Oxidative coupling of aromatic

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. 

The oxidative coupling of aromatic nuclei activated by alkoxy groups has been explored for the formation of natural products. Thus, laudanosine (VII), Y = NCH3, Z = CH2, has been oxidized [18-22] at a platinum anode in MeCN-TMABF4 to O-methylflavinantine (VIII), and other benzyltetrahydroisoquinolines react similarly on anodic oxidation in good to excellent yield ... 

Oxidative coupling of aromatic nuclei, as discovered by van Helden [8] ... 

The arene substrates are not limited to simple benzene derivatives. A variety of het-eroarenes can also participate in alkene arylations to generate the desired coupling products. Stoichiometric oxidative coupling of aromatic heterocycles such as furan, thiophene, selenophene, A-methylpyrrole, benzofiiran and benzothiophene with a variety of alkenes, including acrylonitrile, styrene and methyl acrylate, have been extensively studied by Fu-jiwara and coworkers [8]. Furan, thiophene, selenophene and A-methylpyrrole are easily alkenylated with alkenes to give 2-alkenylated and 2,5-dialkenylated heterocycles in relatively low yields (3 6%) [8a], while the reactions of benzofuran and benzothiophene with alkenes produced a mixture of 2- and 3-alkenylated products [8b]. 

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. °... 

In 2007, Ueura et al. reported the first effective example for oxidative coupling of aromatic substrates with alkynes through C—H bond cleavage under rhodium catalysis [22]. Thus, benzoic acids 9 and 50 react with alkynes 2 efficiently in the presence of 0.5 mol % of [Cp RhCl2]2 and 2 equiv of Cu(OAc)2 H2O in o-xylene at 100 °C to afford the corresponding isocoumarins 51 as 1 1 coupling products (Scheme 25.26) [5,22]. Five years later, the same reaction was conducted using ruthenium catalysts in place ofRh [23]. 

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. 

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