Sulfuric Acid → 2-Chloro-4-hydroxybenzoic acid

Temperature

0 °C

4-Amino-2-chloro-benzoic acid methyl ester from Example E41b.1 (5.45 g, 29.4 mmol) was treated with a 35% solution of sulphuric acid (120 ml) and the mixture was stirred and heated until dissolution then cooled to 0° C. Sodium nitrite (4.30 g, 62.5 mmol) in water (25 ml) was added dropwise and the mixture was stirred for 15 min at 0° C. Urea was added to destroy the excess nitrite. Cop-per nitrate (200 mg, 0.83 mmol) was added and heated to 90° C. The reaction mixture was cooled to room temperature, extracted into ethyl acetate×3, dried and concentrated in vacuo. The residue was purified by flash chromatography on silica gel (eluant; 30% EtOAc:70% hexane to 50% EtOAc:49% hexane:1% AcOH) to yield the title compound (3.7 g, 73%).

1. temperatureheated until dissolution
2. stirringthe mixture was stirred for 15 min at 0° C
3. customto destroy the excess nitrite
4. temperatureheated to 90° C
5. temperatureThe reaction mixture was cooled to room temperature
6. extractionextracted into ethyl acetate×3
7. customdried
8. concentrationconcentrated in vacuo
9. customThe residue was purified by flash chromatography on silica gel (eluant; 30% EtOAc:70% hexane to 50% EtOAc:49% hexane:1% AcOH)

ORD record

ord-8319e490595440f4b3881ae5167716f8

Source dataset

uspto-grants-2012_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08202858B2