(Ethoxy-ethoxycarbonyl-methyl)-triphenyl-phosphonium chloride (3.79 g, 8.8 mmol) and potassium carbonate (1.46 g, 10.6 mmol) were added to a solution of 4-benzyloxy-2-methyl-benzaldehyde (0.8 g, 3.5 mmol) in isopropanol (10 ml) at 10° C. under an argon atmosphere [for the preparation of (ethoxy-ethoxycarbonyl-methyl)-triphenyl-phosphonium chloride see: K. K. Bach, H. R. El-Seedi, H. M. Jensen, H. B. Nielsen, I. Thomson, K. B. G. Torssell, Tetrahedron 1994, 50, 7543-7556]. The suspension was heated to 60° C. After 12 h and after 20 h (ethoxy-ethoxycarbonyl-methyl)-triphenyl-phosphonium chloride (each time 3.79 g, 8.8 mmol) and potassium carbonate (each time 1.46 g, 10.6 mmol) were added again. After 36 h the suspension was filtered off and the filtrate was evaporated under reduced pressure. The residue was dissolved in dichloromethane, washed with saturated aqueous ammonium chloride and ice water and dried over sodium sulfate. The solvent was removed under reduced pressure and the residue purified by column chromatography (silica gel, dichloromethane) to give 0.7 g (2.1 mmol, 58%) of the title compound as yellow liquid.
