1968 Volume 41 Issue 5 Pages 1232-1236
Phytone (XI), an important intermediate in the preparation of α-tocopherol, was synthesized by a selective Wittig reaction between geranyltriphenylphosphonium halide (VII) and the aldehyde group of 2-methyl-6-oxoheptanal (VIII), followed by the hydrogenation of the product. VIII was prepared from 1,3-dimethyl-1-cyclohexene (V) by ozonolysis and reductive decomposition. V could not be obtained in a pure state by the dehydration of 2,6-dimethylcyclohexan-1-ol (II), presumably because of the isomerization of the intermediate carbonium ion. The pyrolysis of the acetate of II (III) was found to give pure V. That the hardly-pyrolizable stereoisomer of III was cis,cis-2,6-dimethylcyclohexyl-1-acetate (VI) is consistent with the cis-elimination mechanism.
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