Cesium carbonate → (1-(2-bromoethyl)-3-nitro-1H-pyrazol-5-yl)methanol

Participants

Reaction Conditions

Reaction Steps

A 1-L three-necked round-bottomed flask equipped with a mechanical stirrer and thermoregulator was purged with nitrogen and charged with 124a (25.0 g, 175 mmol), DMF (250 mL), and cesium carbonate (70.0 g, 215 mmol) was heated at 104° C. for 5 min. The reaction mixture was then cooled to 0° C. using an ice/acetone bath and dibromoethane (329 g, 1.75 mol) was added portionwise (no exotherm). The reaction was stirred at 0° C. for 1 then at room temperature for 4 h. After this time a solution of KH2PO4 (40 g) in water (400 mL) was added slowly. The reaction mixture was stirred at room temperature for 30 min. Ethyl acetate (450 mL) was added and the aqueous layer was separated and extracted with ethyl acetate (2×100 mL). The combined organic layers were washed with water (200 mL), brine (200 mL), dried over sodium sulfate, and the drying agent was removed by filtration. The filtrate was concentrated under reduced pressure to afford an 86% yield (37.5 g) of crude 124b as an orange oil: 1H NMR (300 MHz, CDCl3) δ 6.85 (s, 1H), 4.82 (d, 2H, J=5.4 Hz), 4.66 (t, 2H, J=6.3 Hz), 3.83 (t, 2H, J=6.3 Hz); MS (ESI+) m/z 249.9 (M+H).

Provenance & Evidence