[Cl:1][C:2]1[CH:3]=[C:4]([CH:6]=[CH:7][C:8]=1[S:9]([CH3:12])(=[O:11])=[O:10])[NH2:5].[N:13]([O-])=O.[Na+].O.O.[Sn](Cl)Cl.[OH-].[Na+]>Cl.O>[ClH:1].[Cl:1][C:2]1[CH:3]=[C:4]([NH:5][NH2:13])[CH:6]=[CH:7][C:8]=1[S:9]([CH3:12])(=[O:11])=[O:10]
To a stirred suspension of 3-chloro-4-(methylsulfonyl)aniline (3.0 g, 15.0 mmol, Ish. K. Khanna et al., J. Med. Chem. 40, 1619 (1997)) in 20% aqueous HCl (20 mL) was added dropwise a solution of sodium nitrite (1.1 g, 16.0 mmol) in water (20 mL) below −5° C. After stirring for 1 hour at that temperature, tin(II) chloride dihydrate in 20% aqueous HCl (20 mL) was added dropwise below −5° C. The resulting suspension was stirred for 1 h at room temperature. The mixture was basified with aqueous NaOH (pH=14) and extracted with CHCl3 (200 mL×2), dried over MgSO4, and concentrated in vacuo. The solid (5 g) was dissolved in 10% methanolic HCl (30 mL), and volatiles were removed by evaporation. The residue was washed with ethanol to give the title compound (1.3 g, 34%).
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