[C:1]1([S:7][CH:8]2[CH2:11][CH:10]([C:12]([O:14][CH3:15])=[O:13])[CH:9]2[C:16]([O:18][CH3:19])=[O:17])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[OH:20]OS([O-])=O.[K+].[K+].S(=O)(=O)([O-])[O-].[K+].S([O-])(OO)(=O)=O.[K+].[OH2:40]>CO.ClC(Cl)C>[C:1]1([S:7]([CH:8]2[CH2:11][CH:10]([C:12]([O:14][CH3:15])=[O:13])[CH:9]2[C:16]([O:18][CH3:19])=[O:17])(=[O:20])=[O:40])[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=1To a vigorously stirred solution of 1.05 g (3.75 mmol) of dimethyl 3-(phenylthio)cyclobutane-1,2-dicarboxylate from Step A in 20 mL of methanol, was added slowly a suspension of 3.46 g (11.25 mmol) of OXONE (a commercially available mixture of sulfuric acid potassium salt and potassium hydrogen peroxymonosulfate) in 20 mL of water. The resultant cloudy suspension was stirred for 0.5 h then diluted with 50 mL of water and 100 mL of 1,2=dichloroethane. The phases were allowed to separate and the aqueous phase was extracted with 20 mL of 1,2-dichloroethane. The combined organic layers were washed with 2×50 mL of dilute aqueous sodium bicarbonate solution, 2×50 mL of water and 50 mL of brine, dried over anhydrous magnesium sulfate and concentrated to give 1.10 g (94% yield) of the title compound as a viscous oil; EI-MS, m/e (relative intensity): 281 (M+ --OCH3, 9), 171 (100), 139 (24), 111 (47); 1H NMR (CDCl3) δ2.48 (m, 1H), 2.76 (m, 1H), 3.23 (q, 1H), 3.52 (s, 3H), 3.74 (s, 3H), 3.80 (m, 1H), 3.92 (q, 1H), 7.58 (m, 2H), 7.68 (m, 1H), 7.89 (m, 2H).
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