1.80 g (4.85 mmol) of ethyltriphenylphosphonium bromide are initially introduced in 8 ml of THF at 0° C., and 533 mg (4.75 mmol) of potassium tert-butoxide are added. After 1.5 h at RT, a solution of 1.16 g (3.23 mmol) of 5-[4-(4-propylcyclohexyl)phenyl]selenophene-2-carbaldehyde in 7 ml of THF is added, and the batch is stirred for 2.5 h. The mixture is diluted with MTBE, and sat. ammonium chloride soln. and 2 N hydrochloric acid are added. The organic phase is separated off, and the aqueous phase is extracted with MTBE. The combined organic phases are washed with sat. sodium chloride soln. and dried using sodium sulfate. The solution is concentrated to dryness, and the residue is purified by column chromatography (SiO2, n-heptane→n-heptane:EtOAc=20:1). 2-(Propenyl)-5-[4-(4-propylcyclohexyl)phenyl]selenophene is obtained as an E/Z isomer mixture.
