CC([O-])(C)C.[K+].[C:7]1([CH:13]([OH:17])[C:14]([CH3:16])=[CH2:15])[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1.[CH2:18](Cl)[CH:19]=[CH:20][CH3:21]>C1COCC1.[I-].C([N+](CCCC)(CCCC)CCCC)CCC>[CH2:18]([O:17][CH:13]([C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[C:14]([CH3:16])=[CH2:15])[CH:19]=[CH:20][CH3:21]Solid potassium tert-butylate (26 g, 0.228 mol) was added portion-wise (ca 15 min) to a solution of 1-phenyl-2-methyl-2-propen-1-ol (90% pure from Alfa Aesar, 25 g, 0.152 mol) in dry THF (300 ml) at room temperature under nitrogen (exothermic to 30° C.). After 1 more hour at room temperature, the reaction was cooled to 5° C. and tetra butyl ammonium iodide (2.9 g, 0.08 mol) was added followed by crotyl chloride (41.3 g, 0.456 mol) drop-wise. The reaction was warmed up to room temperature overnight and poured onto water (500 ml). The reaction was extracted twice with ethyl acetate. Each organic phase was washed with water and brine. Combined extracts were dried over solid anhydrous sodium sulfate. The solid was filtered off, rinsed with diethyl ether and the solvents were removed under vacuum. After column chromatography on silica gel (eluent: heptanes/ethyl acetate 25:1) the product was purified by bulb-to-bulb distillation (100° C./0.001 mbar). A 3:1 mixture of E/Z isomers was obtained (95% pure, 26.78 g, yield=83%).
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