Carboxylation of aryl halides

Catalyst NiCl2(dppe)2, NiCl2(PPh3)2, NiCl2(PPh3)2 Scheme 66 Nickel-catalyzed carboxylation of aryl halides. 

Electroreductive carboxylation of aryl halides, /J-bromostyrene, and allyl acetates... 

Cobalt(lll)(salen) catalyses the carboxylation of benzyl chlorides and allyl chlorides but not of halobenzenes [246], PdCl2(PPh3)2 catalyses the carboxylation of aryl halides, P-bromostyrene and allyl acetates [247]. 

It is worth noting that the Ullmann-Goldberg condensation of aryl halides with phenols and anilines worked efficiently in the presence of copper in water.50 For example, the coupling of 2-chlorobenzoic acid with 4-chlorophenol (K2C03/pyridine/copper powder) gave 2-(4-chlorophenoxy)carboxylic acid (Eq. 6.23).51 The Cu(I)-catalyzed transformation of 2-bromobenzoic acid into salicylic acid has also been studied in aqueous media (Eq. 6.24).52... 

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

Aromatic carboxylic acids, a,/f-unsaturated carboxylic acids, their esters, amides, aldehydes and ketones, are prepared by the carbonylation of aryl halides and alkenyl halides. Pd, Rh, Fe, Ni and Co catalysts are used under different conditions. Among them, the Pd-catalysed carbonylations proceed conveniently under mild conditions in the presence of bases such as K2CO3 and Et3N. The extremely high toxicity of Ni(CO)4 almost prohibits the use of Ni catalysts in laboratories. The Pd-catalysed carbonylations are summarized in Scheme 3.9 [215], The reaction is explained by the oxidative addition of halides, and insertion of CO to form acylpalladium halides 440. Acids, esters, and amides are formed by the nucleophilic attack of water, alcohols and amines to 440. Transmetallation with hydrides and reductive elimination afford aldehydes 441. Ketones 442 are produced by transmetallation with alkylmetal reagents and reductive elimination. 

The Uppsala team then turned their attention to the development of a fast and efficient procedure that allowed conversion of aryl halides to benzoni-triles and aryl tetrazoles by microwave heating. The aryl bromide 11 was subjected to the optimized reaction conditions, which delivered the bis-tetrazole 15 in a two-step yield of 82% (Scheme 8, Kt = 0.56 nM), demonstrating the potential of the method for medicinal chemistry [61]. The tetrazole functionality is one of the most utilized carboxylic acid bioisosteres. 

In 1972, Screttas10 reported that the reductive lithiation of aryl halides (including fluorobenzene) and (to a lesser extent) alkyl halides was successful even at -50 °C when carried out in THF in the presence of a stoichiometric quantity of naphthalene. Carbonation of the products gave carboxylic acids in high yields.11... 

In the presence of alkyl halides and base, alkyltetracarbonylcobalt complexes are formed with Co2(CO)8 these species [RCo(CO)4] carbonylate a wide range of aryl halides or heterocyclic halides to various products, which depend upon the specific conditions. In the presence of alcohols, carboxylic esters are formed. Under phase transfer conditions and with iodomethane, mixtures of methyl ketone and carboxylic acid formation are realized (equation 207). In the presence of sodium sulfide or NaBH4 in water-Ca(OH)2 (equation 208) good amounts of double carbonylation are realized under very mild conditions412-414. 

Palladium, benzylchlorobis(triphenylphosphine)-, trans-, 67, 86 Palladium-catalyzed aryl-aryl coupling, 66, 70 PALLADIUM-CATALYZED ALLYLIC AMINATION, 67,105 PALLADIUM-CATALYZED CHLOROACETOXYLATION, 67, 105 PALLADIUM-CATALYZED COUPLING OF ACID CHLORIDES WITH ORGANOTIN REAGENTS, 67, 86 PALLADIUM-CATALYZED COUPLING OF ARYL HALIDES, 66, 67 PALLADIUM-CATALYZED syn-ADDITION OF CARBOXYLIC ACIDS,... 

A related reaction is the coupling of two molecules of aryl halide by metallic copper at temperatures above 100° (Ullmann). Activated copper bronze or freshly precipitated copper is used. The order of activity of the aryl halides is I > Br > Cl. Both symmetrically and unsymmetrically substituted biaryls may be prepared in fair yields. An excellent review of the literature to 1945 has been made. Most functional groups do not interfere hydroxyl, carboxyl, amino, and acetamino groups are exceptions. ... 

Alkylation of aryl halides (method 76) and phenols (method 106) is discussed elsewhere as is the application of the Friedel-Crafts reaction to the synthesis of ketones (method 178) and carboxylic acids (method 273)-Nitro and alkoxy groups also have been present on the aromatic nucleus during alkylations. ... 

In addition to halides, leaving groups can be other OR, and so on, even OH. Acid salts, RCOO, are sometimes used as nucleophiles. Good yields of aryl benzoates can be obtained by the treatment of aryl halides with cuprous benzoate in diglyme or xylene at 140-160°C. " Unactivated substrates have been converted to carboxylic esters in low-to-moderate yields under oxidizing condi-... 

Tetracarbonylcobaltate anion, generated under PTC conditions, catalyzes the reaction of aryl halides with excess methyl iodide under a CO atmosphere [122]. The reaction produces aryl methyl ketones and carboxylic acids as the main products. Stoichiometric or catalytic iron pentacarbonyl can also be used for the carbonylation of organohalides under PTC conditions [123-128]. For example, reactions of alkyl and arylalkyl halides with CO in aqueous-organic systems using catalytic amounts of Fe(CO)5 and a PT agent afford alkyl- and arylacetic acids as the main products [127]. 

Suzuki and Stille couplings. For coupling of aryl chlorides with arylboronic acids the catalytic system contains (CyjPjjPdClj, CsF in NMP. co-Arylalkanoic acids are prepared by coupling of aryl halides with carboxylic esters bearing a 9-BBN substituent at the other terminus, and saponification. A biaryl synthesis from two different aryl halides is accomplished with in situ boronate formation which depends on the (dppfjPdClj catalyst. For access to aryl boronates either the coupling of aryl triflates with bis(pinacolato)diboron" or that of aryl iodides with pinacolborane may be employed. 

Goossen LJ, Rodriguez N, Melzer B, Linder C, Deng G, Levy LM (2007) Biaryl synthesis via Pd-catalyzed decarboxylative coupling of aromatic carboxylates with aryl halides. J Am Chem Soc 129 4824-4833... 

This simple protocol for the preparation of carboxylic acids was also successfully applied to carbonylation of alkenyl and aryl bromides under the same reaction conditions [88]. The reaction of aryl halides (including heteroaromatics, e.g., halothiophenes) with methyl acrylate, phenyl vinyl sulfone, cy-clopentene, and dihydrofuran, proceeded smoothly in water using the same PS-PEG-supported catalyst to give the corresponding alkenylated aromatics in high yields [88,89]. 

Heck carbonylation involving the oxidative addition of aryl halides is not applicable to aliphatic halides, since alkyl halides react directly with nucleophiles. Tsuji developed a process of carbonylating allyl carbonates to form carboxylic esters by palladium-catalyzed carbonylation that is applicable to aliphatic substrates [60]. The process probably involves (a) the oxidative addition of allyl carbonates to Pd(0) species to form r/ -allyl palladium species, (b) CO insertion into the allyl-Pd bond to give acylpalladium species, (c) decarboxylation of the carbonate ligand to give alkoxide, and (d) liberation of butenoate esters by combination with the alkoxides as shown in Scheme 1.21. 

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