[CH3:1][N:2]([CH3:23])[C:3]([NH:5][C:6]1[CH:11]=[C:10]([O:12][C:13]2[C:14]([CH3:22])=[N:15][C:16]([N+:19]([O-])=O)=[CH:17][CH:18]=2)[CH:9]=[CH:8][N:7]=1)=[O:4].[NH4+].[Cl-]>CO.C1COCC1.CCOC(C)=O.[Zn]>[NH2:19][C:16]1[N:15]=[C:14]([CH3:22])[C:13]([O:12][C:10]2[CH:9]=[CH:8][N:7]=[C:6]([NH:5][C:3](=[O:4])[N:2]([CH3:23])[CH3:1])[CH:11]=2)=[CH:18][CH:17]=1
A mixture of 1,1-dimethyl-3-(4-((2-methyl-6-nitropyridin-3-yl)oxy)pyridin-2-yl)urea (5.2 g, 16.4 mmol) in MeOH (60 mL) and THF (60 mL) was treated with NH4Cl (26.3 g, 492 mmol) and stirred vigorously at RT. Zinc dust (10.72 g, 164 mmol) was added portion-wise and the mixture was stirred at RT for 2 h. Additional portions of NH4Cl (5 g, 93 mmol) and zinc dust (1 g, 15 mmol) were added and stirring was continued overnight. The mixture was diluted with EtOAc and filtered. The filtered solids were washed with EtOAc. The combined filtrates were further filtered (2×) and concentrated to dryness. THF (150 mL) and thiol-modified silica gel (1.4 mmol/g loading, 22 g, 31 mmol) were added and the mixture was stirred at RT overnight. The solids were removed by filtration and washed with THF. The combined filtrates were concentrated to dryness to give 3-(4-((6-amino-2-methylpyridin-3-yl)oxy)pyridin-2-yl)-1,1-dimethylurea (4.54 g, 96%) as a foam. MS (ESI) m/z: 288.1 (M+H+).
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