Copper, reaction with aryl carboxylic acids

Yes, many functionalized alkynes such as ynamides and ynol ethers are well tolerated in several metal-catalyzed vinyl ester syntheses [139, 140] Decarboxylation is a common side reaction with this chemistry however, a copper-catalyzed approach has minimized this secondary process and generated good to excellent yields of the vinyl esters with electron-rich aryl carboxylic acids [130]... 

Even though the Jourdan-Ullmann condensation has been known for more than a century, the mechanism is still not quite clear. On the one hand, the reaction may proceed via a free-radical mechanism, pertaining to the reductive dehalogenation of aryl halides and the acceleration of the reaction rate by ultraviolet irradiation, as outlined in Scheme 1. On the other hand, the reaction may involve halonium and proceed as a simple aromatic nucleophilic substitution, as displayed in Scheme 2. However, for the reaction of 6>-halobenzoic acid, it is believed that the copper ion coordinates with both carboxyl and... 

Alternatively, boronic acids react under the influence of Cu-catalysis with electrophilic iV-thioimides under mild conditions and in the absence of base (Eqn. 1-7). Various copper carboxylates can be used (e.g., CuMeSal, CuTC, and CuOAc) but not salts such as CuCl, CuCN, or CU2O. A presumed Cu(I)/Cu(III) cycle is put forth, where the thioimide is oxidatively added to the Cu(I) catalyst, and the RB(0H)2 supplies the R group on the metal (with loss of imide-B(OH)2) prior to reductive elimination. Several biaryl thioethers were made in this way (e.g., 85,86) in THF (or dioxane), along with aryl alkenyl derivative 87. All bases examined (K2CO3, NaOH, TBAF, pyridine, EtsN) inhibited the reaction. 

Scheme 4.26 shows the development of two general reactions based on copper(I) thiophene-2-carboxylate (CuTC) or Cu(OAc)2 for the formal arylation of imtnes with arylboronic acids [62]. The O-acetyl or O-pentafluorophenyl oximes react with a wide range of electron-rich, electron-poor and electron-neutral boronic acids, and even ortho-substituted substrates react well. The mechanism is proposed to proceed, as shown in Scheme 4.27, via an initial oxidative addition of the copper(I) species, either CuTC or through reduction of Cu(OAc)2 by the boronic acid, to the ketoxime O-carboxylate. This is followed by transmetallation and reductive elimination to generate the final product and regenerate the catalytically active copper(I) species. 

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