General procedure for the synthesis of 7-amino-2(3H)-benzoxazolone from 5-chloro-7-nitrobenzo[d]oxazol-2(3H)-one: Compound 6 (4 g, 18.56 mmol) was dissolved in a 4:1 MeOH/DMF solvent mixture (50 ml) and 10% Pd/C catalyst (500 mg) was added. The hydrogenation reaction was carried out at 60 psi hydrogen pressure overnight. The progress of the reaction was monitored by TLC (unfolding agent ratio ethyl acetate:petroleum ether = 3:7). After completion of the reaction, the reaction mixture was filtered through a diatomaceous earth pad and the filtrate was concentrated under vacuum. The crude product was crystallized with ether to give 2.8 g of beige solid in 99% yield. The structure of the product was confirmed by 1HNMR (DMSO-d6, 200 MHz): δ5.31 (2H, bs, NH2), 6.26 (1H, dd, J = 7.6 Hz, J'= 1 Hz, Ar-H), 6.38 (1H, dd, J = 8.4 Hz, J'= 1.2 Hz, Ar-H), 6.80 (1H, t, J = 8 Hz, Ar-H), 11.32 (1H, bs, NH).
