[CH3:1]C(C)([O-])C.[K+].[O:7]1[C:11]2[CH:12]=[CH:13][CH:14]=[CH:15][C:10]=2[CH:9]=[C:8]1[CH:16]=O>O1CCCC1.[Br-].C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.CN(C)C=O>[CH:16]([C:8]1[O:7][C:11]2[CH:12]=[CH:13][CH:14]=[CH:15][C:10]=2[CH:9]=1)=[CH2:1]92 ml of a 1N solution of potassium tert-butoxide in tetrahydrofuran are added dropwise to a vigorously stirred mixture at 0° C. of 68.4 mmol of benzofuran-2-carboxaldehyde and 92 mmol of methyltriphenylphosphonium bromide in 200 ml of tetrahydrofuran and 150 ml of dimethylformamide. The medium is stirred for 2 h at room temperature, poured into 2 liters of ice-water and extracted with ether. After concentration of the solvents, the residue is taken up in 1 liter of petroleum ether and the precipitate is filtered off and washed with petroleum ether. The expected product is obtained by evaporation of the filtrate.
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