4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole → (S)-1-((2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

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Reaction Steps

A solution of 4-(4,4,5,5-Tetramethyl[1,3,2]dioxaborolan-2-yl)-1H-pyrazole (9.24 g, 47.6 mmol), (R)-(−)-(2,2-Dimethyl-1,3-dioxolan-4-yl)methyl p-toluenesulfonate (15.00 g, 52.38 mmol) and CsHCO3 (23.3 g, 71.4 mmol) in anhydrous DMF (236 mL) was heated to 100° C. for 16 h. The reaction mixture was allowed to cool to rt and partitioned between EtOAc and H2O and separated. The aqueous was re-extracted with EtOAc (3×) and the combined organic fractions were washed with H2O (2×) and brine (2×), dried over Na2SO4, filtered and concentrated in vacuo resulting in the title compound as an orange oil. It was used in the next step without further purification. 1H NMR (400 MHz, CDCl3): δ=1.31 (s, 12H), 1.33 (s, 3H), 1.39 (s, 3H), 3.78 (dd, J=8.8, 5.9 Hz, 1H), 4.07 (dd, J=8.8, 6.2 Hz, 1H), 4.23-4.35 (m, 2H), 4.47 (quint, J=5.8 Hz, 1H), 7.78 (s, 1H), 7.81 (s, 1H).

Provenance & Evidence