[N+:1]([C:4]1[CH:5]=[C:6]([CH:14]=[C:15]([N+:17]([O-])=O)[CH:16]=1)[CH2:7][O:8][CH2:9][C:10]([O:12][CH3:13])=[O:11])([O-])=O.C([O-])(O)=O.[Na+]>CO>[NH2:1][C:4]1[CH:5]=[C:6]([CH:14]=[C:15]([NH2:17])[CH:16]=1)[CH2:7][O:8][CH2:9][C:10]([O:12][CH3:13])=[O:11]A mixture of 2.1 (5.0 g, 18.5 mmol), SnCl2 dihydrate (48.0 g, 212.7 mmol) in 60 mL of methanol was refluxed for 40 minutes. The resulting dark solution was cooled (ice bath) and cautiously neutralized by adding saturated NaHCO3. The solid precipitate was filtered off and washed with methanol and CH2Cl2 until no product was found (by TLC) in the washings. The filtrate and washings were combined and evaporated in vacuo to give crude diamine 2.2. Chromatography on a silica gel column (4.5×20 cm) eluting with ethyl acetate afforded the title compound as a yellow oil (2.5 g, 64%), which slowly crystallized upon drying in vacuo: 1H NMR (CDCl3) δ 6.11 (d, J=2 Hz, 1H, C4 --H), 5.96 (t, J=2 Hz, 2H, C2 --H), 4.44 (s, 2H, CH2), 4.07 (s, 2H, CH2), 3.75 (s, 3H, CH3), 3.59 (br s, 4H, NH2); 13C NMR (CDCl3) δ 170.96, 147.78, 139.33, 105.51, 101.41, 73.31, 66.85, 51.89.
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