Water → 1-(3-Chloropyridin-2-yl)-3-hydroxy-1H-pyrazole-5-carboxylic acid

To a stirred solution of ethyl 1-(3-chloro-2-pyridinyl)-2,3-dihydro-3-oxo-1H-pyrazole-5-carboxylate (i.e. the product of Step B) (1.0 g, 3.7 mmol) in methanol (15 mL) was added water (3 mL). An aqueous solution of sodium hydroxide (50%, 1.0 g, 12.5 mmol) was added dropwise, and the reaction mixture was stirred at room temperature for 3 hours, during which time the reaction mixture turned a clear yellow. Water (20 mL) was added and the reaction mixture was extracted with ethyl ether, which was discarded. The aqueous phase was acidified to pH 2 using concentrated hydrochloric acid and then extracted with ethyl acetate (50 mL). The ethyl acetate extract was washed with water (20 mL) and brine (20 mL), dried over magnesium sulfate and concentrated to give the title compound, isolated as a white solid (0.76 g).

1. extractionthe reaction mixture was extracted with ethyl ether, which
2. extractionextracted with ethyl acetate (50 mL)
3. extractionThe ethyl acetate extract
4. washwas washed with water (20 mL) and brine (20 mL)
5. dry with materialdried over magnesium sulfate
6. concentrationconcentrated

ORD-Eintrag

ord-073fbd7a393747a2b3acb4b5d1c25849

Quelldatensatz

uspto-grants-2010_02

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US07666882B2