4-broMo-3-(difluoroMethyl)-1-Methyl-1H-pyrazole

4-broMo-3-(difluoroMethyl)-1-Methyl-1H-pyrazole Property

Boiling point:

235℃

Density 

1.79

Flash point:

96℃

storage temp. 

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

pka

-1.91±0.10(Predicted)

Appearance

Colorless to light yellow Liquid

Hazard and Precautionary Statements (GHS)

Symbol(GHS)

Signal word

Warning

Hazard statements

H302Harmful if swallowed

Precautionary statements

P280Wear protective gloves/protective clothing/eye protection/face protection.

P305+P351+P338IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continuerinsing.

4-broMo-3-(difluoroMethyl)-1-Methyl-1H-pyrazole Chemical Properties,Usage,Production

Synthesis

1.3 Preparation of 4-bromo-3-difluoromethyl-1-methylpyrazole 1.3.a) Bromination reaction: bromine (Br2, 3g) was slowly added dropwise to a solution of 3-difluoromethyl-1-methylpyrazole (2.0g) in dichloromethane (80ml) at 25°C. The reaction mixture was stirred continuously for 22 hours. The reaction mixture was stirred continuously at 25°C for 22 h. After that, 0.1 M aqueous sodium thiosulfate solution (210 ml) was added to quench the reaction. After separation of the organic phase, the solvent was removed by distillation under reduced pressure (40 °C/5 mbar). The crude product (2.4 g, from 2.8 g of crude) was purified by column chromatography (SiO2, ethyl acetate/cyclohexane 1:6) to afford 4-bromo-3-difluoromethyl-1-methylpyrazole (1.4 g). Product characterization data: EI-MS [m/z]: 210, 212 [M]+; 1H-NMR (400MHz, CDCl3): δ= 3.9 (s, 3H), 6.68 (t, 1H), 7.43ppm (s, 1H); 13C-NMR (125MHz, CDCl3): δ= 39.84, 91.47, 110.48 , 132.10, 143.54ppm. 1.3.b) Bromination of N-bromosuccinimide (NBS): a solution of N-bromosuccinimide (NBS, 7.9 g, 0.04 mol) in dimethylformamide (DMF, 20 ml) was slowly added dropwise (slightly exothermic) to a solution of 3-difluoromethyl-1-methylpyrazole (5.0 g, 0.04 mol) in DMF (40 ml) at 3-5°C. The reaction mixture was then warmed to room temperature. The reaction mixture was then warmed to room temperature and stirring was continued for 2 hours. Upon completion of the reaction, the mixture was poured into a mixture of water (200 ml) and aqueous sodium hydroxide solution (5 ml) and extracted four times with methyl tert-butyl ether (MTBE, 100 ml). The combined organic phases were washed with saturated aqueous NaCl, dried over magnesium sulfate and filtered, and the solvent was removed under reduced pressure to give 4-bromo-3-difluoromethyl-1-methylpyrazole (9.5 g; purity: 94.5% (GC analysis); yield: 95.2%).

References

[1] Patent: US2010/174094, 2010, A1. Location in patent: Page/Page column 11-12
[2] Organic Letters, 2018, vol. 20, # 15, p. 4562 - 4565
[3] Patent: EP2008996, 2008, A1. Location in patent: Page/Page column 9; 12-13
[4] Patent: US2010/174094, 2010, A1. Location in patent: Page/Page column 20