[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]C=2)[CH2:6][CH2:5]1)([CH3:3])[CH3:2].[CH3:19][CH2:20]O.O.[NH3:23]>[Fe].CC(O)=O>[CH:1]([N:4]1[CH2:5][CH2:6][N:7]([C:10]2[N:23]=[CH:12][C:13]([NH:16][C:20]3[CH:19]=[CH:15][CH:14]=[CH:13][CH:12]=3)=[CH:14][CH:15]=2)[CH2:8][CH2:9]1)([CH3:2])[CH3:3]A mixture of 1-isopropyl-4-(4-nitro-phenyl)-piperazine (Step 33.2) (1.58 g, 6.32 mmol), iron (1.4 g, 25.3 mmol, 4 equiv), EtOH (20 mL), H2O (5 mL) and AcOH (2.5 mL) was stirred for 2 h at 90° C. The reaction mixture was allowed to cool to rt, basified by addition of aqueous NH3, filtered through a pad of celite. The filtrate was concentrated (to remove EtOH), extracted with EtOAc and DCM, saturated with NaCl and extracted with DCM. The organic phase was washed with brine, dried (Na2SO4), filtered and concentrated. Purification of the residue by silica gel column chromatography (DCM/MeOH/NH3aq, 91:8:1) afforded 1.1 g of the title compound as a purple solid: ESI-MS: 221.1 [M+H]+; TLC: Rf=0.20 (DCM/MeOH/NH3aq, 91:8:1).
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