Carboxylic acids, with alcohols acid catalyzed

Silylation of alcohols, amines and carboxylic acids with hydrosilanes is catalyzed by Pd catalysts[l 19], Based on this reaction, silyl protection of alcohols, amines, and carboxylic acids can be carried out with /-butyldimethylsilane using Pd on carbon as a catalyst. This method is simpler and more convenient than the silylation with /-butyldimethylsilyl chloride, which is used commonly for the protection. Protection of P-hydroxymethyl-(3-lactam (125) is an example 120]. 

Caglioti et al.201 suggested a mechanism for the action of hexachlorocydotriphos-photriazene in the polyesterification of carboxylic acids with phenols. Higashi291 catalyzed the reaction of various aromatic acids and alcohols by poly(ethyl phosphate). Both Caglioti201 and Higashi291 studied the influence of tertiary amines on the reactivity. 

OXIDATION OF PRIMARY ALCOHOLS TO CARBOXYLIC ACIDS WITH SODIUM CHLORITE CATALYZED BY TEMPO AND BLEACH 4-METHOXYPHENYLACETIC ACID... 

Taft based his steric effect constants on the assumption that rates of esterification of carboxylic acids with alcohols and of acid catalyzed hydrolysis of carboxylate... 

One of the most important chemical transformations of carboxylic acids is their acid-catalyzed reaction with an alcohol to yield an ester. Acetic acid, for example, reacts with ethanol in the presence of H2SO4 to yield ethyl acetate, a widely used solvent. The reaction is a typical carbonyl-group substitution, with -OCH2CH3 from the alcohol replacing -OH from the acid. 

Zhao, M. Li,J. Mano, E. Song, Z. T chaen, D. M. Grabowski, E.J.J. Reider, P.J., Oxidation of Primary Alcohols to Carboxylic Acids with Sodium Chlorite Catalyzed by TEMPO and Bleach. ... 

Esterification. Add-catalyzed esterification of carboxylic acid with alcohol produces water as a coproduct. However, a greener method of esterification of carboxylic acid is via the addition of olefin, which does not produce any co-products and therefore, displays 100% atom efficiency. Proton-exchanged montmorillonite (H+-mont) can be used as a catalyst for addition reactions of carboxylic acids to alkenes (Fig. 7) (38)a). For example, the reaction of benzoic acid with norbomene in the presence of the H+-mont catalyst gave 2-benzoyloxynorbomane. Even with less-reactive simple alkenes, such as cyclopentene and cyclohexene, the corresponding esters were obtained in excellent yields. 

Anhydrides react with water to generate carboxylic acids, with alcohols to give esters, and with amines to form amides. Esters behave similarly. There are both acid-catalyzed and base-induced reactions of esters with water (ester hydrolysis) to give carboxylic acids. There are both acid- and base-catalyzed versions of the reaction of esters with alcohols (transesterification) that generate new esters. Esters also react with amines to form amides. 

FIGURE 3.18 Protection of carboxyl groups by esterification of amino acids (A) by acid-catalyzed reaction with alcohol. [Curtius 1888, Fisher 1906] with X = Cl for H-Xaa-OMe, X-Xaa-OEt, and H-Pro-OCH2Ph ... 

Th effect of pH on the rate of hydrogenation of water-soluble unsaturated carboxylic acids and alcohols catalyzed by rhodium complexes with PNS [24], PTA [29], or MePTA r [32] phosphine ligands can be similarly explained by the formation of monohydride complexes, [RhHPJ, facilitated with increasing basicity ofthe solvent. 

In a similar approach, Kasture and coworkers describe the use of neat substrate (ethyl acetate both as alcohol donor and as the reaction medium) in the preparation of chirally pure S-(-)-l,4-benzodioxan-2-carboxylate, an important drug intermediate used in the synthesis of doxazosin mesylate, from racemic l,4-benzodioxan-2-carboxylic acid [138]. Again, CaLB catalyzed the transesterification reaction with good enanhoselectivity (E = 160) and acceptable enantiomeric excess (>95%) and chemical yield (50%). 

