Caiboxylic acid esters

The most common O- and N-acylation procedures use acylating agents that are more reactive than caiboxylic acids or their esters. Carboxylic acid chlorides and anhydrides react rapidly with most unhindered hydroxy and amino groups to give esters and amides, respectively ... 

Esters aie more easily reduced than caiboxylic acids. Two alcohols aie fonned from each ester molecule. The acyl group of the ester is cleaved, giving a primary alcohol. 

The thennal decarboxylation of malonic acid derivatives is the last step in a multistep synthesis of caiboxylic acids known as the malonic ester synthesis. This synthetic method will be described in Section 21.7. 

Pteridine-4-caiboxylic acid, 2-amino-ethyl ester, 3, 277... 

CN [6/f-[3(Z),6a,7p(Z)]]-7-[[(2-amino-4-thiazolyl)(methoxyi mi no)acetyl]amino]-3-[2-(4-methyl-5-thiazolyl)ethenyl]-8-oxo-5-thia-1 -a7.abicyclo[4.2.0]oct-2-ene-2-caiboxylic acid (2,2-dimethyl-1-oxopropoxy)methyl ester... 

The Kharasch-Sosnovsky reaction may be carried out in the presence of caiboxylic acids to introduce the acyloxy moiety of the acid used, and may also be conducted photochemically at room temperature using UV irradiation. Peroxy acids, diacyl peroxides, and peroxyphosphates and peroxyphospho-nates are alternative oxidants. r-Butyl hy operoxide may also be used in place of peroxy esters with broadly similar results, although formations of mixed peroxides and r-butyl ethers can then compete with allyl ester production. 

Finally, some of the methods for carboxylic acid reduction (Section 1.12.2) have also been applied to esters. Thus, the ethyl ester of thiazole-2-caiboxylic acid has been reduced electrochemically to the corresponding aldehyde, and some of the high temperature metal oxide catalyzed hydrogenations have been used on esters. ... 

The reaction of activated aziridine-2-caiboxylic acid methyl esters (169) with ethoxycarbonylmethyl-enetriphenylphosphorane resulted in the formation of phosphorane (170) along with phosphorane (171) and aziridine (172), with the exception of (169d), where (172d) was obtained as the sole product (Scheme 74). Phosphorane (170b) was converted into 4-methylene-(2S)-glutamic acid (173). ... 

R-Hydroxy-22-desoxyecdysone, 23, 24 2 -Hydioxydiphenyl-2-caiboxylic acid lactone, 154-155 j3-Hydroxy esters, 172—173 7-Hydroxyketones, 91 Hydroxylamine, 99... 

Section 315 (Caiboxylic Acid - Amide) Section 316 (Carboxylic Acid - Amine) Section 351 (Amine - Ester)... 

Esters are carboxylic acid derivatives in which the hydroxyl group (—OH) is replaced by an alkoxy group (—OR). An ester is a combination of a caiboxylic acid and an alcohol, with loss of a molecule of water. We have seen that esters can be formed by the Fischer esterification of an acid with an alcohol (Section 20-10). 

It has been used for stereo and/or regio selective dipolar cycloadditions, e.g. with chiral aciylamides it produces 2A-pyrazoline caiboxylic acids (azaprolines) after protio-desilylation [Mish et al. J Am Chem Soc 119 8379 7997], or with diethyl /rani -glutacoiiate where the pyrazoline ester is oxidised to the respective pyrazole [Di Rein Tetrahedron Lett 45 4703 2004], It also acts as a caibene sonrce in stereoselective [1 + 4] annulation reactions with silylvinylketenes to form a variety of cyclopent-2-enones in good to excellent yields [Moser et al. J Org Chem 71 6542 2006. ... 

The amination of the a-carbon atom of caiboxylic acid derivatives has been extensively studied by Ef-fenberger and cowoikers. Ethyl (5)-a-bromopropionate reacted with (/ )- -phenylethylamine to give (2RXR)- and (25,r )-/V-(l -phenylethyl)alanine ethyl ester, e.g. (2/ ,l / )-(4) and (2S,l / )-(4). Prolonged reaction time afforded the products in higher yields with decreasing stereospecificity (Scheme 5). 

In most scenarios, the interaction proceeds in steps, i.e., equilibrium solution represents the mixture of heteroassodates of different stoichiometry AB, AB2, A2B, etc. Systems formed by 0-, S-, N-, P- bases with various H-donors (e g., amines-eaiboxylic acids, esters-caiboxyhc acids (phenols), dimethylsulfoxide-caiboxylic acid) refer to this type of interactiom... 

C16H18 02 naphtlialene-2-caiboxylic acid pentyl ester 2876-80-4 ... 

Section 20.17 Like ester hydrolysis, fflnide hydrolysis can be achieved in either aqueous acid or aqueous base. The process is ineversible in both media. In base, the carboxylic acid is converted to the caiboxylate anion in acid, the fflnine is protonated to an ammonium ion ... 

Step 1 The Boc-protected amino acid is anchored to the resin. Nucleophilic substitution of the benzylic chloride by the caiboxylate anion gives an ester. 

One important group of condensation polymers is the polyesters. The most important commercial polyester is formed from the reaction of terephthalic acid (a diacid) with ethylene glycol (a diol). This polymerization occurs in a stepwise fashion (hence the name step growth polymerization). First, one carboxylic acid group of a diacid molecule and one hydroxy group of a diol molecule combine to form an ester, with the loss of water. Then a second diol molecule reacts with the unreacted caiboxylic group on the other end of the diacid molecule, or a second diacid molecule reacts with the unreacted hydroxy group of the diol. Continuation of this process adds a new monomer unit at... 

Uncertainties in identifying specific functional groups results in a range of n. The lower limit considers all aromatic carbon to be nonprotonated, the oxygen-substituted carbon to be a tertiary ether, the caiboxylate to be an ester, and the carbonyl to be a ketone. The upper limit is derived by assuming that all the aromatic carbon is protonated, the oxygen-substituted carbon is a primary alcohol, and the carboxylate is an acid. 

As the caiboxylate moieties of vinyl esters increase in length, the degree of branching due to chain transfer to both monomer and polymer increases. The relationship between the chain-transfer constant (C.T.) and the number of carbon atoms in the caiboxylate portion of a fatty acid vinyl ester in the presence of vinyl acetate is given by the expression... 

Other acylating agents are similarly effective in the formation of ketones by reaction with homocuprates. Kim has demonstrated that activated esters such as the 2-pyridyl caiboxylates are satisfactory cuprate traps.These esters can be prepared from carboxylic acids and 2-pyridyl chloroformate, provided a catalytic amount of DMAP is utilized (Scheme 33). 

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