Esters reaction with carboxylic acids

In the previous review (91YGK205, 99H1157), we reported that l-hydroxy-4-nitroindole forms active ester derivatives by reaction with carboxylic acids, which can be applied to acylation of various nucleophiles. To expand the scope of the reaction and obtain novel fungicidal compounds, an attempt has been made to prepare derivatives of wasabi phytoalexin 109 (98P1959). 

Reactions with Carboxylic Acid Esters Alkyl nitrones can be metallized upon treatment with phenyl lithium in ether solution. The Li-derivatives react with carboxylic acid esters to give 3-oxo nitrones (305)- the analogs of 3-diketones and j3-keto esters (545). With the help of the 13C NMR method it has been found that 3-oxo nitrones (305) exist as an equilibrium mixture... 

Chemical Properties. Hydrogenation of menthols yields / -menthane oxidation with chromic acid or catalytic dehydrogenation yields menthones. Dehydration under mild conditions yields 3-/ -menthene as the main product. Reaction with carboxylic acids or their derivatives yields menthyl esters, which are used mainly as aroma substances and in pharmaceutical preparations and formulations. The esterification of menthols with benzoic acid is used on an industrial scale in the resolution of racemic menthol. 

Cinnamic alcohol can be dehydrogenated to give cinnamaldehyde and oxidized to give cinnamic acid. Hydrogenation yields 3-phenylpropanol and/or 3-cyclo-hexylpropanol. Reaction with carboxylic acids or carboxylic acid derivatives results in the formation of cinnamyl esters, some of which are used as fragrance materials. 

Chiral 2,2-disubstituted cyclobutanones have been obtained by asymmetric rearrangement of chiral sulfinyl- 177,178 and sulfanylcyclopropanes.179 Using readily available cyclopropyl 4-tolyl (/ )-sulfoxide (l),180 the requisite sulfinylcyclopropanes 3 and 3 were obtained by a sequence of lithiation, reaction with carboxylic acid esters and stereoselective addition of Grignard reagents to the ketones 2 thus formed.178 The corresponding sulfanylcyclopropanes 4 and 4 resulted from a sequence of protection, reduction and deprotection.179... 

Trimethylsilyl ethers and esters.i The reaction of alcohols and allyltrimethyl-silane in acetonitrile with TsOH as catalyst (70 80°, 1 3 hours) results in trimethyl-silyl ethers in 85-95% yield with elimination of propene. The same reaction with carboxylic acids results in trimclhylsilyl esters. Phenols do not undergo this reaction. 

Benzohydroxamic acid dioxouranium complexes, 507 metal complexes, 506, 507 as metal precipitant, 506 Benzohydroxamic acid, iV-methyl-metal complexes, 506 Benzohydroxamic acid, N-phenyl-metal complexes, 507 reactions with carboxylic acids, 507 as metal precipitant, 506 titanium complexes, 506 Benzohydroxamic acid, A -(o-tolyl)-as metal precipitant, 506 Benzohydroxamic acid, N-wi-tolyl-p-methoxy-metal complexes, 506 Benzoic acid, dihydroxy-beryllium(II) complexes, 481 Benzoic acid, o-mercapto-esters... 

Amines undergo reactions with carboxylic acids comparable to the formation of esters from alcohols. The product is known as an amide. 

In practice, the reaction with carboxylic acids, DCC and amines leads to amides without problems, while the addition of approximately 5 mol-% DMAP is crucial for the efficient formation of esters. 

The single most valuable application of diazomethane is its reaction with carboxylic acids to provide the equivalent methyl ester, under very mild conditions. This and other reactions of the reagent have been well reviewed. ... 

Cyanuric chloride has been used for the preparation of acyl chlorides, amides, and peptides. Conversion of cyanuric chloride into 2-chloro-4,6-dimethoxy-l,3,5-triazine (CDMT, 6) leads to a reagent that upon reaction with carboxylic acids produces the highly reactive 2-acyloxy-4,6-dimethoxy-l,3,5-triazines.P l The resulting active ester is a powerful acylating agent for alcohols and amines. The activation is performed in presence of a base, preferentially NMM, which leads to intermediate formation of 4-(4,6-dimethoxy-l,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM, 7)P l (Scheme 5). This addition product is readily prepared from the commercially available CDMT (6) and NMM in THF and can be stored as solid compound in the cold.P P l It offers the advantage that it can be used in a one-... 

It should finally be pointed out that trimethylsilyl ethers can also be transformed directly into other functionalities. Oxidation with NBS leads to ketones and aldehydes, treatment with LiAllWAlCb results in deoxygenation of the alcohol, reaction with carboxylic acid anhydrides in the presence of BF3-OEt2 produces esters and on treatment with PhsP Brj acid bromides are foimed directly from TMS esters. ss... 

Alkyl-, aryl-, and hetaryl aldehydes react with o-aminothiophenol in DMSO to give the corresponding 2-substituted benzothiazoles (371) (Equation (76)) <90DP243>. Similar reactions with carboxylic acids <90MI 306-02), esters, and nitriles <92MI 306-03) have been described. 

When the reactivity of reactant (R-CH2-X) is relatively high, the condensation reactions take place more easily than the degradation reactions. As a result, the selectivity to the condensation products becomes high. This is the case of the reaction with aldehydes or ketones. The reaction with carboxylic acids and esters is more difficult and the reaction with nitriles is the most difficult especially in view of the selectivity based on HCHO. 

Kaminski has noted that partial substitution of chlorine atoms in TCT 3 by methoxy or phenoxy groups changes the course of the reaction with carboxylic acids <1985TL2901>. In fact, instead of the expected acyl chlorides, the reaction between 2-chloro-4,6-dialkoxy-[l,3,5]-triazine 295 and carboxylic acids gave highly reactive 2-acyloxy-4,6-dialkoxy-[l,3,5]-triazine 296, which, under further treatment with amines, alcohols, and carboxylic acid anions, afforded amides, esters, and anhydrides, respectively (Scheme 57). 

Reaction with Carboxylic Acids and Esters. The reaction of carboxylic acids and esters with Tf20 takes place according to... 

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