Aryl chlorides, decarboxylative couplings

GooBen LJ, Zimmermann B, Knauber T (2008) Palladium/copper-catalyzed decarboxylative cross-coupling of aryl chlorides with potassium carboxylates. Angew Chem Int Ed 47 7103-7106... 

Aryl chlorides are widely used for C-C bond creation under Pd(0)-Pd(II) catalytic cycle conditions [62], As a consequence, use of cheaper ArCl in benzoic acid arylation should also be possible if appropriate ligands are used and catalytic cycle for the arylation is changed from Pd(II)-Pd(IV) to a Pd(0)-Pd(II) couple. The method involves use of catalytic palladium acetate in combination with butyl-di-1-adamantylphosphine ligand, cesium carbonate base, and an aryl chloride coupling partner [61]. Benzoic acids of any electronic properties are reactive (Scheme 15). Electron-poor benzoic acids react well, and it is possible to couple them with both electron-poor and electron-rich aryl chlorides. Both electron-poor and electron-rich aryl chlorides can be coupled with electron-rich benzoic acids. However, the combination of an electron-rich aryl chloride with an electron-rich benzoic acid is occasionally problematic due to product decarboxylation or aryl halide hydrodehalogenation. The nitro group is compatible with the reaction conditions, as is the ester group. 

The palladium-catalyzed decarboxylative coupling of potassium pentafluoroben-zoate with aryl chlorides, bromides and triflates was shown to be a useful method for the synthesis of polyfluorobiaryls from readily accessible polyfluorobenzoate salts. For instance, 2- and 3-chlorothiophens 218, 219 reacted with potassium pentafluorobenzoate to produce pentafluorophenyl derivatives 210 and 220. The reaction proceeded in refluxed diglyme in the presence palladium acetate(ll) [111],... 

A complex consisting of Cu 1.10-phenanthroline [which mediates decarboxylation of arylcarboxylic acids with formation of aryl Cu species] and Pd(acac)2 [for coupling] was made and used to catalyse the decarboxylative cross-coupling of the Cu species with aryl halides. This bimetallic system allows direct coupling of a variety of aryl, heteroaryl or vinyl carboxylic acids with aryl or heteroaryl bromides, chlorides or iodides at 160° in N methylpyrrolidine in the presence of K2CO3. [Goossen et al. JAm Chem Soc 129 4824 2007]. 

Shang R, Xu Q, JiangYY, Wang Y, Liu L (2010) Pd-catalyzed decarboxylative cross coupling of potassium polyfluorobenzoates with aryl bromides, chlorides, and triflates. Org Lett... 

---