18-Crown 6-Ether

In a nitrogen-filled atmosphere, [Ir(cod)Cl]₂ (2.7 mg, 0.0040 mmol), the ligand (4.3 mg, 0.0080 mmol), KF (12 mg, 0.20 mmol), 18-crown-6 (53 mg, 0.20 mmol) and a Teflon-coated magnetic stirring bar are added to a 1-dram vial. Then, anhydrous THF (0.40 mL) is added. The mixture is stirred for 5 min. at ambient temperature before allyl carbonate derivative (0.20 mmol) and the silyl enolate derivative (0.40 mmol, 2.0 equiv) are added. The vial is sealed with a cap and stirred at 50 °C for 12 h. Then, water (1 mL) is added to the reaction mixture followed by 1 N HCl (0.5 mL). The resulting mixture is stirred vigorously for 3 h at room temperature. Brine (1 mL) and Et₂O (1 mL) are added; the organic layer is separated, and the aqueous layer is extracted with Et₂O (3 x 3 mL). The combined organic extracts are dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure. Purification of the crude product is performed by flash　column chromatography (gradient elution: hexane:Et₂O = 50:1 to 5:1) to provide the product.