Dehydration of Cyclic Ethers and Epoxides

The dehydration of oxolanes yields dienes. 2,5-Dimethylcyclohexadienes are selectively formed by ring-opening dehydration of 2,2,5,5-oxolane over platinum/Al203, AI2O3 or NaY zeolite. Bartok and Molnar found that ( )-2,2,3,4,5,5-hexamethyl oxolane (I) is converted mainly into 2,3,4,5-tetramethylhexa—1,5-diene (IV), whUe its meso-isomer (II) reacts at a higher rate than (I) to rive 2,3,4,5-tetramethylhexa— 2,4-deiene (III) with high selectivity on 7-alumina.Mutual isomerization of the dienes is not observed. 

Cyclohexeneoxide is dehydrated to 1,3-cyclohexadiene with i02 — Ti02 — MgO in liquid phase at 381 

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