Water → 4-Bromo-3-(difluoromethyl)-1-methyl-1H-pyrazole

At from 3 to 5° C., a solution of N-bromosuccinimide (NBS, 54 g, 0.3 mol) in dimethyl-formamide (DMF, 100 ml) was added dropwise to a solution of 3-difluoromethyl-N-methylpyrazole (49.3 g, 0.3 mol; 81.4% pure according to GC analysis) comprising, as minor component, 5.2% of 5-difluoromethyl-N-methylpyrazole, based on the total amount of the isomer mixture, in DMF (100 ml). The reaction mixture was then warmed to room temperature and stirred for a further 12 h. With stirring, the reaction mixture was then poured into water (1000 ml) and extracted twice with methyl tert-butyl ether (MTBE, 300 ml). The organic phases were combined, washed with a saturated aqueous solution of NaCl, dried over magnesium sulfate, filtered and then freed from the solvent under reduced pressure. 4-Bromo-3-difluoromethyl-N-methylpyrazole was obtained as an oil (76.6 g; purity: 74.2% according to GC analysis) comprising 4.5% of unreacted 5-difluoromethyl-N-methylpyrazole. This corresponds to a yield of 89%.

1. stirringWith stirring
2. extractionextracted twice with methyl tert-butyl ether (MTBE, 300 ml)
3. washwashed with a saturated aqueous solution of NaCl
4. dry with materialdried over magnesium sulfate
5. filtrationfiltered

ORD record

ord-d2e77615b8c247d3a67974c3b5fbc65d

Source dataset

uspto-grants-2012_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08153820B2