Cesium carbonate → 1-[2-(oxan-2-yloxy)ethyl]-4-(tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

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Reaction Steps

To a solution of 4-pyrazole boronic acid pinacol ester (2.0 g, 10.3 mmol) in anhydrous DMF (20 mL) was added cesium carbonate (4.03 g, 12.4 mmol) and the mixture stirred at RT for 10 minutes. 2-(2-Bromoethoxy)tetrahydro-2H-pyran (1.87 mL, 12.4 mmol) was added in two portions and the mixture was heated to 70° C. After heating for 18 hours the mixture was allowed to cool to RT and partitioned between water (100 mL) and EtOAc (100 mL). The aqueous layer was washed with EtOAc (3×20 mL) and the combined organic layers washed with water (3×100 mL) followed by brine, dried (Na2SO4) and concentrated in vacuo. The resultant residue was purified by flash chromatography (SiO2, gradient 0-100% EtOAc in cyclohexane) to afford the title compound (2.15 g, 65%). LCMS: RT=3.97 min, [M+Na]+=345

Provenance & Evidence