[CH:1]([N:4]1[CH2:9][CH2:8][N:7]([C:10]2[CH:15]=[CH:14][C:13]([N+:16]([O-])=O)=[CH:12][N:11]=2)[CH2:6][CH2:5]1)([CH3:3])[CH3:2].CCO.O.N>[Fe].CC(O)=O>[CH:1]([N:4]1[CH2:5][CH2:6][N:7]([C:10]2[N:11]=[CH:12][C:13]([NH2:16])=[CH:14][CH:15]=2)[CH2:8][CH2:9]1)([CH3:3])[CH3:2]A mixture of iron powder (1.4 g, 25.3 mmol, 4 equiv), 1-isopropyl-4-(5-nitro-pyridin-2-yl)piperazine (1.58 g, 6.32 mmol), EtOH (20 mL), H2O (5 mL), and AcOH (2.5 mL) is stirred for 2 h at 90° C., allowed to cool to RT, basified by addition of aqueous ammonia, filtered through a pad of celite and partially concentrated to remove EtOH. The aqueous residue is saturated with sodium chloride and extracted with EtOAc and DCM. The combined organic phase is washed with brine, dried (Na2SO4), filtered and concentrated. The residue is purified by silica gel column chromatography (DCM/MeOH/NH3aq, 91:8:1) to afford the title compound as a purple solid: ESI-MS: 221.1 [MH]+; TLC: Rf=0.20 (DCM/MeOH/NH3aq, 91:8:1).
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