Sulfuric Acid → ethyl 1-(3,5-dichloropyridin-2-yl)-3-hydroxy-1H-pyrazole-5-carboxylate

To a 100 mL flask, ethyl 2-(3,5-dichloropyridin-2-yl)-5-oxopyrazolidine-3-carboxylate (4.00 g, 13.15 mmol), acetonitrile (50 mL) and 98% sulfuric acid (2.63 g, 26 mmol) were added. The mixture was stirred for 10 minutes, and then potassium persulfate (5.69 g, 21.04 mmol) was added. The reaction mixture was heated to reflux for 5 hours. The warm (50-65° C.) reaction mixture was filtered, a cake is obtained after filtration. The cake was washed with acetonitrile (10 mL). The filtrate was concentrated to about 10 mL on rotary evaporator. Then water (50 mL) was added. The solid product was isolated by filtration, washed with 25% aqueous solution of acetonitrile (3×15 mL) and dried to give the product (3.0 g) as an orange solid in 76% yield. Melting point: 164-167° C. 1H NMR (300 MHz, CDCl3): 8.445 (d, 1H), 7.912 (d, 1H), 6.546 (s, 1H), 4.262 (q, 2H), 1.236 (t, 3H).

1. temperatureThe reaction mixture was heated
2. temperatureto reflux for 5 hours
3. temperatureThe warm
4. custom(50-65° C.) reaction mixture
5. filtrationwas filtered
6. customa cake is obtained
7. filtrationafter filtration
8. washThe cake was washed with acetonitrile (10 mL)
9. concentrationThe filtrate was concentrated to about 10 mL on rotary evaporator
10. additionThen water (50 mL) was added
11. customThe solid product was isolated by filtration
12. washwashed with 25% aqueous solution of acetonitrile (3×15 mL)
13. customdried

ORD record

ord-47f3e5174d2f49699c38a9f0cb92de23

Source dataset

uspto-grants-2013_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08492409B2