[Br-].[CH3:2]C([P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)/C=C/C.O1[CH2:30][CH2:29][CH2:28][CH2:27]1.C([Li])CCC.[CH3:36]/[C:37](=[CH:40]\[C:41](\[CH3:44])=[CH:42]\[CH3:43])/[CH:38]=O>CCCCCC.O>[CH3:27][C:28]([CH:36]=[C:37]([CH3:38])[CH:40]=[C:41]([CH3:44])[CH:42]=[CH:43][CH3:2])=[CH:29][CH3:30]
(1-Methyl-2(E)-butenyl)triphenylphosphonium bromide from Example 9 (0.62 g, 0.0015 mole) was added to a dry flask with 5 ml tetrahydrofuran. The flask was equipped with magnetic stirrer and septum; the reaction was carried out under nitrogen. The salt did not dissolve completely but became a sticky suspension. The mixture was cooled over ice, and butyllithium (2.5 M in hexane) was added dropwise, with stirring, until the color change became permanent; then an additional 0.0015 mole was added. The solid in the flask dissolved as it was converted to the ylide. One hundred milligrams of (2E,4E)-2,4-dimethyl-2,4hexadienal (0.0008 mole), compound 15, a previously known compound (Patel and Pattenden, 1985), was added to the Wittig reagent, and the mixture was allowed to warm to room temperature. The mixture was stirred for 2 hr, and it was again cooled over ice. Water was added dropwise until the red color of the solution had disappeared, and ca. 2 ml more water was added. The mixture was diluted with hexane and the organic layer dried over sodium sulfate. The solvent was removed and the product passed through a silica column with hexane. By capillary GC the product was 61% the (E,E,E,E) isomer, ca. 31% the (E,E,Z,E) isomer, and ca. 8% by-products, after clean-up on silica. Further purification on the AgNO3HPLC column yielded the (E,E,E,E) isomer in >97% purity.
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