Cesium carbonate → 1-(2-Methoxyethyl)-1H-pyrazole-4-boronic acid, pinacol ester

Participants

Reaction Steps

A solution of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (0.8 g, 4.1 mmol), cesium carbonate (2.0 g, 6.2 mmol), and 1-(chloromethoxy)-2-methoxyethane (0.59 mL, 5.2 mmol) in DMF (14 mL) was heated in a microwave at 90° C. for 1 hr. After the initial heating, additional 1-(chloromethoxy)-2-methoxyethane (0.59 mL) and cesium carbonate (2 g) was added. Heating was repeated for an additional 1 hr. The crude reaction mixtures were then diluted with water (250 mL) and extracted with ethyl acetate (3×50 mL). The title compound was purified by silica gel column using DCM/EtOAc/MeOH (8/1.5/0.5) as eluent to give 1-(2-methoxyethyl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (1.6 g) as a light yellow oil. ESI-MS:m/z 283.2 (M+H)+.

Provenance & Evidence