:3]1.[CH3:15][O:16][C:17](=[O:22])[C:18](Br)([CH3:20])[CH3:19].C([O-])([O-])=O.[Cs+].[Cs+]>CN(C=O)C>[CH3:15][O:16][C:17](=[O:22])[C:18]([CH3:20])([N:12]1[CH:13]=[C:9]([B:4]2[O:5][C:6]([CH3:7])([CH3:8])[C:2]([CH3:14])([CH3:1])[O:3]2)[CH:10]=[N:11]1)[CH3:19]To a solution of 4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-pyrazole (5 g, 25.77 mmol) and 2-bromo-2-methyl-propionic acid methyl ester (12.6 g, 27.06 mmol) in DMF (85 mL), was added Cs2CO3 (12.6 g, 38.65 mmol). The reaction mixture was heated to 90° C. in an oil bath overnight. The reaction solution was cooled to room temperature, and partitioned between water and ethyl acetate. The combined ethyl acetate solution was washed with water five times, dried over Na2SO4, and concentrated to give the product 2-methyl-2-[4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-pyrazol-1-yl]propionic acid methyl ester (4.776 g, 63% yield).
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