Carboxylic acids, conjugated acetate

The chloroacetoxylation is a quite general reaction and works well with a number of conjugated dienes. Some additional examples are given in Scheme 6 and in equations 15 and 16. The reaction is highly syn stereoselective for a number of cyclic dienes tried. Also, for acyclic dienes the reaction leads to a 1,4 syn addition and the reaction takes place with good stereospecificity (94 -96% syn). Thus (Zi,.E)-dienes give the R R isomer whereas (E,Z)-dienes produce the R S isomer (equations 15 and 16). The reaction has also been extended to include other carboxylic acids than acetic acid (chloroacyloxylation)33d. 

Vinyl carboxylic acids (conjugated acids) were shown to react with NBS and lithium acetate in aqueous acetonitrile, to give the corresponding vinyl bromide (C=C COOH C=C Br), using microwave irradiation." A similar reaction was reported using Na2Mo04, KBr and aqueous hydrogen peroxide... 

The CD fragment 1s synthesized starting with resolved bicyclic acid 129. Sequential catalytic hydrogenation and reduction with sodium borohydride leads to the reduced hydroxy acid 1. The carboxylic acid function is then converted to the methyl ketone by treatment with methyl-lithium and the alcohol is converted to the mesylate. Elimination of the latter group with base leads to the conjugated olefin 133. Catalytic reduction followed by equilibration of the ketone in base leads to the saturated methyl ketone 134. Treatment of that intermediate with peracid leads to scission of the ketone by Bayer Villiger reaction to afford acetate 135. The t-butyl protecting... 

The enolization constants of carboxylic acids to form enediols are generally still lower than those of ketones. The pAE of acetic acid is about 20.35 Due to the relatively high acidity of 1,1-enediols, the enol content of carboxylate anions is somewhat higher. When the carboxylate is attached to cyclopenta-dienyl, a strong mesomeric electron acceptor, the conjugate acid of the enol, fulvene-l,l-diol, becomes a strong acid, pAa = 1.3, and the pAE of the enol anion is reduced to 5.0 (Almstead JIK and Wirz J, Unpublished data).36,37... 

The IUPAC rules name esters as alkyl alkanoates. That is, the portion of the ester derived from the alcohol is named as an alkyl group. The portion of the ester that is derived from the carboxylic acid is named as the conjugate base of that acid. It is easy to distinguish these parts. The half derived from the carboxylic acid has the carbonyl group. Pentyl ethanoate, or pentyl acetate, is one ester used as artificial banana flavoring. Figure 11.51 shows three ester nomenclature examples. 

Three-component additions, comprising two conjugated diene molecules and a nucleophile, can be catalyzed by palladium salts, such as palladium acetate. The major products are 1-substituted 2,7-octadienes, along with minor amounts of 3-substituted 1,7-octadienes (equation 65). Water, alcohols, phenols, carboxylic acids, and amines are some of the nucleophiles that have been used in this reaction. 

Because the pK values of many carboxylic acids are 5, bases that have conjugate acids with pKg values higher than 5 are strong enough to deprotonate them. Thus, acetic acid (pATa = 4.8) and benzoic acid (pA a = 4.2) can be deprotonated with NaOH and NaHC03, as. shown in the following equations. 

Dipole moment studies of the conformations of arylimidazoles have shown that the aryl ring is not always coplanar with the heterocyclic C-NMR spectroscopy of phenylimidazoles has been studied. In mixed acids 1-phenylimidazole is nitrated as the conjugate acid to give mainly the p-nitrophenyl product with nitric acid in acetic anhydride only the nitrate salt forms. With 4-(p-alkoxyphenyl) imidazoles much of the nitration occurs ortho to the alkoxy group" the alkoxynitroaryl substituents are readily oxidized to carboxyl by alkaline permanganate. ... 

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