3-chloro-1H-pyrazole Chemical Properties

Melting point:

40 °C

Boiling point:

250.9±13.0 °C(Predicted)

Density 

1.405±0.06 g/cm3(Predicted)

storage temp. 

under inert gas (nitrogen or Argon) at 2-8°C

form 

powder

pka

11.04±0.10(Predicted)

color 

White

InChI

InChI=1S/C3H3ClN2/c4-3-1-2-5-6-3/h1-2H,(H,5,6)

InChIKey

IJPFBRONCJOTTA-UHFFFAOYSA-N

SMILES

N1C=CC(Cl)=N1

Safety Information

HS Code 

2933992000

3-chloro-1H-pyrazole Usage And Synthesis

Uses

5-Chloro-1h-pyrazole is used in preparation of aminoquinazolines as P2X3 inhibitors.

Synthesis

General procedure for the synthesis of 3-chloro-1H-pyrazole from 3-aminopyrazole: Concentrated hydrochloric acid (20 mL) was slowly added to a solution of acetonitrile (600 mL) containing 1H-pyrazol-3-amine (20.0 g, 241 mmol), followed by the addition of copper(II) chloride (65.0 g, 481 mmol) at 0 °C. The reaction mixture was stirred at 0 °C for 30 min followed by dropwise addition of isoamyl nitrite (56.4 g, 481 mmol). The reaction mixture was continued to be stirred at room temperature for 2 days. After completion of the reaction, the reaction was quenched with 10% aqueous ammonia solution (1 L). The aqueous phase was extracted with ethyl acetate (5 x 500 mL) and the combined organic phases were washed with saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated. The residue was purified by silica gel column chromatography (eluent: hexane/ethyl acetate=20:1) to afford the target product 3-chloro-1H-pyrazole (10.3 g, 42% yield) as a green oil.1H NMR (400 MHz, CDCl3): δ 12.84 (br s, 1H), 7.62 (s, 1H), 6.29 (s, 1H).

References

[1] Patent: WO2018/85247, 2018, A1. Location in patent: Paragraph 00296; 00297

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