Oxidative coupling of aromatic substrates

Nu = external or intmial nucleophilic group, including electron-rich aromatics 

Under similar conditions, the phenanthro-fused thiazoles 302, isoxazoles 304 (X = O, n = 0) and pyrimidines 304 (X = N, n = 1) can be prepared by oxidative coupling of the respective phenol ethers 301 and 303 

Additional examples of intramolecular oxidative coupling of phenolic ethers include the oxidative biaryl coupling of various N-substituted 1-benzyltetrahydroisoquinolines 313 to the corresponding aporphines 314 [374], the oxidative cyclization of 3,4-dimethoxyphenyl 3,4-dimethoxyphenylacetate (315) leading to the seven-membered lactone 316 [375] and the conversion of phenol ether derivatives 317 into the products of 

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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]. 

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