Internal olefins, metathesis

To summarize, experimental evidence has been advanced regarding hydride involvement in the initiation step of olefin metathesis with certain catalysts. One concept considers the source of the hydride to be external—that is, originating from a promoter or a cocatalyst. A second concept assumes a hydride being generated internally from the metathesizing olefin. It is quite possible that both concepts are operative. 

Quite recently, ruthenium carbene complexes more typically known as olefin metathesis catalysts have been shown to act as alkyne hydrosilylation catalysts.78,79 7Vzz r-addition is the major product with trialkylsilanes, even in a single example with an internal alkyne.78 This result represents one of the very few examples of fra r-hydrosilylation of internal alkynes. 

MI1 18th International Symposium on Olefin Metathesis and Related... 

The polystyrene-bonded complexes Pol—CH2—( -CsfLt)—W(CO)3R (R = H, Cl, Me), when activated by -BuAlCl2, are reported to be highly active for the metathesis of internal olefins, though accompanied by double-bond migration reactions74. 

A number of insect sex pheromones are long-chain internal olefins or their epoxides and can be prepared via metathesis reactions, for example the reaction of dec-l-ene with pentadec-l-ene to give tricos-9-ene, the cis isomer of which is a sex pheromone of the housefly (Musca domestica)173.174. see ajso Kiipper and Streck175,176. 

Frechet and Liang synthesised a fifth-generation benzyl ether dendrimer with 22 internal allyl groups. Subsequent olefin metathesis [1] led on the one hand to intramolecular linking, and on the other hand to creation of a covalent linkage site for olefin-functionalised guests (Fig. 6.1) [2]. In this way, intermolecular cross-linking - between G5 dendrimer molecules - could also be attained. 

In 1967, Calderon, Chen, and Scott4) reported a homogeneous catalyst system comprised of tungsten hexachloride, ethanol, and ethylaluminum dichloride would disproportionate internal olefins. These authors used the term olefin metathesis to describe the reaction. At room temperature 2-pentene was transformed in one to three minutes into a mixture containing, at equilibrium, 25, 50, and 25 mole per cent of 2-butene, 2-pentene, and 3-hexene, respectively. Double-bond isomerization was not detected and a quantitative reaction selectivity was obtained. Additional reports by Calderon and cowor-... 

Brandli and Ward prepared a library of internal olefins through self-metathesis and CM of a variety of derivatives of oleic acid, namely, methyl oleate, oleic acid, oleyl amine (which did not react), oleyl alcohol, and other olefins [42], These reactions were performed using 1 mol% of C3 and led to statistical product mixtures that were analyzed by GC-MS and NMR. 

Rush, S., Reinmuth, A. and Risse, W., in proceeding of International Symposium on Olefin Metathesis and Related Chemistry, Durham, UK, Abstracts, P50. 

Acetylenic monomers also appeared to undergo polymerisation with conventional olefin metathesis catalysts. This relates to monosubstituted highly branched alkylacetylenes and arylacetylenes as well as disubstituted acetylenes (internal alkynes) [16-18], It has been demonstrated that acetylene itself may also be polymerised using olefin metathesis catalysts [19,20]. The polymerisation of alkynes [scheme (2)] involves a metathesis reaction [scheme (5) of Chapter 2] analogously to that of cycloolefins [21] ... 

Metathesis of Cycloolefins. The same general catalysts which promote the ring-opening polymerization of cycloolefins are also effective in the olefin metathesis reaction in which acyclic internal olefins undergo a unique redistribution process (1, 2, 5, 6). 

---