Hydrochloric Acid → 4-Bromo-1,3-benzoxazole

Temperature

90 °C

Following a literature procedure (Org. Prep. & Proc. Int. 22(5), 613 (1990)), a solution of 2-amino-3-bromophenol (800 mg, 4.25 mmol) and trimethylformate (0.685 mL, 6.25 mmol) in methanol (1.25 mL) was treated with concentrated hydrochloric acid (0.01 mL). The flask was fitted with a short path distillation apparatus. The temperature of the solution was slowly raised to 90° C. and maintained until the methanol had finished distilling. Upon cooling, the residue crystallized and was dissolved in diethyl ether (70 mL). This solution was successively washed with 5% sodium hydroxide solution and water and dried over anhydrous magnesium sulfate. After filtering, the solvents were removed by rotoevaporation and the residue was purified by flash column chromatography on silica gel eluted with 20% ethyl acetate in hexanes to yield the title compound (550 mg, 65% yield).

1. customThe flask was fitted with a short path distillation apparatus
2. distillationhad finished distilling
3. temperatureUpon cooling
4. customthe residue crystallized
5. dissolutionwas dissolved in diethyl ether (70 mL)
6. washThis solution was successively washed with 5% sodium hydroxide solution and water
7. dry with materialdried over anhydrous magnesium sulfate
8. filtrationAfter filtering
9. customthe solvents were removed by rotoevaporation
10. customthe residue was purified by flash column chromatography on silica gel
11. washeluted with 20% ethyl acetate in hexanes

ORD record

ord-615d296676a342c294e4519b12ae5b41

Source dataset

uspto-grants-2001_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06291511B1