1,4-Dichloro-2-butyne → 1-(4-chloro-but-2-ynyl)-3-nitro-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

3-Nitro-1H-pyrazole (prepared in example 3, 1.30 g, 11.50 mmol) was dissolved in N,N-dimethylformamide (20 mL) and chilled to 0° C. A 60% dispersion of sodium hydride in mineral oil (552 mg, 13.80 mmol) was added portion wise, the ice bath was removed and the reaction continued to stir for 20 min. The 1,4-dichloro-but-2-yne (2.83 g, 23.00 mmol) was dissolved in N,N-dimethylformamide (5 mL) and chilled to 0° C. The 3-nitro-1H-pyrazole solution was added dropwise to the 1,4-dichloro-but-2-yne solution while stirring at 0° C. The ice bath was removed and the reaction continued to stir for 20 min. The solution was diluted with ethyl acetate (400 mL), washed with water (2×200 mL), saturated aqueous brine solution (2×100 mL), dried over magnesium sulfate and concentrated in vacuo to give a yellow oil. Purification by flash column chromatography (Merck silica gel 60, 40-63 μm; 40% ethyl acetate/hexanes) afforded 1-(4-chloro-but-2-ynyl)-3-nitro-1H-pyrazole (682 mg, 30%) as a yellow oil which eventually solidified: H1-NMR (400 MHz, CDCl3) δ 4.18 (2H, t, J=2.0 Hz), 5.08 (2H, t, J=2.0 Hz), 6.92 (1H, d, J=2.4 Hz), 7.70 (2H, d, J=2.4 Hz).

Provenance & Evidence