2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 5-phenyl-1H-pyrrole-2-carboxylic acid

To a 1L round bottomed flask with a stirring bar and an argon inlet was added 5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylic acid ethyl ester AV-4-1 (4.84 g, 22.28 mmol), dry CH2Cl2 (220 mL) and DDQ (5.06 g, 22.28 mmol). This solution was stirred at ambient temperature 1 h. The solvent was removed in vacuo. Aqueous NaOH (10% w/v, 440 mL) was added and the mixture was heated at reflux 24 h. The cooled, black solution was poured onto crushed ice and the mixture was acidified with conc. HCl. This mixture was extracted with EtOAc (2×). The combined extracts were washed with brine, dried (MgSO4), filtered and concentrated in vacuo. The crude product was chromatographed on silica gel using 2.5% MeOH in EtOAc as eluant to give 5-phenyl-1H-pyrrole-2-carboxylic acid AV-5-1 as an off white solid. 1H NMR (CDCl3) δ 6.59 (1H, dd, j=2.7, 3.9 Hz), 7.13 (1H, dd, j=2.7, 3.9 Hz), 7.34 (1H, m), 7.41 (2H, m), 7.59 (2H, m), 9.40 (1H, br s).

1. customThe solvent was removed in vacuo
2. additionAqueous NaOH (10% w/v, 440 mL) was added
3. temperaturethe mixture was heated
4. temperatureat reflux 24 h
5. additionThe cooled, black solution was poured
6. customonto crushed ice
7. extractionThis mixture was extracted with EtOAc (2×)
8. washThe combined extracts were washed with brine
9. dry with materialdried (MgSO4)
10. filtrationfiltered
11. concentrationconcentrated in vacuo
12. customThe crude product was chromatographed on silica gel using 2.5% MeOH in EtOAc as eluant

ORD record

ord-b139ac1d9034428d91b7edfdecca6225

Source dataset

uspto-grants-2001_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06306891B1