[C:1]([N:5]1[CH2:10][CH2:9][N:8]([C:11]2[CH:16]=[CH:15][C:14]([N+:17]([O-])=O)=[CH:13][CH:12]=2)[CH2:7][CH2:6]1)([CH3:4])([CH3:3])[CH3:2].O.O.[Sn](Cl)Cl.Cl>CO>[C:1]([N:5]1[CH2:10][CH2:9][N:8]([C:11]2[CH:12]=[CH:13][C:14]([NH2:17])=[CH:15][CH:16]=2)[CH2:7][CH2:6]1)([CH3:4])([CH3:2])[CH3:3]1-tert-Butyl-4-(4-nitro-phenyl)-piperazine (348 mg, 1.32 mmol) is dissolved in MeOH (10 mL) and tin (II) dichloride dihydrate (1.08 g, 4.79 mmol) is added. The mixture is cooled using a water bath and conc. HCl is added (3 mL). The reaction is stirred at 40° C. overnight. After removing the methanol, the resultant solution is basified using conc. NaOH (pH 11). The water phase is extracted with diethyl ether (3×) and the organic layers combined, dried over MgSO4, filtered, concentrated in vacuo to afford the title compound (308 mg, 99%) which is used in the next step without further purification. LCMS: Rt 2.16 min (87%)
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