Addition of carboxylic acids

Interest in synthetic naphthenic acid has grown as the supply of natural product has fluctuated. Oxidation of naphthene-based hydrocarbons has been studied extensively (35—37), but no commercially viable processes are known. Extensive purification schemes must be employed to maximize naphthene content in the feedstock and remove hydroxy acids and nonacidic by-products from the oxidation product. Free-radical addition of carboxylic acids to olefins (38,39) and addition of unsaturated fatty acids to cycloparaffins (40) have also been studied but have not been commercialized. 

It is appropriate to add here some comments on diazotization in anhydrous carboxylic acids. They may be relevant for the diazotization of heteroaromatic amines carried out in acetic acid/propionic acid mixtures (Sec. 2.2). Extensive studies by Casado et al. (1983, 1984) showed that in nitrosation of secondary amines the nitrosyl ion, nitrosyl acetate, and dinitrogen trioxide are formed, and all three may act as nitrosating agents. The results do not, however, account for the considerable improvement that is claimed in the patent literature (Weaver and Shuttleworth, 1982) to result from the addition of carboxylic acids in the diazotization of heteroaromatic amines. 

Carboxylic esters are produced by the addition of carboxylic acids to alkenes, a reaction that is usually acid catalyzed (by proton or Lewis acids ) and similar in mechanism to 15-5. Since Markovnikov s rule is followed, hard-to-get esters of... 

Addition of carboxylic acids to alkynes Acylation of aldehydes or ketones Bisdecarboxylation of malonic acids Oxidation of arylmethanes with CrOs and AC2O... 

Addition of carboxylic acids or acyl peroxides to alkenes... 

Choi and Sakakura et al. reported that iron(III) triflate, in situ formed from FeCls and triflic acid, efficiently catalyzes the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters. The reaction is applicable to the synthesis of unstable esters, such as acrylates (Scheme 40) [50]. 

Henriksen et al. 1991). A comparable phenomenon is the enhanced dechlorination of tetrachloroethene in anaerobic microcosms by the addition of carboxylic acids including lactate, propionate, butyrate, and crotonate (Gibson and Sewell 1992). 

Examples of the isolation of hydrido(carboxylato) complexes by oxidative addition of carboxylic acid are very rare. Wilkinson [55] examined oxidative addition of fluoro carboxylic acids to Vaska s complex, trans-[lrCl(CO)(PPh3)2]. They isolated colorless hydrido(carboxylato) complexes of stoichiometry, [lrCl(H)(OCORF)(CO)(PPh3)2] (RE = CE3, C2F5), but did not completely succeed in characterizing the products of the oxidative addition. The complex is claimed to be a mixture of four closely similar... 

Acetaldehyde is the product of the Wacker process. At the end of the fifties oxidation of ethene to ethanal replaced the addition of water to acetylene, because the acetylene/coal-based chemistry became obsolete, and the ethene/petrochemistry entered the commercial organic chemicals scene. The acetylene route involved one of the oldest organometallics-mediated catalytic routes started up in the 1920s the catalyst system comprised mercury in sulfuric acid. Coordination of acetylene to mercury(II) activates it toward nucleophilic attack of water, but the reaction is slow and large reactor volumes of this toxic catalyst were needed. An equally slow related catalytic process, the zinc catalysed addition of carboxylic acids to acetylene, is still in use in paint manufacture. 

The addition of carboxylic acids to bicyclo[2.2.1]hepta-2,5-diene has been described by several authors the method described here is a modification of these procedures. Nortricyclanol has been prepared by the hydration of bicyclo[2.2.1]hepta-2,5-diene and the solvolysis of nortricyclyl and bicyclo[2.2.1]hept-2-en-5-yl halides, as well as by the saponification and... 

Acyloxyacrylates are conveniently prepared through the catalyzed addition of carboxylic acids to propiolic esters. Thus, the addition of acetic acid (iron salt) to methyl propiolate yields methyl 3-acetoxyacrylate. Similar additions have been observed with benzoic acid to give the corresponding acrylic esters. 

Addition of Carboxylic Acids Synthesis of Enol Esters... 

Scheme 10.5 Some ruthenium catalysts leading to anti-Markovnikov addition of carboxylic acids to terminal alkynes.

