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

Participants

Reaction Steps

A solution of 4-(4,4,5,5-tetramethyl[1,3,2]dioxaborolan-2-yl)-1H-pyrazole (0.375 g, 1.93 mmol), (R)-3-methanesulfonyloxypyrrolidine-1-carboxylic acid tert-butyl ester (0.513 g, 1.93 mmol), and Cs2CO3 (0.943 g, 2.90 mmol) in anhydrous DMF (5.1 mL) was heated to 100° C. for 6 h. The reaction mixture was partitioned between EtOAc and H2O and separated. The aqueous layer 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 brown oil. This material crude was purified by chromatography on silica gel [eluting with 12% EtOAc in CHCl3] resulting in the title compound as a viscous oil. 1H NMR (400 MHz, CDCl3): δ=1.32 (s, 12H), 1.47 (s, 9H), 2.36 (q, J=7.0 Hz, 2H), 3.46-3.79 (m, 3H), 3.81-3.92 (m, 1H), 4.90 (quint, J=6.1 Hz, 1H), 7.73 (s, 1H), 7.81 (s, 1H).

Provenance & Evidence