The reaction typically gives 60% to 70% of the maximum yield. The reaction is a reversible process. An ester reacting with water, giving the carboxylic acid and alcohol, is called hydrolysis it is acid catalyzed. The base-promoted decomposition of esters yields an alcohol and a salt of the carboxylic acid this process is called saponification. 

Besides ruthenium tetroxide, other ruthenium salts, such as ruthenium trichloride hydrate, may be used for oxidation of carbon-carbon double bonds. Addition of acetonitrile as a cosolvent to the carbon tetrachloride-water biphase system markedly improves the effectiveness and reliability of ruthenium-catalyzed oxidations. For example, RuCl3 H20 in conjunction with NaI04 in acetonitrile-CCl4-H20 oxidizes (Ej-S-decene to pentanoic acid in 88% yield. Ruthenium salts may also be employed for oxidations of primary alcohols to carboxylic acids, secondary alcohols to ketones, and 1,2-diols to carboxylic acids under mild conditions at room temperature, as exemplified below. However, in the absence of such readily oxidized functional groups, even aromatic rings are oxidized. 

The acetalization of aldehydes and ketones with alcohols is catalyzed by SbCb in the presence of Fe or Al (Scheme 14.5) [21]. The selective acetahzation of aldehydes can also be performed by combined use of Sb(OR)3 (R=Et, iPr) and allyl bromide [26]. Sb(OEt)3 promotes intermolecular amidation between amines and esters or carboxylic acids [27]. When tetraamino esters are used as substrates, the antimony(Ill)-templated macrolactamization occurs to yield macrocychc spermine alkaloids (Scheme 14.6). 

This divergent oxidative reactivity of alcohols and carboxylic acids with olefins is illustrated in Equation 16.103. Bofli reactions generate products from p-hydrogen elimination of an alkoxyalkyl or acetoxyalkyl complex. However, the vinyl ether product generated by p-hy-drogen elimination undergoes reaction with a second equivalent of alcohol to form the acetal in a process catalyzed by the acidic medium or the action of palladium(II) as Levris add. 

Palladium-catalyzed intermolecular oxidations of dienes with carboxylic acids and alcohols as donors give 1,4-addition products. This chemistry has been studied extensively by Backvall. Early studies involved 1,4-additions of two acetoxy or alkoxy groups across a diene,More recently, intermolecular additions of two different nucleophiles have been developed. The ability to control the stereochemistry of the additions across cyclic dienes makes this procedure particularly valuable. As shown in Scheme 16.25, conditions for either cis or trans additions have been developed. Reactions conducted in the absence of added chloride form products from trans 1,4-addition, while reactions conducted in the presence of added chloride form products from cis 1,4-addition. 

In 2007, Ali, et al. studied the esterification of 1-propanol with propionic acid catalyzed by Dowex 50Wx8-400. The experiments were carried out over a temperature range of 303.15-333.15K, and the reaction mechanism for the esterification was proposed (Lilja et al., 2002). The reaction is initiated by the transfer of a proton from the catalyst to the carboxylic acid and the carbonium ion is formed during the reaction. The ion is accessible for a nucleophilic attack by the hydroxyl group from the alcohol. After that, a molecule of water is lost from the ion. Finally, the catalyst is recovered by the transfer of proton from the ion to the catalyst surface. This mechanism is represented by the following scheme (Figure 11) ... 

Reactions of isocyanates with alcohols are catalyzed by a variety of compounds, including bases (tertiary amines, alkoxides, and carboxylates), metal salts and chelates, organometallic compounds, acids, and urethanes. The most widely used catalysts in coatings are organotin (IV) compounds, most commonly dibutyltin dilaurate (DBTDL) (dibutylbis[(l-oxododecyl)oxy]stannate) [77-58-7] and tertiary amines, commonly diazabicyclo[2.2.2]octane (DABCO). Combinations of DABCO and DBTDL often act synergistically. 

Emil Fischer was the first to discover that an ester could be prepared by treating a carboxylic acid with excess alcohol in the presence of an acid catalyst, so the reaction is called a Fischer esterification. Its mechanism is the exact reverse of the mechanism for the acid-catalyzed hydrolysis of an ester shown on page 742. Also... 

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