Tebbe reagent reaction with norbomene

The Tebbe reagent reacts with some alkenes. The tricyclo[5.3.0.0] ring 207 was obtained nearly quantitatively by domino alkene metathesis and carbonyl alkenation of the norbomene-type ester 205 with the Tebbe reagent. This interesting reaction to give the intermediate 206 can be explained by the kinetic preference of the Tebbe reagent for the strained double bond over the ester. Alkenation of the ester in 206 produces 207. Capnellene (208) has been synthesized by applying this reaction as a key reaction [65],... 

Parallel to Schrock s efforts were those of Grubbs and co-workers.28 They studied Tebbe s reagent and found that titanacyclobutanes derived from the reagent could be isolated. For example, they found that titanacycle 18 was in direct equilibrium with metal carbene 19 (equation 11,13). This system was not an active metathesis catalyst, but the work showed that both intermediates were important in the metathesis pathway. Further work found that reaction of Tebbe s reagent with norbomene resulted in metallacycle 20, which promoted ROMP of additional equivalents of norbomene and produced a polymer that was relatively monodisperse29 (equation 11.14).30... 

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