[I-].[CH3:2][S+](C)(C)=O.[H-].[Na+].[CH3:9][C:10]1([CH3:23])[C:14]([CH3:15])=[CH:13][CH2:12][CH:11]1[C:16]1[CH2:21][CH2:20][C:19](=[O:22])[CH2:18][CH:17]=1>CS(C)=O.C(OCC)C>[CH3:9][C:10]1([CH3:23])[C:14]([CH3:15])=[CH:13][CH2:12][CH:11]1[C:16]1[CH2:21][CH2:20][C:19]2([O:22][CH2:2]2)[CH2:18][CH:17]=1Trimethylsulfoxonium iodide (4.78 g, 21.63 mmol.) is added in portions to a suspension of sodium hydride (60% in mineral oil, 1.00 g, 25.54 mmol.) in DMSO (10 ml). Stirring is carried out for 30 minutes before 4-(2,2,3-trimethyl-cyclopent-3-enyl)-cyclohex-3-enone (XIII, see U.S. Pat. No. 5,189,013, 2.78 g, 13.64 mmol.), dissolved in DMSO (10 ml), is added. When the addition is complete, stirring is continued for a further 30 minutes, and then the reaction solution is poured onto ice (25 ml). The mixture is diluted with diethyl ether (50 ml), the phases are separated, and the aqueous phase is extracted three times with diethyl ether (50 ml each time). The combined organic phases are washed once with saturated NaCl solution before being dried over Na2SO4, filtered off and concentrated in a rotary evaporator. 3.08 g of crude product are obtained, which is then purified by flash chromatography (cyclohexane/EtOAc=20:1, Rf=0.22). 2.21 g of a colourless oil are obtained.
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