Arene carboxylates

There are several 2-ketoglutarate anaerobic oxidoreductases, for example, in Thauera aro-matica (Dorner and Boll 2002) and Azoarcus evansii (Ebenau-Jehle et al. 2003). Their role in the metabolism of arene carboxylates is discussed in Chapter 8, Part 3. 

The reductive transformation of arene carboxylates to the corresponding aldehydes under aerobic conditions has already been noted. In addition, aromatic aldehydes may undergo both reductive and oxidative reactions, with the possibility of decarboxylation of the carboxylic acid formed ... 

In the presence of palladium(II) and silver(I) salts, arene carboxylates could be converted to aryl palladium species, which were engaged in Heck coupling reactions.90 Since the more electrophilic palladium trifluoroacetate proved to be the bestcatalyst, decarboxylation probably occurred by aromatic electrophilic substitution... 

The photochemistry of carboxylic acid derivatives has been summarized by Coyle [20]. For arene carboxylic acid esters it has been shown that [2+2] cycloaddition competes with hydrogen abstraction by the excited ester from an allylic position of the alkene. The addition of methyl benzoate 17 to... 

Solvent extraction of Fe(III) with calix(6)arene carboxylate derivative followed by spectrophotometric determination with thiocyanate was examined [1]. The developed method was recommended for determination of Fe(III) in samples containing Al, Mn(II), Mo(VI) and V(V). The extraction of Fe(III) with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester followed by the determination with thiocyanate was employed to determine Fe in pharmaceuticals, metal and ores [2]. Solvent extraction separation of iron(III) with Cyanex 302 prior to the detection as the thiocyanate complex was applied to determine Fe(III) in multicomponent mixtures and ores, alloys and pharmaceuticals [3]. 

Myers AG, Tanaka D, Mannion MR (2002) Development of a decarboxylative palladation reaction and its use in a Heck-type olefination of arene carboxylates. J Am Chem Soc 124 11250-11251... 

Tanaka D, Romeril ASP, Myers AG (2005) On the mechanism of the palladium(II)-catalyzed decarboxylative olefination of arene carboxylic acids. Crystallographic characterization of non-phosphine palladium(II) intermediates and observation of their stepwise transformation in Heck-like processes. J Am Chem Soc 127 10323-10333... 

The phthalimide functional group has absorption and ET properties which make it very attractive in terms of PET processes in which it is the oxidizing species. The application of phthalimide derivatives in carbon-carbon bond forming processes with electron-donating groups such as ethers, thioethers, amines, arenes, carboxylates, etc., has been reviewed. A PET decarboxylation-cycliz-ation sequence has been used for the synthesis of medium-sized (8-16) heterocyclic ring systems (15) from AT-phthaloylanthranilic amides coupled to ca-aminoacids (14). The same PET protocol has been used to convert di-, tri-, and tetrapeptides into cyclopeptides with a minimum of protection and activation... 

Cyanation of aryl hahdes, boronates, boronic acids, arene carboxylic acids, and (hetero)arene C—H bonds using nonmetaUic cyano-group sources 12AG(E)11948. 

SCHEME 22.9 Pd(ll)-catalyzed decarboxylative aUylation of arene carboxylates with allylic haUdes. 

Rh-Catalyzed Reactions Zhao and coworkers have shown that the reaction of ortho-substituted arene carboxylic acids with electron-deficient olefins in the presence of ahydrorhodium(I) complex as the catalyst gave the Mizoroki-Heck products (8) and the conjugate addition products (9) with high selectivity (Scheme 22.18a) [13, 26]. The selectivity depends on the content of water in the reaction mixture higher water content favored the hydrolysis of the enolato intermediate 10, while lower water content favored P-H elimination. This reaction works only for ortho-suhstituted arene carboxylic acids and with electron-deficient olefins (Scheme 22.18h). 

An unexpected Pd-mediated conpling reaction of arene carboxylic acids with nitroethane via a combination of decarboxylation and dehydrogenation has been reported by Su and coworkers [42]. This method provides exclnsively ( )- 3-nitrostyrenes. Su et al. varied the reaction conditions... 

Alternatively, biaryls (including sterically hindered biaryls) can be synthesized by the reaction of arene carboxylic acids with diaryhodonium salts by means of a PdCl /DEPhos catalytic system at 150°C in the presence of Ag COj [58]. 

Wang, J., Cui, Z., Zhang, Y, Li, H., Wu, L.-M., Liu, Z. (2011). Pd(II)-catalyzed decarboxylative allylation and Heck-coupling of arene carboxylates with allylic halides and esters. Organic and Biomolecular Chemistry, 9, 663-666. 

Various enzymes are known to catalyze arene carboxylation or decarboxylation in nature [41]. The first report [42] of a preparatively useful biocatalytic arene carboxylation was the para-carboxylation of phenol using the enzyme phenyl phosphate carboxylase. As the name imphes, this requires the phenol to be phosphorylated prior to reaction. Subsequently, phenol para-carboxylation without prior phosphorylation was demonstrated using enzymes such as 4-hydroxybenzoate decarboxylase [43-45] and 3,4-dihydroxybenzoate decarboxylase [46, 47] (Scheme 32.10). Although the natural function of these latter enzymes is to catalyze catalyze reactions in either direction, dependent on the reaction conditions. 

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