A new procedure was developed for synthesis of aromatic and heteroaromatic acids and their derivatives (esters, salts) by carbonylation of the corresponding aryl halides. The acids are selectively formed in a high yield under very mild conditions. Highly active catalytic systems, base-containing alcoholic solutions of cobalt carbonyl modified with epoxides, were used to activate aryl halides.Aromatic acids and their derivatives (esters and salts) are widely used both in preparative organic chemistry and as commercial raw materials to produce pharmaceuticals, plant protecting agents, paint and varnish materials, lubricants, and corrosion inhibitors. In addition, aromatic carboxylic acids are used as the base of modern liquid-crystal materials. Di-and polyaryl carboxylic acids are used in production of polyester fibers and liquid-crystal thermoplastics as well as electroluminophores in development of new equipment.The conventional methods for preparing aromatic acids under industrial and laboratory conditions are different and involve classical organic reactions: alkylation, acylation, oxidation, and cyanidation. The disadvantages of these methods are their low selectivity and high consumption of raw materials. The synthesis is multistep and requires complex process schemes. Many of these methods are environmentally hazardous.Recently, researchers turned attention to an alternative one-step selective procedure for preparing aromatic carboxylic acids: carbonylation of the corresponding aryl halides. Aryl halides are readily available and cheap. However, these compounds, especially the cheapest aryl chlorides, have low reactivity.Originally, [soft] aryl halides (iodides and bromides) were used for this purpose. These compounds can be activated by oxidative addition to complexes of palladium in a low oxidation state [133]. At the same time, alkylaromatic halides are carbonylated under extremely mild conditions in alcohols in the presence of a base and conventional catalyst of oxosynthesis, octacarbonyldicobalt [1, 4, 5].Alkylcobalt carbonyl complexes are formed in situ by the reaction of alkyl halides reactive in nucleophilic substitution (e.g., methyl chloroacetate) with dicobalt octacarbonyl in alcoholic solutions containing a base. These complexes can activate weakly active aryl halides, involving them in carnolylation [6]. In this case, alkyl halides are cocatalysts (activators) of cobalt carbonyl in carbonylation of aryl halides: Co 2 (CO) 8 + A ArHal + CO %%%%%%$ ArCOOR, ROH + B where A and B are cocatalyst and base, respectively.The facts that acceptor substituents accelerate carbonylation of substituted bromobenzenes and oneelectron acceptors (nitrobenzene and anthraquinone) inhibit carbonylation of aryl halides suggests radical anion mechanism of aryl halide activation (S RN 1). The actual carbonylation catalyst is, apparently, the anionic complex [RCo(CO) 3 COOCH 3 ] 3 formed by the nucleophilic attack of the carbon atom of one of the carbonyl groups by the methylate anion. The nucleophilic power of this...
