Hydrochloric Acid → 1-benzyl-4-bromo-1H-pyrazole

A 100 mL round bottom flask was charged with 4-bromopyrazole (4.41 g, 30 mmol), tetrabutylammonium bromide (484 mg, 1.5 mmol) and potassium hydroxide pellets (3.37 g, 60 mmol). After the mixture was sonicated for 15 min, benzyl chloride (5.2 mL, 45 mmol) was added dropwise and the resulting mixture was stirred overnight. Ethyl ether (20 mL), water (20 mL), and diluted hydrochloric acid (1 mL, 10%) were added under stirring. The organic layer was washed with water (2×20 mL) and dried over MgSO4. The solvent was removed under reduced pressure and the product was purified by flash chromatography on silica gel (hexane/ethyl acetate 10:1) to provide the desired product as a white solid (6.74 g, 95% yield). Mp 51-52° C. (lit. 44-45° C., See Jones, R. G. J. Am. Chem. Soc. 1949, 71, 3994). 1H NMR (400 MHz, CDCl3): δ 7.53 (s, 1H), 7.42-7.33 (m, 4H), 7.28-7.22 (m, 2H), 5.29 (s, 2H); 13C NMR (100 MHz, CDCl3): δ 140.4, 136.2, 129.8, 129.4, 128.8, 128.3, 93.9, 57.1.

1. customAfter the mixture was sonicated for 15 min
2. stirringunder stirring
3. washThe organic layer was washed with water (2×20 mL)
4. dry with materialdried over MgSO4
5. customThe solvent was removed under reduced pressure
6. customthe product was purified by flash chromatography on silica gel (hexane/ethyl acetate 10:1)

ORD record

ord-9dd5a1ca0cc94de0b728260cbd28cd29

Source dataset

uspto-grants-2005_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06888032B2