Hydrochloric Acid → 2,3,4-Trichlorophenol

Temperatur

25 °C

Ethyl 5'-(4-formyl-3,5-dimethoxyphenoxy)valerate (13.2 g, 42.5 mmol) was dissolved in 1 n NaOH-MeOH (1:1) (100 mL) and after 10 minutes of stirring sodium borohydride (2.2 g, 60 mmol) was added portionwise over 45 minutes. After stirring two additional hours at 25° C., the solutions was chilled to 4° C., acidified with 1 N HCl to pH 5, and extracted with ethyl acetate (4×25 mL). The combined organic phases were washed with saturated aqueous NaCl (2×25 mL) and dried over MgSO4. 2,4,5-trichlorophenol (6.9 g, 35 mmol) and N,N'-dicyclohexylcarbodiimide (7.2 g, 35 mmol) were added to the ethyl acetate solution. The mixture was stirred overnight at 25° C. and then N,N-dicyclohexylurea was removed by filtration. The filtrate was washed with carbonate buffer, pH 9.5 (3.50 mL), and with saturated aqueous NaCl (2.25 mL), dried (MgSO4) and rotary evaporated. The residue was recrystallized from ethyl acetate with pentane added at 25° C. and was further chilled to -5° C. to provide a slightly orange solid (11.6 g, 25 mmol, 59% yield with respect to formyl derivative or 72% yield to trichlorophenol).

1. additionwas added portionwise over 45 minutes
2. temperaturethe solutions was chilled to 4° C.
3. extractionextracted with ethyl acetate (4×25 mL)
4. washThe combined organic phases were washed with saturated aqueous NaCl (2×25 mL)
5. dry with materialdried over MgSO4
6. stirringThe mixture was stirred overnight at 25° C.
7. customN,N-dicyclohexylurea was removed by filtration
8. washThe filtrate was washed with carbonate buffer, pH 9.5 (3.50 mL)
9. dry with materialwith saturated aqueous NaCl (2.25 mL), dried (MgSO4) and rotary evaporated
10. customThe residue was recrystallized from ethyl acetate with pentane
11. additionadded at 25° C.
12. temperaturewas further chilled to -5° C.

ORD-Eintrag

ord-54e41068eef04055a02aedb56d8f8f55

Quelldatensatz

uspto-grants-1993_03

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US05196566