[Br-].[CH2:2]([P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)[C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.C([Li])CCC.[C:33]1(=O)[CH2:38][CH2:37][C:36](=[O:39])[CH2:35][CH2:34]1>C1COCC1.CCCCC>[CH:2](=[C:33]1[CH2:34][CH2:35][C:36](=[O:39])[CH2:37][CH2:38]1)[C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1To a mechanically stirred suspension of 15.24 g (0.035 mole) of benzyltriphenylphosphonium bromide in 150 ml of THF there was added first 22 ml of 1.61 N n-butyllithium in pentane and then 5.0 g (0.032 mole) of cyclohexane-1,4-dione, ethylene monoketal in 50 ml of THF. Following 5 hours' heating at reflux the mixture was allowed to cool and was then washed in turn with water and brine. The organic layer was concentrated, and the residue was chromatographed on 1 liter of silica gel, eluting with 20% ethyl acetate in Skellysolve® B, to afford 7.15 g (97%) of 4-benzylidenecyclohexanone, ethylene ketal as an oil, the nmr spectrum of which is in consonance with the structure.
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