Aryl carboxylic acids

When an alkyl aryl ketone is heated with yellow ammonium polysulphide solution at an elevated temperature, an aryl substituted aliphatic acid amide is foimed the product actually isolated is the amide of the ci-aryl carboxylic acid together with a smaller amount of the corresponding ammonium salt of the oarboxylio acid. Thus acetophenone affords phenylacetamide (50 per cent.) and ammonium phenylacetate (13 per cent.) ... 

Band 4, 5-9411 (1683 cm. ). Aryl carboxylic acid C=0 stretching vibration (Table IV). 

Suitable starting materials for the Kolbe electrolytic synthesis are aliphatic carboxylic acids that are not branched in a-position. With aryl carboxylic acids the reaction is not successful. Many functional groups are tolerated. The generation of the desired radical species is favored by a high concentration of the carboxylate salt as well as a high current density. Product distribution is further dependend on the anodic material, platinum is often used, as well as the solvent, the temperature and the pH of the solution." ... 

Dehydration (cf., 6, 648). A reagent (1), prepared in situ from (C6H5),PO and Tf20 in the molar ratio 2 1, effects dehydration, usually at 25°, of amides or oximes to nitriles in >90% yield. It also effects condensation of acids and amines to form amides. The reaction of an aryl carboxylic acid with an o-phenylenediamine promoted by 1 provides 2-arylbenzimidazoles in >80% yield (equation I). If the... 

Aryl methyl ketones have been obtained [4, 5] by a modification of the cobalt-catalysed procedure for the synthesis of aryl carboxylic acids (8.3.1). The cobalt tetracarbonyl anion is converted initially by iodomethane into the methyltetra-carbonyl cobalt complex, which reacts with the haloarene (Scheme 8.13). Carboxylic acids are generally obtained as by-products of the reaction and, in several cases, it is the carboxylic acid which predominates. Unlike the carbonylation of haloarenes to produce exclusively the carboxylic acids [6, 7], the reaction does not need photoinitiation. Replacement of the iodomethane with benzyl bromide leads to aryl benzyl ketones in low yield, e.g. 1-bromonaphthalene produces the benzyl ketone (15%), together with the 1-naphthoic acid (5%), phenylacetic acid (15%), 1,2-diphenylethane (15%), dibenzyl ketone (1%), and 56% unchanged starting material [4,5]. a-Bromomethyl ketones dimerize in the presence of cobalt octacarbonyl and... 

It has been proposed that in this reaction CO2 reacts as an electrophile with [ArPd (PPh3)2] formed by reduction of the aryl-palladium(II) [102]. Aryl chlorides react too slowly with Pd° to enable an efficient carboxylation reaction. On the other hand aryl triflate and aryl bromide have similar reactivity. The synthesis of aryl carboxylic acids can then be obtained from phenols via the formation of the corresponding aryltriflate (Eq. 15) [29, 30] ... 

Oxidation of an alkylated benzene (making an aryl carboxylic acid) is a method of converting an ortho-para activator into a meta director. The reduction of a nitro group to make an aryl amine is a way of changing a meta director into an ortho-para activator. 

Tetrakis-/i-(carboxylato)-dimolybdenum(II) complexes have been obtained by only one general route, namely by the direct interaction of carboxylic acids with molybdenum hexacarbonyl.8 This reaction requires elevated reaction temperatures and prolonged reaction times. These same compounds are obtained in comparable or better yields by the brief reaction of tetrachloro- or tetrabromotetrakis(tributylphosphine)dimolybdenum(II) with alkyl- or aryl-carboxylic acids in refluxing benzene. The bis-/i-(arylcarboxylato) complexes... 

ProMem 10.35 Which isomer of the arene C,oH,4 resists vigorous oxidation to an aryl carboxylic acid ... 

Diaryl ketones.2 In the presence of this complex (1 equivalent) S-(2-pyridyl) aryl thioates (1 equivalent), prepared from aryl carboxylic acids, undergo reductive homocoupling to diaryl ketones (equation I). 

ArenecarboxyHc acids.1 Aryl diazonium tetrafluoroborates react with carbon monoxide in the presence of catalytic amounts of Pd(OAc)2 to give aryl carboxylic acids in 70-85% yield. 

