Br[CH2:2][CH2:3][CH:4]=[C:5]([CH3:7])[CH3:6].[Mg].[C:9]1([C:15]2([CH2:20][CH2:21][CH2:22][C:23](=[O:25])[CH3:24])[O:19][CH2:18][CH2:17][O:16]2)[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=1.[NH4+].[Cl-]>CCOCC.CCCCCCC.CCOCC>[CH3:24][C:23]([OH:25])([CH2:2][CH2:3][CH:4]=[C:5]([CH3:7])[CH3:6])[CH2:22][CH2:21][CH2:20][C:15]1([C:9]2[CH:10]=[CH:11][CH:12]=[CH:13][CH:14]=2)[O:19][CH2:18][CH2:17][O:16]1A Grignard reagent of 3.50 g (0.021 mol) of 5-bromo-2-methyl-2-pentene in 13 ml of ether and 0.62 g (0.026 mol) of magnesium turnings in 14 ml of ether was added slowly at −25° under N2 to a stirred solution of 5.54 g (0.024 mol) of 5-(2-phenyl-1,3-dioxolan-2-yl)-2-pentanone obtained under b) in 20 ml of ether. During the introduction, the temperature was left rising up to −5° C. and the reaction mixture left stirring for 45 min. Then a saturated solution of NH4Cl was added and the formation of a white precipitate was observed. Extraction with ether (2×), washing with water (3×), drying (Na2SO4) and concentrating gave 6.24 g of the crude product. Column chromatography (SiO2, heptane/ether 7:3) gave 2.53 g (38%) of a yellow oil.
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