Bromoacetyl bromide → 3-Oxo-3,4-dihydro-2H-1,4-benzoxazine-6-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

3-amino-4-hydroxybenzoic acid (4.0 g, 26.0 mmol) was dissolved in 168 mL of chloroform. 92 mL of saturated sodium bicarbonate solution was added and the new bi-phase mixture was stirred vigorously and cooled to 0° C. using an ice bath. Bromoacetylbromide (3.42 mL, 39 mmol) was added drop-wise. Fifteen minutes later the solution was removed from the ice bath and maintained at room temperature for 48 hours. HPLC (Eclipse XDB-C18, 4.6×250 mm, 5 micron, 1-99% CH3CN/H2O with 0.1% trifluoroacetic acid) chromatogram indicated that all of the starting material was gone and a new peak (Rt=3.7 min) had formed. The reaction mixture was quenched using concentrated hydrochloric acid until the solution reached a pH of 2. The organic layer was separated and the aqueous phase was extracted with 100 mL of chloroform. The combined organic layers were treated with 75 mL of 10% hydrochloric acid solution and separated once again. The organic phase was dried over Na2SO4, filtered and concentrated to give 3-oxo-3,4-dihydro-2H-1,4-benzoxazine-6-carboxylic acid (4.8 g, 24.7 mmol, 95%) as an off-white amorphous solid. MS (ES) m/e 194 [M+H]+.

Provenance & Evidence