[NH:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH2:4][CH2:3][CH2:2]1.[N+:11]([O-])([OH:13])=[O:12].C(=O)([O-])[O-].[K+].[K+].CCOC(C)=O>S(=O)(=O)(O)O>[N+:11]([C:8]1[CH:9]=[C:10]2[C:5]([CH2:4][CH2:3][CH2:2][NH:1]2)=[CH:6][CH:7]=1)([O-:13])=[O:12]To a solution of 1,2,3,4-tetrahydroquinoline (6.5 g, 0.049 mol) in concentrated sulfuric acid (118 ml) cooled to 0° C. was added a solution of concentrated nitric acid (4.9 ml) in concentrated sulfuric acid (12 ml) dropwise over 0.3 h so as to maintain the temperature at 0-5° C. On completion of addition, the reaction mixture was poured onto crushed ice then neutralised with solid potassium carbonate. EtOAc (500 ml) was added and the mixture was filtered to remove undissolved solids then extracted with further EtOAc (4×500 ml). The combined extracts were dried over MgSO4 and concentrated in vacuo to give the crude product which was purified by flash column chromatography. Elution with 5% EtOAc/60-80° C. petroleum ether gave the title compound as an orange solid (5.46 g). 1H NMR (250 MHz, CDCl3) δ(ppm): 7.40 (dd, 1H), 7.26 (d, 1H), 7.02 (d, 1H), 4.16 (br, 1H), 3.35 (m, 2H), 2.81 (t, 2H), 1.95 (m, 2H).
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