Cyclopentanes Divinylcyclopentanes

Polynorbomene is more difficult to degrade. Ethene in the presence of a tungsten carbene catalyst does bring about some reduction in MW (factor of five) but no 1,3-divinylcyclopentane is detected (Wagener 1991a). This is another example of the protection against metathesis offered by substituents on the carbons adjacent to the double bonds, in this case in the form of cyclopentane rings. 

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