C(OP([CH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)(=O)OCC)C.C([Li])CCC.[CH2:21]([O:23][C:24]([CH:26]1[CH:28]([CH:29]=O)[C:27]1([CH3:32])[CH3:31])=[O:25])[CH3:22].O>O1CCCC1.CCCCCC>[CH2:21]([O:23][C:24]([CH:26]1[CH:28]([CH:29]=[CH:9][C:10]2[CH:11]=[CH:12][CH:13]=[CH:14][CH:15]=2)[C:27]1([CH3:31])[CH3:32])=[O:25])[CH3:22]22.8 g (0.1 mol) of benzylphosphonic acid diethyl ester were dissolved in 400 ml of absolute tetrahydrofuran and the solution was cooled to -70° C. 0.11 mol of n-butyl-lithium (as a 15% strength solution in hexane) were added dropwise under a counter-current of nitrogen and while stirring well; the mixture was then stirred at -70° C. for a further 15 minutes, and thereafter 18.6 g (0.1 mol) of 2,2-dimethyl-3-formyl-cyclopropanecarboxylic acid ethyl ester were added dropwise at -65° C., again still under nitrogen. The reaction mixture was then allowed to come to room temperature and was stirred further for 3 hours at 25° C. Thereafter, the reaction batch was poured into 2 liters of water and extracted with 600 ml of ether. The ether phase was dried over sodium sulphate and the solvent was then stripped off in vacuo. The oily residue was distilled at 145°-150° C./3 mm Hg. 2,2 -Dimethyl-3-(2-phenyl-vinyl)-cyclopropanecarboxylic acid ethyl ester having a refractive index nD23 of 1.5022 was obtained in 69.6% yield.
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