The surprising occurrence of photoionization in aryl carboxylic acids may be explained by the transfer of excitation energy from the ring system to the carboxyl group to give an intermediate with charge separation at the side-chain terminus—e.g.,... 

The mercapto group of 9-mercapto-4//-pyrido[ 1,2-a]pyrimidin-4-ones 513 was alkylated with (het)aralkyl bromides and chlorides in the presence of potassium carbonate in dimethylformamide at ambient temperature for several hours. It also was acylated with carboxyl chlorides in the presence of potassium carbonate in acetone at room temperature or with mixed anhydride, prepared from aryl carboxylic acid and ethyl chloroformate,... 

A highly enantioselective alkylation of 3,5-diaryloxazolidin-2,4-diones 70 with N-spiro chiral quaternary ammonium bromide (S,S)-69 was achieved under mild phase-transfer conditions. With this methodology in hand, a wide range of tertiary a-hydroxy-a-aryl carboxylic acid derivatives may easily be obtained in good yields and high enantiomeric excesses (Scheme 5.34) [35]. 

Of particular interest to combinatorial chemistry is the use of immobilised functionalised boronic acid templates which are capable of further transformations [20]. For instance, an aryl carboxylic acid 50 can be converted into the corresponding amide 51 (Scheme 12), whilst still being attached to the resin. Benzyl amine and butylamine were coupled efficiently to afford (after cleavage) the corresponding amides 52 in high yield (Scheme 12). 

Except for some activated acids, for example aryl carboxylic acids, decarboxylation of free carboxylic acids is often difficult [17]. Under the reaction conditions used for of the deuteration in Scheme 6 (i.e. Pd/C catalyst, in deuterium oxide at 250 C/4-5 MPa), decarboxylation was observed - a carboxyl group is exchanged with a D atom, accompanied by H-D exchange reaction on all carbons [18]. 

Table 32 Yields of 784 and 785 for the Pd(n)—Cu(ii) coupling of aryl carboxylic acids with styrene...

Phenvalera te)] (chlorinated aryl carboxylic acid ester) analogue of Pyrethrin I sensitive TTX-resistant) activator (persistent open state depolarization, block, paralysis) [insecticide, proconvulsant, toxic]... 

Reaction of Ceo with [NO][Bp4] in the presence of aryl carboxylic acids (ArC02H) in H2O yields a mixture of C6o(02CAr)x(OH)j, isomers, which were warmed with aqueous NaOH to yield the water-soluble polyhydroxylated derivatives C6o(OH) n < 20). Similar products (n < 15) have been prepared by the direct reaction of Ceo with a mixture of concentrated nitric and sulfuric acids. The polymethoxylated derivatives C6o(OMe) (n < 26) have been prepared from polychlorinated Ceo (Section 6.2.2). 

One limitation is that this re=action cannot be used for rearrangement of amides of aryl carboxylic acids because anilines are subject to further oxidation. ... 

Several polynuclear aromatic hydrocarbons may be synthesized by procedures involving decarboxylation. The dry distillation of 3-phe-nanthrylacetic acid and powdered soda lime furnishes the best method of synthesis of 3-methylphenanthrene (84%). Heating aryl carboxylic acids with copper powder or copper oxide in quinoline or quinaldine is also an effective method of decarboxylation. ... 

In the presence of a catalytic amount of the chiral titanium reagent (8) prepared from titanium tetraisopropoxide and the (/ )-1,4-diol, kinetic resolution of 5 -(2-pyridyl) thioesters of a-aryl carboxylic acids is achieved with high relative rate of both the enantiomers to give the (f )-isopropyl esters with high optical purity (eq 17). ... 

In addition to aryl carboxylic acids, including profens (2-aryl propionic acid NS AIDs) (see Fig. 9.36) [393,398], the terguride-based CSP has shown the potential to re.solve the enantiomers of 2-aryloxypropionic acids [394] and of A-dansyl, A-3,5-dinitrobenzoyl, A-benzoyl, A-P-naphthoyl amino acid derivatives [395]. 

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