1.3 g of sodium hydride, 50% in mineral oil, were suspended in 20 ml of abs. dimethyl sulphoxide (DMSO) and treated dropwise at 15° C. with a solution of 8.6 g of diethyl (4-carbethoxybenzyl)-phosphonate in 25 ml of abs. DMSO. The mixture was stirred at room temperature for 1 hour and then a solution of 3.3 g of the above aldehyde in 25 ml of abs. DMSO and 10 ml of tetrahydrofuran was added dropwise thereto. After stirring at 40° C. for 2 hours the mixture was poured into ice-water, acidified with 2N hydrochloric acid and extracted with ethyl acetate. After drying the organic phase with sodium sulphate and evaporation of the solvent the crude product was filtered over a silica gel column (eluent hexane/5% methyl tert.butyl ether). After recrystallization from hexane/ethyl acetate there were obtained 4.4 g of ethyl (E)-4-[2-(5,5,8,8-tetra-methyl-3 -propoxy-5,6,7,8 -tetrahydro-naphthalen-2-yl)vinyl]benzoate in the form of white crystals, melting point 97°-100° C.
