Diene syntheses norbomene derivs

The results of the investigated cross-metathesis reactions of silicon containing norbomene derivatives with ethylene showed a poor reactivity for some substituents. Reactive chlorosilanes act as catalyst poisons and silazanes diminish the catalyst s activity by coordination of nitrogen to the metal center. Starting from norbomene derivatives with alkoxy-substituted silicon moieties, a selective synthesis of new silicon-containing a,(0-dienes could be accomplished (Scheme 2). 

A comonomer for the synthesis of ethylene/propene elastomers - 2-ethylidene-norbomene (7) - is synthesised via a Diels-Alder cycloaddition of cyclopenta-diene and butadiene followed by an isomerization with titanium-based catalysts of the intermediate 2-vinyl derivative 6 in excellent yield (98 %) (eq. (12)) [22]. 

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