Oxidative coupling of aromatic compounds

Oxidative coupling of aromatic compounds via the SchoU reaction has been appHed successhiUy to synthesise a polyarylethersulfone (18). High molecular weight polymer was obtained upon treating 4,4 -di(l-naphthoxy)diphenylsulfone and 4,4 -di(l-naphthoxy)ben2ophenone with ferric chloride. Equimolar amounts of the Lewis acid are required and the method is limited to naphthoxy-based monomers and other systems that can undergo the SchoU reaction. 

Palladium-catalyzed oxidative couplings of aromatic compounds with alkenes in air lead to cinnamate products with TONs attaining 280 (Equations (66) and (67)).67,67a,67b... 

Sjoblad, R. D., and Bollag, J.-M. (1981). Oxidative coupling of aromatic compounds by enzymes from soil microorganisms. In Soil Biochemistry, Vol. 5, Paul, E. A., and Ladd, J. N., eds., Marcel Dekker, NewYork, 113-125. 

Van Helden, R. and Verberg, G. (1965) The oxidative coupling of aromatic compounds with palladium salts. Rec. Trav. Chim. Pays-Bas, 84, 1263. 

Tsuji, J. Nagashima, H. Palladium-catalyzed oxidative coupling of aromatic compounds with olefins using tert-butyl perbenzoate as hydrogen acceptor. Tetrahedron 1984, 40, 2699-2702. 

Copper(II) salts and also Fe(lll) salts have been successfully employed in the oxidative coupling of aromatic compounds, mainly for the formation of binaphthyl derivatives. These protocols utilize either stoichiometric or catalytic amounts of copper(ll) and facilitate symmetrical as well as unsymmetrical coupling. 

Oxidation of arylolefins, enolethers, or dienes yields intermolecular homocoupling products in moderate to good yield (see Sect. 13.2.1.4) however, no pronounced diastereoselectivity was observed. This is also due to the fact that the coupling sites do not tolerate substituents that would make up a prostereogenic center. Furthermore, the fairly stable cations of the dimerized radical cation solvolyze stereounselectively. The same holds for the intermolecular coupling of aromatic compounds, in... 

This reaction was first reported by Scholl in 1910. It is a Lewis acid-catalyzed coupling of aromatic compounds while eliminating two of the aryl-bound hydrogens. Therefore, it is generally known as the Scholl reaction,or Scholl condensation. " Occasionally, this reaction is also referred to as the Scholl oxidation. The commonly used Lewis acid is because some other Lewis acids may lead to the formation of... 

The mechanism proposed for the electropolymerization of heterocycles by anodic coupling (Figure 4.3) [15] is analogous to the already known coupling of aromatic compounds [16,17]. The first step consists of the oxidation of the monomer to its radical cation. The second involves the coupling of two radical cations to produce a dihydrodimer dication which leads to a dimer after loss of two protons and rearomatization. Due to the applied potential, the dimer, which is more easily oxidized than the monomer, occurs in its radical form and undergoes a further coupling with a monomeric radical. 

PdCb as catalyst for the oxidative reactions of aromatic compounds has a low reactivity, so usually Pd(OAc)2 is used. For example, as shown in eq. (20.60), the oxidative coupling reaction of phthalic acid diester proceeds to afford a tetra-carboxylic acid derivative [2]. The tetracarboxylic acid is industrially used as a monomer of polyimide. 

Diazo-compounds also result from the oxidative coupling of aromatic amines with bis-pyridinesilver permanganate, a new mild and selective oxidant, and from the two-phase dehydrogenation of hydrazo-compounds, utilising potassium hexacyanoferrate. °... 

Aromatic compounds, 13 108-109 13 680. See also Aromatics acylation of, 12 173-181 amination of, 12 184 arylation of, 12 170-171 Cycloalkylation of, 12 169 in diesel fuel, 12 425 formylation of, 12 178 Friedel-Crafts acylation of, 12 174 Friedel-Crafts alkylation of, 12 164 nitration of, 12 182-183 oxidative coupling of, 19 654 sulfonation of, 12 181 sulfonation reagents for, 23 521-524 Aromatic-containing polymers, sulfonation of, 23 535-536... 

The conversion of aromatic compounds comprises coupling, nuclear and ben-zylic substitution, and in some cases, addition. Homo- and in a more limited scope, heterocoupling is achieved for unsubstituted and substituted aromatic compounds in direct or indirect anodic processes. Chemically, there is a limited variety of expensive oxidation reagents available, but a large scope of transition... 

Block copolymers may also be made by condensation polymerization. Elastomer fibers are produced in a three-step operation. A primary block of a polyether or polyester of a molecular weight of 1000-3000 is prepared, capped with an aromatic diisocyanate, and then expanded with a diamine or dihydroxy compound to a multiblock copolymer of a molecular weight of 20,000. The oxidative coupling of 2,6-disubstituted phenols to PPO is also a condensation polymerization. G. D. Cooper and coworkers report the manufacture of a block copolymer of 2,6-dimethyl-phenol with 2,6-diphenylphenol. In the first step, a homopolymer of diphenylphenol is preformed by copper-amine catalyst oxidation. In the second step, oxidation of dimethylphenol in the presence of the first polymer yields the block copolymer. 

The purpose of present review is to summarize the application of different classes of iodine(III) compounds in carbon-carbon bond forming reactions. The first two sections of the review (Sects. 2 and 3) discuss the oxidative transformations induced by [bis(acyloxy)iodo] arenes, while Sects. 4 through 9 summarize the reactions of iodonium salts and ylides. A number of previous reviews and books on the chemistry of polyvalent iodine discuss the C-C bond forming reactions [1 -10]. Most notable is the 1990 review by Moriarty and Vaid devoted to carbon-carbon bond formation via hypervalent iodine oxidation [1]. In particular, this review covers earlier literature on cationic carbocyclizations, allyla-tion of aromatic compounds, coupling of /1-dicarbonyl compounds, and some other reactions of hypervalent iodine reagents. In the present review the emphasis is placed on the post 1990s literature. 

The use of the above methods does not generally result in the coupling reaction of aromatic compounds, ArX, because of the strong bond of C(sp2)-X in ArX. However, the coupling reaction of a cation radical formed from the single-electron oxidation of aromatics readily occurs. For example, 4-methylquinoline coupled to give bis[2-(4-methylquinolyl)] in 90% yield, by electrolysis [14-19]. Direct irradiation (300 nm) of carbonyl compound (13) in dimethylaniline without a solvent gives rise to ethanolamine (14) as the major product as shown in eq. 2.7 [20]. 

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