Arenes vinylation

Grigg, R. Loganathan, V. Sridharan, V., Palladium Catalysed Cascade Alkyne-Arene Vinylation/Alkylation Approach to Polyfused Heterocycles. Tetrahedron Lett. 1996, 37,3399. 

In the presence of TBAF and electron-rich Pd phosphine coirplexes, aryl chlorides react smoothly with arylchlorosilanes and alkenylchlorosilanes to form substituted arenes. The starting (E or Z) geometry of C-C double bond of alkenylchlorosilanes was maintained in the products (eq 34). Trimethox)rvinylsilane was also used in arene vinylation (eq 35), though homocoupling side products were observed with this reagent. ... 

Figure 4.8 onho-Directed oxidative arene vinylation using benzoquinone as the oxidant. 

Figure 4.10 Example of a photochemical rhodium-catalyzed arene vinylation.

Grigg, R., Loganathan, V. and Sridharan, V. (1996) Palladium catalysed cascade alkyne arene vinylation/alkylation approach to polyfused heterocycles. Tetrahedron Lett., 37, 3399-402. 

Based on the proposed mechanism of the stoichiometric alkene arylation, it was anticipated that the same reactions could be achieved using substoichiomelric amounts of palladium salts. In the presence of an oxidant, palladium(O) could be reoxidized to palladium(II), which could then reenter the reaction, thus establishing a catalytic cycle for the arene vinylation reactions. 

Vinyl acetate vinyl arenes vinyl aromatics vinyl esters vinylpyridine... 

FIGURE 13 8 The induced magnetic field of the tt elec trons of (a) an alkene and (b) an arene reinforces the applied field in the regions where vinyl and aryl protons are located... 

This section will describe the Friedel-Crafts alkylation reactions of aromatic hydrocarbons with alkenylchlorosilanes containing short chain alkenyl groups such as allyl and vinyl. The reaction will be discussed in terms of the substituent effect on silicon and the arene rings. 

In 1980 Sonogashira reported a convenient synthesis of ethynylarenes - the Pd-catalyzed cross-coupfing of bromo- or iodoarenes with trimethylsilylacetylene followed by protiodesilylation in basic solution [15]. Prior to this discovery, formation of terminal acetylenes required manipulation of a preformed, two-carbon side chain via methods that include halogenation/dehydrohalogenation of vinyl- and acetylarenes, dehalogenation of /1,/1-dihaloalkenes, and the Vils-meier procedure [ 14]. With the ready availability of trialkylsilylacetylenes, the two-step Sonogashira sequence has become the cornerstone reaction for the construction of virtually all ethynylated arenes used in PAM and PDM synthesis (vide infra). 

Platinum mediated regioselective H-B addition of H-B(cat) to vinyl arenes and alkynes has been realised using the complexes 79 and 80 (Fig. 2.12). The reactions... 

The well-defined copper complexes 94 and 95 (Fig. 2.16) have been used as catalysts for the intermolecular hydroamination of electron-deficient alkenes [Michael acceptors, X=CN, C(=0)Me, C(=0)(0Me)] and vinyl arenes substituted... 

Hydrothiolations (addition of H-SR across the CC multiple bond) of alkynes, electron-deficient aUcenes and electron-deficient vinyl arenes have been catalysed by NHC complexes of Ni and Cu, respectively [Scheme 2.17a-c],... 

Variation in catalyst and ligand can lead to changes in both regio- and enantio-selectivity. For example, the hydroboration of vinyl arenes such as styrene and 6-methoxy-2-vinylnaphthalene can be directed to the internal secondary borane by use of Rh(COD)2BF4 as a catalyst.166 These reactions are enantioselective in the presence of a chiral phosphorus ligand. 

In terms of scope, activated alkenes beyond vinyl arenes, such as nor-bornene, couple effectively to aromatic and ,( >-unsaturated anhydrides, in-... 

Scheme 18 Branch-selective hydroacylation via hydrogen-mediated coupling of vinyl arenes to carboxylic anhydrides...

Carbocycles can also be synthesized by the annulation of alkynes by arene-containing vinylic halides or triflates (Scheme 16). 7 This process involves... 

Another important class of dienes which react readily with ADC compounds are the vinyl arenes. However, the reaction of styrene with ADC compounds does not give simple tetrahydrocinnolines. Styrene and DEAZD give a 1 2 adduct formed by the initial Diels-Alder adduct reacting rapidly in an ene reaction with more DEAZD (Eq. 18).181 Substituted styrenes react... 

Finally, these particles generated in ionic liquids are efficient nanocatalysts for the hydrogenation of arenes, although the best performances were not obtained in biphasic liquid-liquid conditions. The main importance of this system should be seen in terms of product separation and catalyst recycling. An interesting alternative is proposed by Kou and coworkers [107], who described the synthesis of a rhodium colloidal suspension in BMI BF4 in the presence of the ionic copolymer poly[(N-vinyl-2-pyrrolidone)-co-(l-vinyl-3-butylimidazolium chloride)] as protective agent. The authors reported nanoparticles with a mean diameter of ca. 2.9 nm and a TOF of 250 h-1 in the hydrogenation of benzene at 75 °C and under 40 bar H2. An impressive TTO of 20 000 is claimed after five total recycles. 

The vinyl triflate of Komfeld s ketone has been subjected to Heck reactions with methyl acrylate, methyl methacrylate, and methyl 3-(Af-rerf-butoxycarbonyl-lV-methyl)amino-2-methylenepropionate leading to a formal synthesis of lysergic acid [259]. A similar Heck reaction between l-(phenylsulfonyl)indol-5-yl triflate and dehydroalanine methyl ester was described by this research group [260]. Chloropyrazines undergo Heck couplings with both indole and 1-tosylindole, and these reactions are discussed in the pyrazine Chapter [261], Rajeswaran and Srinivasan described an interesting arylation of bromomethyl indole 229 with arenes [262]. Subsequent desulfurization and hydrolysis furnishes 2-arylmethylindoles 230. Bis-indole 231 was also prepared in this study. 

Ito and Katsuki (55) examined the use of chiral bipyridine (bpy) compounds as ligands in the asymmetric cyclopropanation of alkenes. Moderate diastereoselectivities and excellent enantioselectivities were observed in the cyclopropanation of vinyl arenes, Eq. 38. This catalyst system afforded very high ee values of the cis isomer. 

The isomerizations have also proven to be very useful in the synthesis of a series of 1,3-diarylallenes [49-55], even tolerating other functional groups such as aryl chlorides, aryl bromides [56-58] and vinyl bromides [59]. Mixed systems with an alkene on one side and an arene on the other could also be prepared [41, 60], as well as products with two olefinic substituents [61] or bisallenes [62-64],... 

Rhodium-Catalyzed Asymmetric Hydroformylation of Vinyl Arenes. .. 41... 

Abstract This chapter presents the latest achievements reported in the asymmetric hydroformylation of olefins. It focuses on rhodium systems containing diphosphites and phosphine-phosphite ligands, because of their significance in the subject. Particular attention is paid to the mechanistic aspects and the characterization of intermediates in the hydroformylation of vinyl arenes because these are the most important breakthroughs in the area. The chapter also presents the application of this catalytic reaction to vinyl acetate, dihydrofurans and unsaturated nitriles because of its industrial relevance. 

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