[N+:1]([O-:4])(O)=[O:2].[CH3:5][C:6]1([CH3:26])[C:10](=[O:11])[O:9][C:8]2[CH:12]=[CH:13][C:14]3[C:19]([C:7]1=2)=[CH:18][C:17]([CH2:20][N:21]1[CH:25]=[N:24][CH:23]=[N:22]1)=[CH:16][CH:15]=3.C(OC(=O)C)(=O)C.C(=O)([O-])O.[Na+]>C(OCC)(=O)C>[CH3:5][C:6]1([CH3:26])[C:10](=[O:11])[O:9][C:8]2[CH:12]=[CH:13][C:14]3[C:19]([C:7]1=2)=[CH:18][C:17]([CH2:20][N:21]1[CH:25]=[N:24][CH:23]=[N:22]1)=[C:16]([N+:1]([O-:4])=[O:2])[CH:15]=3Nitric acid (72% by weight, 0.045 ml) was added dropwise to a stirred, ice-cooled mixture of 1,1-dimethyl-8-(1H-1,2,4-triazol-1-ylmethyl)-2(1H)-naphtho[2,1-b]furanone (0.44 g) and acetic anhydride (6 ml). The mixture was stirred at room temperature for 18 h, then added to a stirred mixture of aqueous sodium hydrogen carbonate solution and ethyl acetate. The organic phase was separated, dried and evaporated to dryness under reduced pressure, and the residue was purified by flash chromatography. Elution with ethyl acetate:pentane, 3:1 v/v, gave 1,1-dimethyl-7-nitro-8-(1H-1,2,4-triazol-1-ylmethyl)-2(1H)-naphtho[2,1-b]furanone, m.p. 183°-185° after recrystallisation from ethyl acetate. (Example 13).
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