Ethylparaben → Ethyl 3-bromo-4-hydroxybenzoate

Temperatur

-15 °C

This procedure is modified from the work of Oberhauser (J. Org. Chem, 1997, 62, 4504). To a solution of 4-hydroxybenzoic acid ethyl ester (57.8 g, 348 mmol) in 480 mL of dry acetonitrile was added HBF4 Et2O (54% in Et2O, 32.9 mL). The solution was cooled to −15° C. with an ice/methanol bath. N-bromosuccinimide (67.2 g, 378 mmol) was added portionwise at a rate where the temperature would not rise above −10° C. After addition was complete, the cooling bath was removed and the reaction mixture was allowed to stir overnight at room temperature. Worked up by pouring the reaction mixture into aqueous sodium bisulfite (38%, 200 mL) and extracting four times with ethyl acetate. The organic layers were combined, washed with water, saturated brine, dried over anhydrous sodium sulfate, decanted, and concentrated in vacuo to give a white solid. Recrystallization from ethyl acetate/hexane gave 3-bromo-4-hydroxybenzoic acid ethyl ester (70.7 g, 83%) as a white solid. 1H NMR (300 MHz, CDCl3) δ 1.39 (t, J=6.7 Hz, 3H, —CO2CH2CH3), 4.34 (t, J=6.7 Hz, 2H, —CO2CH2CH3), 7.02 (d, 1H, arom), 7.91 (dd, 1H, arom), 8.19 (d, 1H, arom).

1. customrise above −10° C
2. additionAfter addition
3. customthe cooling bath was removed
4. additionby pouring the reaction mixture into aqueous sodium bisulfite (38%, 200 mL)
5. extractionextracting four times with ethyl acetate
6. washwashed with water, saturated brine
7. dry with materialdried over anhydrous sodium sulfate
8. customdecanted
9. concentrationconcentrated in vacuo
10. customto give a white solid
11. customRecrystallization from ethyl acetate/hexane

ORD-Eintrag

ord-ce8caf06272c41ebb9678b94e6d40d8a

Quelldatensatz

uspto-grants-2006_03

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US07008636B2