N1C=CC=CC=1.[CH3:7][CH:8]([CH2:17][CH2:18][CH:19]=[C:20]([CH3:27])[CH2:21][CH2:22][CH:23]=[C:24]([CH3:26])[CH3:25])[CH:9]([OH:16])[CH2:10][C:11]([O:13][CH2:14][CH3:15])=[O:12].O=[Cr](=O)(O[Cr](=O)([O-])=O)[O-].[NH+]1C=CC=CC=1.[NH+]1C=CC=CC=1>O.[O-2].[O-2].[O-2].[Cr+6]>[CH3:7][CH:8]([CH2:17][CH2:18][CH:19]=[C:20]([CH3:27])[CH2:21][CH2:22][CH:23]=[C:24]([CH3:25])[CH3:26])[C:9](=[O:16])[CH2:10][C:11]([O:13][CH2:14][CH3:15])=[O:12]To a mixture of pyridine (132 ml) and ethyl 3,7,11-trimethyl-6,10-dodecadien-2-ol-1-carboxylate (132 g), the Cornforth reagent (prepared by adding dropwise a solution of chromium trioxide (223 g) in water (150 ml) to pyridine (2230 ml) while cooling with ice water) is added, and the resultant mixture is allowed to stand at room temperature. After removal of the precipitate by filtration, the reaction mixture is admixed with water and extracted with ether. The ether extract is washed with water, dried and evaporated. The residual material is distilled under reduced pressure to give ethyl 3,7,11-trimethyl-6,10-dodecadien-2-one-1-carboxylate (75 g) as a pale yellow oil. B.P. 125° to 129°C/0.06 mmHg. IR: 1740, 1225 cm-1 (COO); 1710 cm-1 (C=O). NMR (carbon tetrachloride): δ 1.25 (m), 1.61 (s), 1.69 (s), 1.98 (s), 2.0-2.8 (m), 3.33 (s), 4.15 (m), 4.8-5.25 (m).
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