Synthesis of Styrene

The chemical industry consumes styrene, the monomer used for the manufacture of polystyrene in large quantities each year. The coiiimonly used 

A new synthesis developed by Chapman uses a single step to convert mixed xylenes (compounds that are noncarcinogenic) into styrene. This new method eliminates the use of ton quantities of benzene each year (details of this process are not available). 

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Unfortunately, the highest enantioselectivity so far obtained for the synthesis of styrene oxide by this route is only 57 % ee with Goodman s sulfide 30 [21]. Thus methylidene transfer is not yet an effective strategy for the synthesis of terminal epoxides. 

A prime example of these features can be found in the synthesis of styrene/ (meth)acrylate random copolymers. By controlling the initiator/total monomer ratio, the molecular weight can be accurately controlled for both styrene/methyl methacrylate and styrene/butyl acrylate random copolymers. As can be seen in Figure 2.3 the polydispersity for both systems is essentially 1.10-1.25 over comonomer ratios ranging from 1/9 to 9/1. 

Scheme 7.3 The synthesis of styrene oxides through the enzymatic acylation of chloroalcohols.

There is increasing interest in studying the alkylation of methylbenzenes in the side chain with methyl alcohol over zeolite catalysts.270 These reactions may lead to new nontraditional technologies in the synthesis of styrene from toluene and that of p-methy I styrene from p-xylene. A one-step route from toluene or p-xylene to the corresponding styrenes would be of great practical importance compared with the presently practiced two-step syntheses (alkylation followed by dehydrogenation). 

An industrial process for the synthesis of styrene through the transformation of 4-vinylcyclohexene the other possible cyclodimer has been developed. 

The alkene arylation reaction has been extensively studied by Moritani and coworkers462 and by Heck.463 An interesting application of this chemistry is the synthesis of styrene from the oxidative coupling of benzene and ethylene (equation 189).464... 

The first workable capping agents for controlled radical polymerization were discovered by Rizzardo et al. [77, 78] who used nitroxides. The nitroxide reacts reversibly with radical chain ends but itself does not initiate the monomer. They called their new system Stable Free Radical Polymerization (SFRP). Scheme 32a depicts an example of SFRP using TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy). SFRP was developed independently by Georges at Xerox for the synthesis of styrene block polymer as dispersing agents [79]. 

Pyrazole-based COX-inhibitors were synthesized using Pd/C as a heterogeneous and ready-filterable palladium source. Electron-deficient boronic acids coupled well while orf/zo-substitulcd and electron-rich boronic acid were less reactive (Scheme 62) [146]. The same team also developed a two-step and one-pot procedure for the synthesis of styrene-based nicotinic acetylcholine receptor antagonists. 

Two types of asymmetric reactions were conducted synthesis of styrene oxide and reduction of olefinic ketones. 

Y. Xu, P. C. Painter and M. M. Coleman, Polymer, FIGURE 7-46 Synthesis of styrene/vinyl phenol... 

Synthesis of styrene. The alkylation of toluene with methanol over a CsX-zeolite catalyst produces a mixture of ethylbenzene and styrene (Equation (9)). 

The synthesis of styrenic block copolymers (SBCs) has been discussed in a number of books and review articles concerning block copolymers [1] and anionic polymerization [2]. A comprehensive review of the field is beyond the scope of this chapter, the objective of which is to provide an overview of the technology, with particular emphasis on processes currently used for commercial production. 

Di Maina et al. °° recently described a direct synthesis of styrene-isobutene block copolymers based on the use of AKII3 in CH2Q2- This brief report underlines that the polymeriation of styrene, initiated by traces of isobutene in the presence of AICI3, proceeds without appreciable termination and transfer reactions. A more detailed account of these interesting experiments was announced by the authors and should provide an explanation of some still intriguing futures, particularly concerning the role of traces of isobutene in promoting the onset of styrene pol merisation. 

Sample Problem 18.7 Design a synthesis of styrene from ethylbenzene. 

Figure 14.25 Synthesis of styrene-butadiene rubber (SBR) by grafting from copolymerization.

Scheme 2.4 Addition polymerization synthesis of styrenic anion exchange resins...

Suzuki and other couplings. This Suzuki coupling has been applied to preparation of 2- and 4-arylpyridines. For a synthesis of styrenes the coupling of arenediazonium salts with potassium vinyltrifluoroborate has been developed. The latter is a. stable and efficient vinylating agent. 

Alkenylzirconium reagents Hydrozirconation of alkynes with Cp ZifHlCl followed by reaction with iodonium salts constitutes a method for synthesis of styrenes and enynes. In the latter case it can be seen that zirconium prefers attachment to the heterosubstituted carbon atom therefore, 1,1-difiinctionalized 1-alkenes are readily prepared, including those pairing Si/Se and Te/Te. ... 

Aral and co-workers [432] reported also a direct route for the preparation of cyclic styrene carbonate from styrene, which avoids the preliminary synthesis and isolation of styrene oxide. A catalyst system consisting of Au/Si02, zinc bromide and tetrabutylammonium bromide (Bu4NBr) was applied to the one-pot synthesis of styrene carbonate from styrene, organic peroxide and CO2. Au/Si02 is active for the epoxidation of styrene, and zinc bromide and Bu4NBr cooperatively catalyse the subsequent CO2 cycloaddition to epoxide. 

Anionic Synthesis of Styrene/IBMA Block Copolymer... 

C-H o-bond activation of hydrocarbons by transition metal complexes is of considerable importance in modern organometallic chemistry and catalytic chemistry by transition-metal complexes [1], because a functional group can be introduced into alkanes and aromatic compounds through C-H o-bond activation. For instance, Fujiwara and Moritani previously reported synthesis of styrene derivatives from benzene and alkene via C-H o-bond activation of benzene by palladium(ll) acetate [2]. Recently, Periana and his collaborators succeeded to activate the C-H o-bond of methane by the platinum(ll) complex in sulfuric acid to synthesize methanol [3], Both are good examples of the reaction including the C-H o-bond activation. 

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