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

Temperature

0 °C

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).

1. customthe ice bath was removed
2. temperaturechilled to 0° C
3. stirringwhile stirring at 0° C
4. customThe ice bath was removed
5. stirringto stir for 20 min
6. additionThe solution was diluted with ethyl acetate (400 mL)
7. washwashed with water (2×200 mL), saturated aqueous brine solution (2×100 mL)
8. dry with materialdried over magnesium sulfate
9. concentrationconcentrated in vacuo
10. customto give a yellow oil
11. customPurification by flash column chromatography (Merck silica gel 60, 40-63 μm; 40% ethyl acetate/hexanes)

ORD record

ord-3f361c790ec640d4aa58835ac7f5cfc8

Source dataset

uspto-grants-2011_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07935699B2