Ethylene olefin metathesis

Olefin Metathesis. The olefin metathesis (dismutation) reaction (30), discovered by Eleuterio (31), converts olefins to lower and higher molecular weight olefins. For example, propylene is converted into ethylene and butene... 

Table 8-5 indicates the wide variety of catalysts that can effect this type of disproportionation reaction, and Figure 8-7 is a flow diagram for the Phillips Co. triolefm process for the metathesis of propylene to produce 2-butene and ethylene. Anderson and Brown have discussed in depth this type of reaction and its general utilization. The utility with respect to propylene is to convert excess propylene to olefins of greater economic value. More discussion regarding olefin metathesis is noted in Chapter 9. 

Molybdenum allyl complexes react with surface OH groups to produce catalysts active for olefin metathesis.34 35 Using silica as a support for the heterog-enization of Ti and Zr complexes for the polymerization of ethylene did not give clear results.36 In these cases, HY zeolite appeared to be a more suitable support. The comparable productivity of the zeolite-supported catalyst with... 

The metal-catalysed olefin metathesis (equation 122) when applied to dienes results in ring-closure and expulsion of an olefin (equation 123). Thus the molybdenum carbene complex 241 promotes the decomposition of the 1,6-heptadiene derivative 242 to a mixture of the cyclopentene 243 and ethylene (equation 124)122. An analogous reaction of the alcohol 244 gives 245 (equation 125), and 4-benzyloxy-l,7-decadiene (246) affords the cyclohexene 247 and 1-butene (equation 126). These transformations, which occur in benzene at room temperature, proceed in excellent yields122. 

Ethylene-alkyne metathesis, 26 955-956 Ethylene-a-olefin copolymers,... 

Olefin metathesis technology, in polymer synthesis, 26 944-948 Olefin oligomerization, 16 111 Olefin oxides, alkanolamines from (with ammonia), 2 122-140 Olefin polymerization, organic titanium compounds in, 25 122 Olefin(ic) polymers, 17 699-709 ethylene-propylene elastomers, 17 705-707... 

Such higher order prerequisites could be fulfilled by ensemble operation of several sites. For example, a dimeric cluster of cuprous ions on silica gel is very active for the oxidation of CO with NzO at room temperature, but isolated cuprous ions are entirely inactive for this reaction 60). More interesting selectivity may be found in the reaction of olefins with methylene complexes the reaction of olefins with mononuclear methylene undergoes an olefin metathesis reaction, but the reaction of ethylene with bridging methylene in /i-CH2Co2(CO)2(Cp)2 61), /<-CH2Fe2(CO)8 (62), and /<-CH2-/i-ClTi(Cp)2Al(Me)2 (65) (Cp = cyclopentadiene) leads to propene formation (homologation reaction). 

The first catalysis of an olefin metathesis reaction was reported by Banks and Bailey in 1964 (56). They reported that activated molybdenum hexacarbonyl on alumina converted propylene, for example, into ethylene and 2-butene at 150°C and 30 atm. Oxides of rhenium are also powerful heterogeneous catalysts. 

Scheme 14. Ring-closing olefin metathesis of 62 detached the allyl glycoside 63. A cross-metathesis with 64 and ethylene liberated target-oligosaccharides such as 65 in form of their n-pentenyl glycosides.

Along with diene and diyne metathesis, ene-yne metathesis has also been employed to form macrocycles. This type of metathesis is performed with the catalysts used for olefin metathesis, and the yields are improved in the presence of ethylene, which forms the highly reactive [Ru]=CH2 species. Shair and coworkers took advantage of this reaction twice in the course of their total synthesis of longithorone A [40]. When ene-ynes 51 and 52 are treated with ruthenium complex G1 under an atmosphere of... 

Olefin metathesis was first observed in the 1950s, and was used in industry to convert propylene to a mixture of but-2-ene and ethylene. This Phillips Triolefin Process used an aluminum/molybdenum catalyst whose exact structure was unknown. 

Applications of the olefin metathesis reversible chemical reaction, discovered by Phillips Petroleum in the 1960s, were also developed in the subsequent years. By this reaction, Arco produces propylene from ethylene and butene-2 Hercules prepares its plastic, Metton, from dicyclopentadiene and Shell synthesizes its C12-C14 SHOP (Shell Higher Olefin Process) alcohols used for detergents. 

Olefin metathesis has become one of the most important large-scale technical processes for the manufacture of olefins in the petrochemical industry [123]. When cyclic olefins are used as substrates, high-molecular polymers, which are formed by the so-called ring-opening metathesis (ROM), have found applications as elastomers and plastics. Gas-phase studies on the mechanism of olefin metathesis had been confined to simple metal carbenes, for example [Mn=CH2]+, [Fe=CH2]+,and [Co=CH2]+ [124-127]. Most of the metatheses have been observed with deuterated ethylene. 

Olefin metathesis offers a means of shifting olefins to olefins with a different number of carbon atoms. Olefin metathesis is the disproportionation or dismutation of olefins over a catalyst, usually based on molybdenum or tungsten. For example, propylene gives ethylene and... 

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