Sulfuric Acid → 3-Hydroxy-5-nitrobenzoic acid

To a solution of 3-amino-5-nitro-benzoic acid methyl ester (Example 313, 1.96 g, 10 mmol) in 23 mL of H2O and 5 mL of con. H2SO4 at 0° C., was added a solution of NaNO2 (Aldrich, 900 mg, 13 mmol) in 9 mL of H2O. After 50 min stirring, the resulting diazonium salt was added to a solution of 17 mL of H2O and 17 mL of con. H2SO4 at 90° C. After stirred at 90° C. for 90 min, the mixture was cooled to room temperature and brought to pH 3 with con. NH4OH. The mixture was extracted 3× with EtOAc (100 mL). The organic layers were washed twice with a brine solution (100 mL), dried over Na2SO4 and concentrated. The residue was purified by chromatography (5%-10% MeOH/CH2Cl2) to give 705 mg (39%) of product. 1H NMR (400 MHz, DMSO-d6) δ 13.64 (br s, 1H), 10.84 (s, 1H), 8.08 (t, J=1.8 Hz, 1H), 7.75 (t, J=2.2 Hz, 1H), 7.70 (dd, J=2.2, 1.3 Hz, 1H), 6.16 (s, 2H), 3.87 (s, 3H). MS (EI): m/z 184 (M+H).

1. customat 90° C
2. stirringAfter stirred at 90° C. for 90 min
3. extractionThe mixture was extracted 3× with EtOAc (100 mL)
4. washThe organic layers were washed twice with a brine solution (100 mL)
5. dry with materialdried over Na2SO4
6. concentrationconcentrated
7. customThe residue was purified by chromatography (5%-10% MeOH/CH2Cl2)

ORD record

ord-55e9eb481ec846fa8fdb50b20d8207e6

Source dataset

uspto-grants-2009_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07601841B2