Acetic Anhydride → 4-chloro-5-methyl-1H-indazole

the known 3-chloro-2,4-dimethylaniline (14.9 g, 96 mmol) in 250 mL of anhydrous benzene was treated with potassium acetate (9.4 g, 96 mmol) and acetic anhydride (29.4 g, 288 mmol). This mixture was slowly heated to reflux while a precipitate formed. Subsequently, isoamyl nitrite (17 g, 144 mmol) was added rapidly to the refluxing suspension and heating was continued for 18 hours. The cooled suspension was filtered and the solid rinsed with benzene. The combined filtrates were evaporated and the solid residue was dissolved in 200 mL of ethanol containing 1 mL of conc. hydrochloric acid. This mixture was heated under reflux for 5 hours and the solvent was removed in vacuo. The solid residue was washed with 5% sodium bicarbonate and dissolved in ethyl acetate, dried over sodium sulfate and evaporated to give 9.3 g of intermediate solid.

1. temperatureThis mixture was slowly heated
2. temperatureto reflux while a precipitate
3. customformed
4. temperatureheating
5. filtrationThe cooled suspension was filtered
6. washthe solid rinsed with benzene
7. customThe combined filtrates were evaporated
8. dissolutionthe solid residue was dissolved in 200 mL of ethanol containing 1 mL of conc. hydrochloric acid
9. temperatureThis mixture was heated
10. temperatureunder reflux for 5 hours
11. customthe solvent was removed in vacuo
12. washThe solid residue was washed with 5% sodium bicarbonate
13. dissolutiondissolved in ethyl acetate
14. dry with materialdried over sodium sulfate
15. customevaporated

ORD record

ord-8a8c8b17d40f49568dfd52a38af3aefa

Source dataset

uspto-grants-1999_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05928998