Styrene codimerization

Hydrovinylation reactions of vinylarenes, Eq. (1), have been investigated most extensively because of the importance of 3-aryl-1-butenes as potential intermediates for widely used anti-inflammatory 2-arylpropanoic acids [4]. Since the first report of a high pressure (1000 atm) ethylene/styrene codimerization in the presence of RhClj [5] various metals such as Ru [6], Co [7],Pd [8],andNi [9,... 

Phenyl-1,4-hcxadicnc (122) is obtained as a major product by the codimerization of butadiene and styrene in the presence of a Lewis acid[110]. Pd(0)-catalyzed addition reaction of butadiene and aiiene (1 2) proceeds at 120 C to give a 3 1 mixture of trans- and c -2-methyl-3-methylene-l,5.7-octatriene (123)[lll]. 

Asymmetric Codimerization of Styrene with Ethylene Influence of the Complex Anion of the Catalyst on Optical Yield... 

Finally, in the codimerization of styrene with ethylene to optically active 3-phenyl-1-butene (52) (Table XI), it has been shown that the complex anion (Y) can exert a strong influence on the optical yield 103, 105). 

However, in the presence of iridium siloxide and bulky substituents at the silicon in vinylsilanes instead of silylative coupling, the codimerization (hydrovi-nylation) of styrene and vinylsilanes occurs according to Equation 14.13 ... 

The hydrovinylation reaction, the codimerization of ethene and styrene (Scheme 2), provides easy access to chiral building blocks from inexpensive hydrocarbon feedstocks, which can be used further for the preparation of fine chemicals. Key problems in this reaction include the selectivity of the reaction and the stability of the catalyst. The main side reactions are oligomerization and isomerization of the product to internal achiral alkenes. The latter reaction can be suppressed by... 

Nickel allyl complexes in the presence of chiral bidentate ligands catalyze the enantioselective codimerization of ethylene with norbornene and with styrene 129... 

While rare-earth metals are proven powerful olefin polymerization catalysts [21-24], there are only limited reports on controlled olefin oligomerizations or selective olefin dimerizations utilizing these elements [204,207,208], An ansa-scandocene [207] and the bis(indenyl)yttrium complex 41 (Fig. 25) [204] were reported to produce head-to-tail dimers from monosubstimted aliphatic alkenes (57). Complex 41 produces predominantly the tail-to tail adduct with styrene. The codimerization of an aliphatic alkene (including substrates containing various functionalities) with styrene affords tran -tail-to-tail dimers, apparently as a result of 1,2-insertion of the a-olefin followed by 2,1-insertion of styrene directed by the phenyl group (58). 

When isopropylidenecyclqnopane (29a equation 10) or diphenylmethylenecyclt ropane (29b) is used, the codimerizations with alkenes such as ethylene, styrene or norbomene giving alkyiidene-cyclopentanes are achieved under mild conditions in more than 75% yields. ... 

Codimerization of styrene and ethylene giving 3-phenyl-l-butene is another example of asymmetrically induced hydrovinylation. With catalyst precursors obtained from (jt-allyl)NiX or (> 3-cyclooct-5-enyl)NiX (X = various anions) modified with bis(menthyl)methylphosphane. ]<)- and (S)-3-phenyl-1 -butene in up to 37% ee is obtained, depending on the counterion X of the catalytic system13. 

Pd complexes of soluble P,0-fimctionalized carbosilane dendrimers (8) were used by Vogt and co-workers for the hydrovinylation reaction (codimerization of ethylene and styrene). This C-C coupling reaction is of great interest, because it opens an easy access to building blocks for fine chemicals as well as pharmaceuticals [Eq. (6)] [16]. 

For the codimerization of ethylene and styrene, a pressure membrane reactor was developed and the reaction ran almost without any isomerization of the products or formation of side products. These undesired side reactions are often observed at high conversion. Nevertheless, the space-time yield dropped to zero within 15 residence times and low retention of the dendrimer as well as precipitation of palladium on the membrane were found. Larger dendritic catalysts with higher retentions did not show much improvement, indicating that catalyst deactivation was indeed the major problem. 

Codimerization of acetylenes and allyl halides to give 1,4-pentadiene derivatives can be carried out using polymer-supported palladium(II) chloride catalystPd(OAc>2 bound to diphenylphosphinated styrene-divinylbenzene polymer has been applied to the oligomerization of butadiene to give 1,7-octadiene and higher oligomers. ... 

Barlow reported some examples of codimerization using the catalyst dichlorobis(benzonitrile)palladium [49]. The reaction of styrene and methyl acrylate yielded the straight-chain isomer methyl lrans-5-phenyl-4-pentenoate (Equation 48). 

Styrene and ethylene were successfully codimerized by palladium chloride [49]. The major product was /ran -l-phenyl-1-butene (90%), but also 2-phenyl-2-butene (5%) and l-phenyl-2-butene (5%) were present (Equation 55). These codimers were obtained in yields up to 45%. 

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