Styrene compounds carbon-alkene reactions

Carbon radicals generated by the addition of enol radicals derived from 1,3-dicarbonyl compounds to alkenes are efficiently trapped by oxygen in a chain reaction leading to hemiperacetals [51], The process is illustrated by the electrochemical or AIBN-initiated reaction of 2-methyl-1,3-cyclopentanedione with styrene and oxygen in acetonitrile, which provides the thermodynamically favored all-c bicyclic peroxide in good yield (Scheme 23) [51],... 

Lewis acid-catalyzed addition of carbonyl compounds to alkenes is an important method for forming new carbon-carbon bonds. Lewis acid-promoted ene and Baylis-Hillman reactions have been well documented. Notably, boron trihalide-mediated aryl aldehyde-styrene coupling reactions proceed in a different way (Scheme 23.17). Boron trihalide acts simultaneously as a Lewis acid and as a reactant to regioselectively produce l,3-dihalo-l,3-diarylpropane (synlanti = 50/50). 

Rhodium(III) tetra(/ -sulfonatophenyl)porphyrin [(TSPP)Rh] aquo and hydroxo complexes react with a series of alkenes in water to form /3-hydroxyalkyl coordination compounds. Addition reactions of (TSPP)Rh-OH to unactivated terminal alkenes CH2=CHR invariably occur with both kinetic and thermodynamic preferences to place rhodium on the terminal carbon to form (TSPP)Rh-CH2CH(OH)R complexes. Acrylic and styrenic alkenes initially react to place rhodium on the terminal carbon to form [Rh]-CH2CH(OH)R as the kinetically preferred isomer, but subsequently proceed to an equilibrium distribution of regioisomers where [Rh]-CH(CH2OH)R is the predominant thermodynamic product. Equilibrium constants for reactions of the diaquo rhodium(III) compound [(TSPP)Rhm(H20)2]3 in water with a series of terminal alkenes that form /9-hydroxyalkyl complexes were directly evaluated and used in deriving thermodynamic values for addition of the Rh-OH unit to alkenes. The AG° for reactions of the Rh-OH unit with alkenes in water was found to be approximately 3 kcalmol-1 less favourable than the comparable Rh-H reactions in water.100... 

The classical Vilsmeier-Haack reaction - involves electrophilic substitution of a suitable carbon nucleophile with a chloromethyleneiminium salt, for example salt (1). Suitable carbon nucleophiles are generally electron-rich aromatic compounds such as V,N-dimethylaniline (2), alkene derivatives such as styrene (3) or activated methyl or methylene compounds such as 2,4,6-trinitrotoluene (4 Scheme I). These compounds (2-4) react with salt (1) giving, after loss of hydrogen chloride, the corresponding im-inium salts (5-7). Hydrolysis of iminium salt (5) affords aldehyde derivative (8) and this transformation (Ar—H - Ar—CHO) is the well-known Vilsmeier-Haack formylation reaction. Hydrolysis of iminium... 

Solvent effects on, and products from, reaction of styrene with ethylene in the presence of di-)ti-chloro-dichlorobis(styrene)dipalladium(n), [Pd-(Ph CH—CH2)Cl2]2, indicate a mechanism similar to (i)->(iv) above, with the addition of a preliminary equilibrium between the dimer and solvated monomers. The mechanism of reaction of styrene with vinyl compounds, catalysed by the same chloride-bridged dipalladium complex, has been studied using isotopic tracer (H, D) experiments. Palladium-acetate-catalysed reaction of styrene with benzene, also investigated using deuterium tracer experiments, involves no hydride shift, in contrast to the rather closely related Wacker process. The importance of intermediates with palladium-carbon n-bonds in palladium(ii)-catalysed alkylation and arylation of alkenes has been demonstrated. 

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