[Br:1][C:2]1[CH:3]=[CH:4][C:5]([F:21])=[C:6]([C@@:8]2([CH3:20])[NH:16][C:15](=O)[C:11]3([CH2:14][CH2:13][CH2:12]3)[S:10](=[O:19])(=[O:18])[CH2:9]2)[CH:7]=1.COC1C=CC(P2(SP(C3C=CC(OC)=CC=3)(=S)S2)=[S:31])=CC=1.C([O-])(O)=O.[Na+]>O1CCOCC1>[Br:1][C:2]1[CH:3]=[CH:4][C:5]([F:21])=[C:6]([C@@:8]2([CH3:20])[NH:16][C:15](=[S:31])[C:11]3([CH2:14][CH2:13][CH2:12]3)[S:10](=[O:19])(=[O:18])[CH2:9]2)[CH:7]=1To a solution of (R)-7-(5-bromo-2-fluoro-phenyl)-7-methyl-5,5-dioxo-5λ6-thia-8-aza-spiro[3.5]nonan-9-one (1.1 g, 2.92 mmol, Eq: 1.00) in dioxane (50 ml) was added Lawesson's reagent (1.18 g, 2.92 mmol, Eq: 1.00). The reaction mixture was stirred at 80° C. for 2 hours. More Lawesson's reagent (1.55 g, 3.84 mmol, Eq: 1.00) was added and stirring continued at 80° C. for 8 hours. The reaction mixture was poured into sat. NaHCO3 solution and extracted twice with ethyl acetate. The organic layers were washed with brine, dried over Na2SO4, filtered and evaporated to give light yellow oil. The residue was chromatographed on 20 g silica gel with 0-50% ethyl acetate in heptane to give (R)-7-(5-bromo-2-fluoro-phenyl)-7-methyl-5,5-dioxo-5λ6-thia-8-aza-spiro[3.5]nonan-9-thione (1.05 g, 2.68 mmol, 91.5% yield) as a light yellow foam. MS (ISP): m/z=392.0 [M+H]+ and 394.3 [M+2+H]+.
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