Cesium carbonate → (R)-(1-(1-(tert-Butoxycarbonyl)pyrrolidin-3-yl)-1H-pyrazol-4-yl)boronic acid pinacol ester

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Reaction Steps

A solution of 4-(4,4,5,5-tetramethyl[1,3,2]dioxaborolan-2-yl)-1H-pyrazole (0.856 g, 4.41 mmol), (S)-3-methanesulfonyloxy-pyrrolidine-1-carboxylic acid tert-butyl ester (1.17 g, 4.41 mmol) and Cs2CO3 (2.16 g, 6.61 mmol) in anhydrous DMF (11.7 mL) was heated to 100° C. for 16 h. The reaction mixture was allowed to cool to rt and was partitioned between EtOAc and H2O and separated. The aqueous was re-extracted with EtOAc (3×) and the combined organic fractions were washed with H2O (3×), brine (2×), dried over Na2SO4, filtered and concentrated in vacuo resulting in a crude brown oil. The reaction mixture was purified by chromatography on silica gel [eluting with 12% EtOAc in CHCl3]resulting in 538 mg, 33% yield of the title compound as a light yellow oil. 1H NMR (400 MHz, CDCl3) δ 1.31 (s, 12H), 1.46 (s, 9H), 2.36 (q, J=7.0 Hz, 2H), 3.46-3.78 (m, 3H), 3.80-3.91 (m, 1H), 4.89 (quint, J=6.1 Hz, 1H), 7.73 (s, 1H), 7.80 (s, 1H).

Provenance & Evidence