Trifluoroacetic acid → 7-Methoxy-2H-1,4-benzoxazin-3(4H)-one

Participants

Reaction Conditions

Reaction Steps

2-amino-5-methoxy-phenol hydrochloride (4.0 g, 22.8 mmol) was dissolved in 100 mL of chloroform in a 500 mL round-bottom flask and treated with 80 mL of saturated sodium bicarbonate solution. This mixture was stirred rapidly and was cooled to 0° C. in an ice bath. A solution of bromoacetyl bromide (2.98 mL, 34.2 mmol) in 20 mL of chloroform was added slowly. After 2 hours, HPLC (Eclipse XDB-C18, 4.6×250 mm, 5 micron, 1-99% CH3CN/H2O with 0.1% trifluoroacetic acid) showed that all of the starting material (Rt=2.4 min) was consumed and that a major product peak had formed (Rt=4.5 min). The reaction was diluted with 200 mL of chloroform and 200 mL of water. The layers were separated and the aqueous layer was extracted with chloroform (3×150 mL). The combined organic layers were dried over magnesium sulfate, filtered, and concentrated to a red-brown solid. This solid was dissolved in 200 mL of anhydrous DMF, treated with potassium carbonate (3.2 g, 22.8 mmol) and heated to 85° C. After two hours, HPLC showed that all of the material had converted to a new product (Rt=4.4 min), so the reaction mixture was allowed to cool to room temperature and was poured into 700 mL of water. The aqueous phase was extracted with ethyl acetate (3×200 mL) and the combined organic layers were washed with water (3×500 mL) and saturated NaCl (1×200 mL), dried over magnesium sulfate, filtered, and concentrated to give 7-(methyloxy)-2H-1,4-benzoxazin-3(4H)-one (1.42 g, 7.9 mmol, 34%) as a red-orange solid. MS (ES) m/e 180 [M+H]+.

Provenance & Evidence