C(Cl)(Cl)(Cl)Cl.O=[C:7]1[CH2:10][CH:9]([S:11]([O:14][CH2:15][CH2:16][CH2:17][CH3:18])(=[O:13])=[O:12])[CH2:8]1.[C:19]([O:27][CH2:28][CH3:29])(=[O:26])[CH2:20][C:21]([O:23][CH2:24][CH3:25])=[O:22].N1C=CC=CC=1>C1COCC1.CCCCCC.Cl[Ti](Cl)(Cl)Cl.C(OCC)(=O)C>[CH2:15]([O:14][S:11]([CH:9]1[CH2:10][C:7](=[C:20]([C:21]([O:23][CH2:24][CH3:25])=[O:22])[C:19]([O:27][CH2:28][CH3:29])=[O:26])[CH2:8]1)(=[O:13])=[O:12])[CH2:16][CH2:17][CH3:18]TiCl4 (0.5 mL, 4.854 mmol) was added to a solution of THF (25 mL) and CCl4 (5 mL) at 0° C. This was followed by the addition of butyl 3-oxocyclobutane-1-sulfonate (0.5 g, 2.42 mmol) at 0° C. and diethyl malonate (0.38 mL, 2.42 mmol). The resulting mixture was stirred at 0° C. for 5 minutes. Then pyridine (0.78 mL, 9.68 mmol) in THF (10 mL) was added and stirred at room temperature for 96 hours. The reaction was monitored by TLC (30% ethyl acetate in hexane). The reaction mixture was partitioned between water and ethyl acetate. The organic layer was washed with sodium bicarbonate solution, brine solution, dried over anhydrous Na2SO4 and concentrated. Purification by column chromatography on silica gel (13% ethyl acetate in hexane) afforded 200 mg of the product (25% yield).
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