[CH3:1][CH:2]([CH2:12][CH:13]=C)[CH2:3][O:4][CH2:5][C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1.I([O-])(=O)(=O)=[O:16].[K+]>CC(C)=O.O.[Os](=O)(=O)(=O)=O>[CH2:5]([O:4][CH2:3][C@H:2]([CH3:1])[CH2:12][CH:13]=[O:16])[C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1A 250 mL round-bottomed flask, equipped with a magnetic stirring bar and a thermometer was fitted with a septum and a nitrogen inlet. The apparatus was charged with benzyl 2-methyl-4-penten-1-yl ether (2.39 g, 12.5 mmol) in 75 mL of acetone and 25 mL of water. Osmium tetroxide (0.833 mL of an 0.15M aqueous solution, 0.125 mmol) was added in one portion, followed by potassium periodate (6.04 g, 26.2 mmol) in three equal portions. The resulting slurry was stirred for 6 hours at room temperature and decanted into a 500 mL separatory funnel. The aqueous layer was extracted with 3×200 mL of diethyl ether. Each washing was stirred over the solids for 5 minutes, washed with 150 mL of saturated aqueous sodium thiosulfate and 100 mL of saturated aqueous sodium chloride. The combined organic layers were dried over sodium sulfate, filtered, concentrated and chromatographed (4×20 cm column; 4:1 hexane:ethyl acetate) to afford 1.94 g (81%) of aldehyde 4 as a colorless oil. Rf =0.37 (4:1 hexane:ethyl acetate).
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