1-(2-Propen-1-yl)-4-(4,4,5,5-tetraMethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole synthesis

Yield: 94%

Reaction Conditions:

with sodium hexamethyldisilazane in tetrahydrofuran at 70;

Steps:

36
INTERMEDIATE 36; l-Allyl-4-(4,4.5.5-tetramethyl-ri,3.21dioxaborolan-2-vn-lH^'-pyrazole; A mixture of 4-pyrazoleboronic acid pinacol ester (3.0g, 15.6 mmol), allyl bromide (6.9 g, 77 mmol) and sodium Z?(trimethylsilyl)amide (20.5 mL of a 1.5N solution in THF, 30.7 mmol) in THF (20 mL) was heated to 7O⁰C overnight. After cooling to r.t. the reaction was quenched with water (15 mL) and extracted with EtOAc (2 x 30 mL). The combined organic fractions were washed with brine (50 mL), dried (MgSO₄) and concentrated in vacuo to give the title compound (3.4 g, 94%) as a yellow oil. δ_H (CDCl₃) 1.20 (12H, s), 4.61-4.67 (2H, m), 5.06-5.24 (2H, m), 5.79-6.01 (IH, m), 7.60 (IH, s), 7.69 (IH, s).

References:

UCB PHARMA S.A. WO2008/44022, 2008, A1 Location in patent:Page/Page column 36