Reaction #8596

Reaction equation

Boron trifluoride

7-chloro-2-(4-methoxyphenyl)pyrazolo[1,5-α]pyridine

acetic anhydride

→

1-[7-(chloro)-2-(4-methoxyphenyl)pyrazolo[1,5-α]pyridin-3-yl]ethanone

Yield 65.2%

Solvents

toluene

Conditions

Workup

1. 1
   Temperaturethe resulting solution was heated
2. 2
   Temperatureat reflux for 4 hours
3. 3
   Otherquenched by the dropwise addition of saturated aqueous sodium bicarbonate
4. 4
   ExtractionThe reaction was extracted with ethyl acetate
5. 5
   Washthe ethyl acetate phase washed with brine
6. 6
   Dryingdried (magnesium sulfate)
7. 7
   Filtrationfiltered
8. 8
   Concentrationconcentrated
9. 9
   OtherThe residue was purified by recrystallization from ethyl acetate-hexanes

Procedure

To a solution of 7-chloro-2-(4-methoxyphenyl)pyrazolo[1,5-α]pyridine (18.7 g, 72.4 mmol) in toluene (300 mL) at room temperature was added acetic anhydride (8.2 mL, 86.9 mmol). Boron trifluoride diethyletherate (10.1 mL, 79.6 mmol) was then added dropwise and the resulting solution was heated at reflux for 4 hours. The reaction mixture was cooled to room temperature and quenched by the dropwise addition of saturated aqueous sodium bicarbonate. The reaction was extracted with ethyl acetate, and the ethyl acetate phase washed with brine, dried (magnesium sulfate), filtered and concentrated. The residue was purified by recrystallization from ethyl acetate-hexanes to give 1-[7-(chloro)-2-(4-methoxyphenyl)pyrazolo[1,5-α]pyridin-3-yl]ethanone (14.2 g, 65%) as reddish needles.1H NMR (CDCl3): δ 8.37 (dd, 1H), 7.49 (dd, 2H), 7.39 (dd, 1H), 7.10 (dd, 1H), 6.98 (dd, 2H), 3.84 (s, 3H), 2.13 (s, 3H); MS m/z 301 (M+1).

Source