Lithium hydroxide, monohydrate → 5-bromo-1-methyl-1H-pyrazole-4-carboxylic acid

A suspension of ethyl 5-bromo-1-methyl-1H-pyrazole-4-carboxylate (8.00 g, 34.3 mmol) in tetrahydrofuran (60 mL), water (20 mL) and ethanol (20 mL) was treated with lithium hydroxide monohydrate (3.17 g, 75.5 mmol) and stirred for 4 hours at room temperature. Removal of solvents under reduced pressure provided a white solid residue, which was diluted with water (50 mL), washed with diethyl ether (50 mL) and adjusted to pH 2.5 with aqueous 6 N hydrochloric acid. The thick suspension was extracted with 2-methyltetrahydrofuran (2×125 mL), and the combined organic layers were dried over magnesium sulfate, filtered and concentrated in vacuo to provide the product as an off-white solid. Yield: 6.49 g, 31.7 mmol, 92%. LCMS m/z 205.2 (M+1). 1H NMR (500 MHz, DMSO-d6) δ 3.86 (s, 3H), 7.91 (s, 1H), 12.64 (br s, 1H).

1. customRemoval of solvents under reduced pressure
2. customprovided a white solid residue, which
3. washwashed with diethyl ether (50 mL)
4. extractionThe thick suspension was extracted with 2-methyltetrahydrofuran (2×125 mL)
5. dry with materialthe combined organic layers were dried over magnesium sulfate
6. filtrationfiltered
7. concentrationconcentrated in vacuo

ORD record

ord-a155244e75fd4767bedb9a89292fe6c3

Source dataset

uspto-grants-2015_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09200000B2