Acetic Acid → 1-(3,4-Dichlorophenyl)-1H-imidazole-4-carboxylic acid

Temperature

60 °C

A mixture of 3,4-dichloroaniline (24.3 g, 150 mmol), triethyl orthoformate (24.0 g, 162 mmol), ethyl nitroacetate (20.0 g, 150 mmol) and acetic acid (1 ml) was refluxed for 1 h. After addition of additional triethyl orthoformate (300 ml, 1.8 mol), iron powder (25.1 g, 450 mmol) and acetic acid (300 ml, 5.2 mol) the mixture was refluxed for 5 h. During this time, additional iron powder (25.1 g, 450 mmol) was added in 3 portions. The mixture was cooled to 60° C. and AcOEt (1 l) was added. After refluxing for 10 min, the precipitate was filtered and the filtrate was concentrated. Residual acetic acid was azeotropically removed by co-evaporation with toluene (500 ml). The crystalline residue was dissolved in dioxane (300 ml), 2N NaOH solution (300 ml) and charcoal (ca. 10 g) was added. The mixture was refluxed for 2 h, filtered and cooled to 5° C. HCl solution (37%) was added until precipitation was complete. Filtration and drying afforded the title compound (25.8 g, 67%) as light brown crystalline material. Mp. >235° C. dec. (H2O), MS: m/e=255 [(M−H)−]

1. temperaturewas refluxed for 1 h
2. temperaturewas refluxed for 5 h
3. temperatureAfter refluxing for 10 min
4. filtrationthe precipitate was filtered
5. concentrationthe filtrate was concentrated
6. customResidual acetic acid was azeotropically removed by co-evaporation with toluene (500 ml)
7. dissolutionThe crystalline residue was dissolved in dioxane (300 ml)
8. addition2N NaOH solution (300 ml) and charcoal (ca. 10 g) was added
9. temperatureThe mixture was refluxed for 2 h
10. filtrationfiltered
11. temperaturecooled to 5° C
12. additionHCl solution (37%) was added until precipitation
13. filtrationFiltration
14. customdrying

ORD record

ord-ebb0faa573b649168c911204c92674f3

Source dataset

uspto-grants-2004_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06683097B2