Norbomene 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]... 

In this strategy, an ally 1 group is attached to the substrate bound silicon that then reacts in a cross metathesis fashion with (2a). Then this surface bound Ru-alkylidene catalyzes ROMP of norbomene to give alkyl silicon terminated polymer film that is thus attached to the surface in controllable density and polymer thickness. 

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. ... 

Studies of this kind fall broadly into two groups as indicated in Table 15.1. Those labelled P are mainly concerned with the effect of small quantities of acyclic olefin M2 on the MW, yield, and cis content of the polymer produced from the cyclic olefin Mi in this case the ratio [M2]/[Mi] is usually 0-0.05. Those labelled T involve the use of much higher proportions of M2 (with [M2]/[Mi] 0.5-2), with the object of producing telomers with well-defined end-groups, in some cases for synthetic purposes. For example, highly substituted cyclopentane and tetrahydro-fiiran derivatives can be readily made by the cross-metathesis of substituted norbomenes or 7-oxanorbomenes with hex-3-ene or l,4-dimethoxybut-2-ene catalyzed by ruthenium carbene complexes (Schneider, M.F. 1996). If the acyclic olefin is unsymmetrical and represented by Q Q, where Q and are the alkylidene moieties, three series of telomers may be produced, Q (Mi) Q, Q (Mi) Q, Q (Mi) Q, where ti is the number of Mi units. The lowest members of the series (n= 1) are dienes, and it is sometimes possible to deteet, separate, and identify the cc, ct, and tt isomers. 

The synthesis of a,co-difunctional telomers by cross-metathesis between cyclic olefins and acyclic functionalized olefins is possible in the presence of functional-group-tolerant catalysts. Thus, cross-metathesis of dimethyl hex-3-enedioate with cycloocta-1,5-diene (Pinazzi 1980 Reyx 1982b, 1990), cyclopentene (Reyx 1986, 1987), or norbomene (Cramail 1991a) in the presence of the catalyst system WCV Mc4Sn allows the synthesis of a,m-difunctional oligomers, e.g. reaction (2). 

We have seen that end-groups may be detected by C NMR spectra and inferred from mass spectra. Other methods for the detection of end-groups in the products of cross-metathesis of cyclic and acyclic olefins include IR and UV spectra, and elementary analysis. For example, polymers of norbomene made in the presence of pent-l-ene show a band at 1375 cm attributable to methyl groups, and bands at 905 and 990 cm due to vinyl groups (Porri 1974). Such bands become stronger relative to the main band as [M2]/[Mi] is increased, thereby reducing the MW. Polymers of cyclopentene made in the presence of 5-(j3-naphthoxypent-l-ene) have... 

In this paper we report the cross-metathesis of cycloolefins with ethylene (ethenolysis). We present the selective synthesis of linear silicon-containing a,o>olefins starting with norbomene derivatives containing alkyl-, amine- or alkoxy-substituted silicon moieties and ethylene (Scheme 2). 

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. 

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). 

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

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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