Olefin also metathesis

The authors have found that beside metathesis, double-bond-migrating isomerization of olefins also proceeds on the irradiated Mo(CO)g/PVG. The result in Fig.8 shows production of ethene and... 

Zeolites involving transition metal ions within their framework and cavities are known to exhibit unique and fascinating properties for applications not only in catalysis but also for various photochemical processes [1,2]. Zeolites incorporated with transition metal ions in a hi ly dispersed state were found to exhibit photocatalytic reactivity for such reactions as oxidation using NO or O2 as an oxidant and the metathesis reaction of olefins. Also, the urgency of the reduction of global air pollution makes the need to address the elimination of CO as well as NO of great concern. Since CO poisons the catalysts and causes a decline in reactivity, it is vital that the reaction can proceed even in the presence of CO. 

Heterogeneous catalyst studies and factors that contributed to the discovery of the olefin disproportionation (metathesis) reaction are described. Also provided is a personal commentary on the developments of heterogeneous catalyst technology associated with this intriguing reaction and its commercialization. 

These examples illustrate the occurrence of metal contamination during mech-anochemical treatment of organic molecules without affecting the reactivity and yields, however wear in organic mechanosynthesis can also lead to incompatibility in a chemical sense, which especially holds for metal-catalyzed reactions. In a recently pubhshed demonstration of olefin cross-metathesis reaction conducted under ball-milhng conditions [33], the authors reported on an observation that the model metathesis reaction of styrene to produce stilbene proceeded with diminished... 

Olefin cross-metathesis is an intermolecular reaction between double bonds in separate molecules. Intramolecular metatheses in which two double bonds belong to the same molecule are also common and lead to ring formation. The process is called ringclosing metathesis. 

On the other hand, several groups have also recently developed asymmetric domino reactions through relay catalysis with combinations of organocatalysts with ruthenium catalysts. For example. You et al. demonstrated in 2009 that ruthenium catalyst could be compatible with Bronsted acid catalyst. They reported a practical and economical synthesis of chiral tetrahydropyrano[3,4-b]indols and tetrahydro-p-carbolines by the combination of ruthenium-catalysed olefin cross-metathesis and a chiral phosphoric acid-catalysed Friedel-Crafts alleviation reaction, as shown in Scheme 7.41. This domino reaction allowed the use of readily available materials to highly enantioselectively construct synthetically valuable polycyclic indole frameworks in enantioselectivity of up to 94% ee. 

OCT converts normal butene-2 and ethylene to polymer grade propylene via metathesis (Figure 3). The metathesis is essentially equilibrated, with the equilibrium position depending on the temperature and the ratio of reactants. In addition to the main reaction, numerous side reactions between olefins also occur which lower the yield of propylene and cause deactivation of the catalyst. 

Selectivity is also needed to produce pure products in high yields, a characteristic which is very important in the preparation of pharmaceuticals, intermediates for polymers and many other applications. Prices of chemicals vary drastically with its purity grade. Often high purity is a necessity as in polymer grade propene or olefins for metathesis. This is... 

This concept was refined by the research group of Li, who employed the thiol-yne reaction instead of the olefin cross-metathesis reaction as key step [60]. In this case, the carboxylic acid component served as anchor, whereby terminal alkynes were introduced by the remaining components (5-hexyn-l-al and propargyl isocyanoacetamide). Interestingly, thiol-yne addition of 3-mercaptopropionic acid to the pendant alkynes enabled not only the incorporation of further carboxylic acids, but also resulted in additional branching. Therefore, the second generation dendrimer, synthesized in three steps, exhibited 16 peripheral triple bonds. Moreover, this concept offers the opportunity to introduce structural diversity into the dendrimer architecture because the use of only one alkyne-functionalized compound in the Passerini-3CR still results in branching due to the thiol-yne reaction. Here, a structural sequence of employed phenylacetaldehyde and 2-nitrobenzaldehyde was demonstrated. 

Disproportionation of Olefins. Disproportionation or the metathesis reaction offers an opportunity to convert surplus olefins to other desirable olefins. Phillips Petroleum and Institut Fransais du Petrc le have pioneered this technology for the dimerization of light olefins. The original metathesis reaction of Phillips Petroleum was intended to convert propylene to 2-butene and ethylene (58). The reverse reaction that converts 2-butene in the presence of excess ethylene to propylene has also been demonstrated (59). A commercial unit with a capacity of about 136,000 t/yr of propylene from ethylene via 2-butene has been in operation in the Gulf Coast since 1985 (60,61). In this process, ethylene is first dimerized to 2-butene foUowed by metathesis to yield propylene. Since this is a two-stage process, 2-butene can be produced from the first stage, if needed. In the dimerization step, about 95% purity of 2-butene is achieved at 90% ethylene conversion. 

In this process, which has been jointly developed by Institute Francais du Petrole and Chinese Petroleum Corp., the C4 feed is mainly composed of 2-butene (1-butene does not favor this reaction but reacts differently with olefins, producing metathetic by-products). The reaction between 1-butene and 2-butene, for example, produces 2-pentene and propylene. The amount of 2-pentene depends on the ratio of 1-butene in the feedstock. 3-Hexene is also a by-product from the reaction of two butene molecules (ethylene is also formed during this reaction). The properties of the feed to metathesis are shown in Table 9-1. Table 9-2 illustrates the results from the metatheses reaction at two different conversions. The main by-product was 2-pentene. Olefins in the range of Ce-Cg and higher were present, but to a much lower extent than C5. 

Non-heteroatom-stabilised Fischer carbene complexes also react with alkenes to give mixtures of olefin metathesis products and cyclopropane derivatives which are frequently the minor reaction products [19]. Furthermore, non-heteroatom-stabilised vinylcarbene complexes, generated in situ by reaction of an alkoxy- or aminocarbene complex with an alkyne, are able to react with different types of alkenes in an intramolecular or intermolecular process to produce bicyclic compounds containing a cyclopropane ring [20]. 

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