The general procedure for the synthesis of 4-amino-3-methoxycarbonylbenzoic acid from methanol and 2,4-dioxo-2,4-dihydro-1H-benzo[1,3]oxazine-6-carboxylic acid is as follows: 150 mg (1.21 mmol) of 4-dimethylaminopyridine was added to 2.5 g (12.1 mmol) of 2,4-dioxo-1,4-dihydro-2H-3,1-benzo oxazine-6-carboxylic acid (for literature description see J. Med. Chem., 1981, 24(6), 735-742) in a mixture of 10 ml of dimethylformamide and 10 ml of methanol. The reaction mixture was heated at 60°C for 3 hours. After completion of the reaction, the reaction mixture was concentrated under reduced pressure. The residue was dissolved in water and extracted with ethyl acetate. The organic phase was washed with saturated sodium chloride solution, dried over anhydrous sodium sulfate and subsequently concentrated under reduced pressure. The solid obtained was dissolved in ethyl acetate, filtered and dried to give 1.98 g of a white powdery product in 84% yield with a melting point of 224.5 °C.
![2,4-Dioxo-2,4-dihydro-1H-benzo[d][1,3]oxazine-6-carboxylic acid](/CAS/GIF/77423-13-3.gif)