Whereas the Markovnikov addition of carboxylic acids to propargylic alcohols produces P-ketoesters, resulting from intramolecular transesterification [30, 31], the addition to propargylic alcohols in the presence of Ru(methallyl)2(dppe) 1 at 65 °C leads to hydroxylated alk-l-en-l-yl esters via formation of a hydroxy vinylidene intermediate [32, 33]. The stereoselectivities are lo ver than those obtained from non-hydroxylated substrates. These esters, which are protected forms of aldehydes, can easily be cleaved under thermal or acidic conditions to give conjugated enals, corresponding to the formal isomerization products of the starting alcohols (Scheme 10.6). 

In the 1990s, the groups of Hiemstra and Larock independently discovered that Pd(OAc)2 in DMSO serves as an effective catalyst for direct dioxygen-coupled catalytic turnover, and this catalyst system was applied widely to oxidative heterocyclization reactions. Examples include the addition of carboxylic acid, phenol, alcohol, formamide, and sulfonamide nucleophiles to pendant olefins (Eq. 26) [146-149]. 

Fenchone [7787-20-4] containing a small amount of the (-)-isomer [4695-62-9] is prepared by dehydrogenation of (-)-fenchol. (-)-Fenchyl esters are obtained, along with other compounds, by addition of carboxylic acids to a-pinene. Hydrolysis of the esters yields (-)-fenchol. 

Hydrocarboxylation of Alkynes Intramolecular addition of carboxylic acids (weak nucleophiles) to alkynes led to lactones, which were first reported by Schmidbaur et al. in the reaction of acetic add with 3-hexynes to obtain, in addition to enol ester, 3-hexanone. Traces of water were probably present in the solvent to enable the process to be carried out [99]. 

Addition of Carboxylic Acids Hydro-acyloxy-addition... 

Carboxylic esters are produced by the addition of carboxylic acids to olefins, a reaction that is usually acid-catalyzed (by proton or Lewis acids182) and similar in mechanism to 5-4. Since Markovnikov s rule is followed, hard-to-get esters of tertiary alcohols can be prepared from olefins of the form R2C=CHR.183 When a carboxylic acid that contains a double bond in the chain is treated with a strong acid, the addition occurs internally and the product is a y- and/or a 8-lactone, regardless of the original position of the double bond in the chain, since strong acids catalyze double bond shifts (2-2).184 The double bond always migrates to a position favorable for the reaction, whether this has to be toward or away from the carboxyl group. Carboxylic esters have also been prepared by the acyloxymercuration-demercuration of olefins (similar to the procedures mentioned in 5-2 and 5-4).185... 

Interest in synthetic naphthenic acid has grown as the supply of product has fluctuated, Oxidation of naphthene-based hydrocarbons, free-radical addition of carboxylic acids to olefins, and addition of unsatnrated fatty acids to cycloparaflins have been studied but not commercialized. 

The addition of carboxylic acids to olefins proceeds in solution in the presence of 10—4— 10 2 mol dm-3 of H3PW12O40 at 293-413 K with a selectivity of 100% (7). H2S04 is a less active catalyst than H3PW12O40 by a factor of 30-90. Esterification of /j-nitrobenzoic acid with ethanol has been carried out by using H2SO4 catalyst in an industrial process 160). In the presence of H3PW12O40, this reaction takes place with a yield >99% 160). At the end of the reaction, the reaction solution separates into two phases. The upper layer contains ethyl-/ -nitrobenzoate, toluene, and ethanol, and the lower layer consists of a solution of the heteropolyacid in ethanol. Consequently, the catalyst can be readily separated and reused. 

Although a seldom used laboratory method, the addition of carboxylic acids to alkenes provides carboxylic esters. The addition is catalyzed by protic acids or Lewis acids and obeys Markovnikov s rule (equation 273).456-458... 

The intermolecular addition of carboxylic acids to dienes is not very efficient. Conjugated dienes generally form polymeric products 456 whereas nonconjugated dienes tend to give polycyclic products (equation 277J.464 The addition to allenes, on the other hand, is marred by regio- or stereo-isomerism (equation 27S).465... 

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