Norbomenes ring-opening cross-metathesis

Mo(OR )2(NAr)(=CHR) [C2Ciim]Cl-AlCl3 Ring-opening cross-metathesis of norbomene with allyltrimethylsilylsilane product extracted with hexane conversion after one hour at RT ca. 80%, selectivity for the disilylated product ca. 75%. [24]... 

Cross-metathesis of trialkoxy- and trisiloxy-substituted vinylsilanes [21] as well as octavinylsilsesquioxane [15] with vinyl sulfides proceeds efficiently but only in the presence of the 2nd generation Grubbs catalysts (IV) to offer a new and very attractive route for syntheses of [alkyl(aiyl)]sulfide-substituted vinylsilanes and vinyl-silsesquioxane with high preference for the -isomer, as illustrated by exclusive isolation of such isomers. The Fischer-type ruthenium carbene complex Ru(=CHSPh)Cl2(PCy3)2 has recently been reported as an effective catalyst in the ring opening/cross-metathesis of norbomene derivatives with vinyl sulfide [22], suggesting that these carbenes can be reactive in the cross-metathesis. 

Complex 10 is a very active catalyst for ring-opening cross-metathesis of norbomene derivatives. ... 

The ruthenium NHC complex (53) has been reported to catalyse the enantioselective ring-opening cross-metathesis of norbomenes with allyltrimethylsilane (<98% ee)P ... 

For the selectivity of the cross-metathesis reaction with ethylene (ethenolysis) the choice of a suitable catalyst and a cycloolefin for which ring-opening is energetically favorable as well as the optimization of the reaction conditions are crucial. Cycloolefins with a norbomene skeleton were chosen for their high ring strain. The silicon-containing educts can be obtained by hydrosilylation of norbomadiene with the corresponding silanes. 

Finally this type of reaction can be run as a sequence of ring opening and cross metathesis. For example, the norbomene derivative in Equation 21.15 imdergoes reaction with the vinylsilane to generate the optically active cyclopentane in high enantiomeric excess. ... 

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