Copper salts of carboxylic acids

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

Copper(II) acetate and, very probably, other copper salts of carboxylic acids are dimeric (Fig. 11-1). In the acetate hydrate, the two cupric ions have been shown to be linked by four acetate bridges. The... 

Peptide synthesis [1, 1246, before references]. In the presence of triphenylphosphine, copper salts of carboxylic acids undergo condensation with sulfen-amides 33... 

Alternative procedures involve intermediate formation of copper derivatives via decarboxylation of salts of carboxylic acids [123-125] (Figure 10.58). 

The alkali metal salts of carboxylic acids (sodium, potassium, ammonium) are soluble in water but insoluble in non-polar solvents most of the heavy metal salts (iron, silver, copper, etc.) are insoluble in water. 

Decarboxylation (solvent effect). Casini and Cioudman found lhal decarboxylation of 7-nitroindole-2-carboxylic acid by heating with a catalytic amount of the copper salt of the acid proceeded in higher yield and with simpler isolation of product when N,N-dimethylacetamide was used as solvent rather than the conventional quinoline. 

The basic copper salts of benzoic acid and the three toluic acids decompose in nitrobenzene at 200-220° (16 min), the OH group being introduced into the ring next to the carboxyl group, thus giving salicylic and methylsalicylic acids.301... 

Dihydro-2f/-pyran-2-one has been prepared by reductive cycliza-tion of 5-hydroxy-2-pentynoic acid [2-Pentynoic acid, 5-hydroxy-], which is obtained in two steps from acetylene [Ethyne] and ethylene oxide [Oxirane] 3 and by the reaction of dihydropyran [277-Pyran, 3,4-dihydro-] with singlet oxygen [Oxygen, singlet].4,5 2ff-Pyran-2-one has been prepared by pyrolysis of heavy metal salts of coumalic acid [2//-Pyran-5-carboxylic acid, 2-oxo-],8 by pyrolysis of a-pyrone-6-carboxylic acid [211 - Pyran-6-carboxyl ic acid, 2-oxo-] over copper,7 and by pyrolysis of coumalic acid over copper (66-70% yield).8... 

The decarboxylation of aromatic acids is most often carried out by heating with copper and quinoline. However, two other methods can be used with certain substrates. In one method, the salt of the acid (ArCOO ) is heated, and in the other the carboxylic acid is heated with a strong acid, often sulfuric. The latter method is accelerated by the presence of electron-donating groups in ortho and para positions and by the steric effect of groups in the ortho positions in benzene systems it is... 

Protection2 and activation1 of carboxylic acids. Carboxylic acids react with 1 in the presence of a 2-chloropyridinium salt, proton sponge, and DMAP to form amides (2). These amides are stable to acids and bases but deprotection is possible with oxidative hydrolysis with ceric ammonium nitrate (CAN). If the oxidation is carried out in the presence of an amine, an amide is obtained in 70-95% yield. For this purpose, the combination of copper(II) oxide and ceric pyridinium chloride is far superior to CAN.4 No racemization was observed in the benzoylation of an a-amino ester. 

Alcohol 6 is prepared by a copper-catalyzed reaction of (R)-benzylglycidyl ether with vinylmagnesium bromide. The first step here is a Williamson ether synthesis. The free alcohol 6 reacts with sodium hydride to a sodium alkoxide, which is treated with the sodium salt of bromoacetic acid. The acid is also converted into the sodium salt to avoid the formation of an ester as side product. After the reaction carboxylic acid 20 is released in 93 % yield by acidification with aqueous 10 % HC1 solution. 

The principle has been applied to the preparation of aromatic compounds from the carboxylic acid copper salts.6 The disappearance of the blue colour of the copper salt indicates the completion of the reaction. Ethylene diamine is produced from the copper salt of glycine —... 

The decarboxylation of copper perfluorobenzoate in quinoline gives (CuQF5) . The catalytic action of copper or copper salts on decarboxylation reactions of carboxylic acids presumably involves organo intermediates. 

It is interesting to note that ferric salts of organic acids such as citric, tartaric, etc., are not as a rule ferric salts in the ordinary acceptation of the term. The iron has entered into the electro-negative radicle in an analogous manner to copper in the organic copper derivatives.4 In ferric oxalate and in the ferricyanides, which latter do not contain hydroxylic or carboxylic groups, the iron is similarly in the negative radicle. 

Hydrolysis of acid chlorides, acid anhydrides, esters and carboxamides leads to the carboxylic acid, although these compounds are often derived from a carboxylic acid group in the first place (Scheme 5.5). Nitriles are usually derived from amines via diazotization and reaction with copper(I) cyanide (see Chapter 8) and so the hydrolysis of a nitrile group is of more value. In all cases, alkaline hydrolysis gives the salt of the acid, from which the free acid is obtained by addition of mineral acid. 

A nice complement to the Haller-Bauer reaction (Section II.B) is the decarbonylation of aldehydes with (Ph3P)3RhCl (Wilkinson s catalyst) A recent example comes from the work of Baldwin and Barden and is shown in Figure 5. Interestingly, partial optical resolution was achieved in this synthesis by use of an optically active copper catalyst for the preparation of the labeled phenylcyclopropane carboxylic acid. The resolution to optical purity was then accomplished by recrystallization of the quinine salt of the acid. 

Racemic cis-raonoesters of cyc1opentene-3,5-d1ol have been previously prepared by the selective acylation of the raeso-diol and the copper-mediated addition of carboxylic acid salts to cyclopentadiene monoepoxide. Optically active monoacetates can be accessed by enzymatic hydrolysis of the corresponding diester. The present method offers four principal advantages over the earlier reports (1) it is operationally simple, (2) it requires a much shorter reaction time, (3) it gives better yields, and (4) it has widespread applicability, since reactants other than carboxylic acids may be employed with equally good results. 

Several interesting variations on the above radical chemistry have been described recently. One such system is copper salt catalyzed alkane oxidation by dioxygen in the presence of an aldehyde [17]. The proposed mechanism involves the initial autoxidation of the aldehyde to the corresponding peracid, which is the real oxidant for the Cu"-mediated oxidation of the alkane (eqs. (3)-(5)). The ratio of alkane oxidized to aldehyde converted is relatively low because much of the peracid formed reacts with the aldehyde to form two molecules of carboxylic acid. 

In the late 1980s, the group of Maumy described the first mild method for the EDP [23]. Prochiral phenylalkylmalonic acids 42 were decarboxylated at 60°C in acetonitrile in the presence of a combination of cinchonidine 26 and copper (I) chloride. Low enantiomeric excesses of carboxylic acids 44 were obtained using more than 1 equiv of cinchonidine 26 (due to the acidic character of the product) with a substoichiometric amount of the copper salt (Scheme 7.19). EDP, performed with racemic hemimalonates 45 using catalytic amounts of the copper-cinchonidine system (20 and 40 mol%, respectively), afforded comparative levels of enantioselec-tivity (Scheme 7.20). 

Octel Chemicals have patented a process to decompose the diazonium at nearly room temperature using a copper salt of hydroxy carboxylic acid, allowing them to use conventional glass lined reactors, but with poor productivity and problems of copper effluent in aqueous. 

The decarboxylation of CuOCOC6F5 in quinoline forms CuC6F5, and indeed organo coppers appear generally to be intermediates in the decarboxylation of carboxylic acids, and their catalytic action explains the long-known effectiveness of copper metal or copper salts in such reactions. 

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