Chemoselectivity of cobalt-catalysed carbonylation—A reliable platform for the synthesis of fluorinated benzoic acids

The cobalt-catalysed methoxycarbonylation of polysubstituted bromo,fluoro- and chloro,fluorobenzenes and 1,2,4-trichlorobenzene with emphasis on the chemo- and regio-selectivity of the reaction is described. The structures of isolated products of 1,4-dichloro-2-fluorobenzene carbonylation were determined by single-crystal X-ray diffraction. The fact that the fluorine substituents in the studied compounds remain intact indicates in favor of the anion-radical activation of aryl halides by a cobalt catalyst. For the first time, a universal method of preparation of the various fluorobenzoic acid derivatives from available raw materials with a good yield has been elaborated.

Graphical abstractThe high selectivity of cobalt-catalysed carbonylation of mixed aryl halides (bromo,fluoro- and chloro,fluorobenzenes) and 1,2,4-trichlorobenzene is demonstrated and explained by anion-radical mechanism of aryl halides activation by modified cobalt carbonyl complex. It allows using this effective procedure as a universal method for synthesis of fluorinated benzoic acids.Figure optionsDownload full-size imageDownload as PowerPoint slide