Ethylene Glycol → 2-methyl-2-[p-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)propenyl]-phenyl]-1,3-dioxolane

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Reaction Steps

3.0 g of 4'-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)propenyl]-acetophenone (prepared as described in Example 22) dissolved in 40 ml of benzene are treated with a catalytic amount of p-toluenesulphonic acid and 0.6 g of ethyleneglycol and warmed in a Dean-Stark apparatus, the water formed being concurrently separated off. After heating under reflux for 2 days, the mixture is cooled down, introduced into ice/saturated sodium bicarbonate solution and exhaustively extracted with ether. The ether extract is washed twice with a saturated sodium chloride solution, dried over sodium sulphate and evaporated under reduced pressure to remove the solvent. The oily residue is purified by adsorption on silica gel using hexane/ether (9:1) for the elution. The 2-methyl-2-[p-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)propenyl]-phenyl]-1,3-dioxolane obtained from the eluate melts at 122°-123° C. after recrystallisation from ether.

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