[N+:1]([O-:4])(O)=[O:2].[N:5]1[CH:10]=[CH:9][CH:8]=[C:7]2[C:11]3[CH:12]=[CH:13][CH:14]=[CH:15][C:16]=3[CH2:17][C:6]=12>S(=O)(=O)(O)O>[N+:1]([C:14]1[CH:13]=[CH:12][C:11]2[C:7]3[C:6](=[N:5][CH:10]=[CH:9][CH:8]=3)[CH2:17][C:16]=2[CH:15]=1)([O-:4])=[O:2]A ca. 10° C.-cold mixture of nitric acid (65%, 1.1 mL) and sulfuric acid (96%, 1.6 mL) is added dropwise to a solution of 9H-indeno[2,1-b]pyridine (2.44 g) in sulfuric acid (96%, 3 mL) chilled in an ice bath. The solution is stirred in the cooling bath for 1 h and poured then onto crushed ice. The precipitate formed is separated by filtration and the filtrate is neutralized using 4 M aqueous NaOH solution. The precipitate formed is separated by filtration and combined with the precipitate separated before. The precipitate is triturated with acetone and dried to give the title compound as a solid. Yield: 2.64 g (85% of theory); LC (method 1): tR=2.93 min; Mass spectrum (ESI+): m/z=213 [M+H]+.
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