[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][N:11]([C:14]2[C:19]([Cl:20])=[CH:18][C:17]([N+:21]([O-])=O)=[CH:16][N:15]=2)[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].[BH4-].[Na+]>CO.O.O.O.O.O.O.[Ni](Cl)Cl>[C:1]([O:5][C:6]([N:8]1[CH2:9][CH2:10][N:11]([C:14]2[C:19]([Cl:20])=[CH:18][C:17]([NH2:21])=[CH:16][N:15]=2)[CH2:12][CH2:13]1)=[O:7])([CH3:4])([CH3:2])[CH3:3]Place 4-(3-chloro-5-nitro-pyridin-2-yl)-piperazine-1-carboxylic acid tert-butyl ester (3.09 g, 9.01 mmol) in methanol (50 mL). Add nickel(II) chloride hexahydrate (10.7 g, 45.1 mmol) and cool the reaction to 0° C. Add sodium borohydride (5.11 g, 135.15 mmol) in portions and stir at 0° C. for 2 hours. Add CH2Cl2 and filter through a pad of Celite®. Wash filter cake with CH2Cl2 and collect filtrate. Add saturated aq. sodium bicarbonate solution to the filtrate and separate organic layer. Extract aqueous layer with CH2Cl2 (2×30 mL). Combine organic extracts, dry over Mg2SO4, filter, and concentrate under reduced pressure. Subject residue to silica gel chromatography eluting with 0-70% EtOAc:hexane to yield 1.77 g (63%) of the title compound. MS(ES): m/z=311.2 [M−H].
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