A solution of 7-methoxy-3-(4-methoxyphenyl)-3-propylthiochroman-4-one (1.7 g, 4.96 mmol) in anhydrous tetrahydrofuran (30 ml) was cooled to −78° C. Lithium aluminum hydride (94.2 mg, 2.48 mmol) was added to this solution, followed by stirring for 12 hours at room temperature. Saturated aqueous ammonium chloride (100 ml) was added to the reaction mixture, which was then extracted twice with ethyl acetate (100 ml). The combined organic layers were washed with water and saturated aqueous sodium chloride, and then dried over anhydrous magnesium sulfate. After distilling off the solvent, zinc iodide (1.9 g, 5.95 mmol) and allyltrimethylsilane (1.57 ml, 5.95 mmol) were added dropwise to a solution of the residue in 1,2-dichloroethane (50 ml) at 0° C., followed by stirring for 12 hours at room temperature. Water was added to the reaction mixture, which was then extracted twice with dichloromethane. The combined organic layers were washed with water and saturated aqueous sodium chloride, and then dried over anhydrous magnesium sulfate. After distilling off the solvent, the residue was purified by silica gel column chromatography (eluent:ethyl acetate/hexane=1/90) to give (3RS,4RS)-7-methoxy-3-(4-methoxyphenyl)-4-(2-propenyl)-3-propylthiochroman (1.32 g, Yield 72%).
