[OH:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[O:17][C:12]3=[N:13][CH:14]=[CH:15][CH:16]=[C:11]3[C:10](=[O:18])[CH:9]=2)=[CH:4][CH:3]=1.[CH3:19][C:20](OC(C)=O)=[O:21].O>CN(C1C=CN=CC=1)C.N1C=CC=CC=1>[C:20]([O:1][C:2]1[CH:3]=[CH:4][C:5]([C:8]2[O:17][C:12]3=[N:13][CH:14]=[CH:15][CH:16]=[C:11]3[C:10](=[O:18])[CH:9]=2)=[CH:6][CH:7]=1)(=[O:21])[CH3:19]In a 50 mL round-bottomed flask fitted with condenser and magnetic stirrer were placed 2-(4-hydroxy-phenyl)-pyrano[2,3-b]pyridin-4-one (1.5 g, 6.27 mmol), Ac2O (700 mg, 6.89 mmol) and a catalytic amount of DMAP (50 mg) in pyridine (10 mL) and the reaction mixture was stirred for 16 h at rt. The reaction mixture was poured into water and extracted with ethyl acetate. The organic layer washed with water, dried and concentrated to give a 2-(4-acetoxyphenyl)-pyrano[2,3-b]pyridin-4-one (930 mg, 53%).
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