Triphenylphosphine → 4-bromo-1-(3-methylbut-3-en-2-yl)-1H-pyrazole

Temperature

0 °C

(E)-Di-tert-butyl diazene-1,2-dicarboxylate (940 mg, 4.08 mmol) was added slowly to a stirred solution of 3-methylbut-3-en-2-ol (293 mg, 3.40 mmol), triphenylphosphine (1.07 g, 4.08 mmol), and 4-bromo-1H-pyrazole (500 mg, 3.40 mmol) in THF (10 mL) at 0° C. The reaction was stirred for 10 min at 0° C. and then allowed to warm to RT for 1 hour. The reaction was quenched into water and the product was extracted with ethyl acetate (2×20 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to afford an oil. The oil was dissolved in 20% trifluoroacetic acid in dichloromethane (5 mL) and stirred for 20 minutes. The reaction mixture was concentrated under reduced pressure and the residue was dissolved in ethyl acetate, washed with 10% aqueous sodium bicarbonate, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to afford the crude residue. The crude residue was purified by column chromatography on silica (20-100% ethyl acetate/hexanes) to afford 4-bromo-1-(3-methylbut-3-en-2-yl)-1H-pyrazole. MS ESI calcd. for C8H12BrN2 [M+H]+ 215 and 217. found 215 and 217.

1. temperatureto warm to RT for 1 hour
2. customThe reaction was quenched into water
3. extractionthe product was extracted with ethyl acetate (2×20 mL)
4. dry with materialdried over anhydrous magnesium sulfate
5. filtrationfiltered
6. concentrationconcentrated under reduced pressure
7. customto afford an oil
8. stirringstirred for 20 minutes
9. concentrationThe reaction mixture was concentrated under reduced pressure
10. dissolutionthe residue was dissolved in ethyl acetate
11. washwashed with 10% aqueous sodium bicarbonate
12. dry with materialdried over anhydrous sodium sulfate
13. filtrationfiltered
14. concentrationconcentrated under reduced pressure
15. customto afford the crude residue
16. customThe crude residue was purified by column chromatography on silica (20-100% ethyl acetate/hexanes)

ORD record

ord-c3fc2d36ea984c3f84bf4de0b8111764

Source dataset

uspto-grants-2016_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09242984B2