Ethers with carboxylic acids

Vinyl ethers undergo all of the expected reactions of olefinic compounds plus a number of other reactions. For example, vinyl ethers react with alcohols give acetals. The acetals are stable under neutral or alkaline conditions and are easily hydrolyzed with dilute acid after other desired reactions have occurred. Reaction of a vinyl ether with water gives acetaldehyde and the corresponding alcohol and reaction of vinyl ethers with carboxylic acids gives 1-alkoxyethyl esters and with thiols gives thioacetals. 

Table 3 Acid Chlorides from the Reaction of Dichloromethyl Methyl Ether° with Carboxylic Acids...

Ranu, B. C., Ghosh, K., Jana, U. Simple and Improved Procedure for Regioselective Acylation of Aromatic Ethers with Carboxylic Acids on the Solid Surface of Alumina in the Presence of Trifluoroacetic Anhydride. J. Org. Chem. 1996, 61, 9546-9547. 

Acylation of Aromatic Ethers. A simple and improved procedure for regioselec-tive acylation of aromatic ethers with carboxylic acids on alumina in the presence of trifluoroacetic anhydride has been described by Ranu et al. [Eq. (21)]... 

The same BU4NI/TBHP catalytic system has also been applied towards the a-oxyacylation of ethers with carboxylic acids in ethyl acetate at 80 °C [105], which possibly occurs via a radical mechanism. 

The regioselective acylation of aromatic ethers with carboxylic acids (aromatic ether/carboxylic acid ratio =1) can be pafonned with an equimolecular mixture of trifluoroacetic anhydride adsorbed on the surface of alumina without any solvent [77]. The process can be applied, with nearly quantitative yields, to anisole and the three isomeric dimethoxybenzenes by using carboxylic acids. The authors outline that in the case of anisole, the acylation selectively occurs at the para position to the methoxy group. The reaction requires a large amount of alumina and trifluoroacetic anhydride, and consequently, it can only be appUed at the laboratory scale. The intervention of a mixed carboxyhc acidArifluoroacetic acid mixed anhydride intermediate is presumed. 

Cleavage of ethers with carboxylic acid halides... 

Ethers of benzenepentol have been obtained by Dakin oxidation of the appropriately substituted acetophenone. Thus, the oxidation of 2-hydroxy-3,4,6-ttimethoxyacetophenone and 2-hydroxy-3,4,5-ttimethoxyacetophenone with hydrogen peroxide ia the presence of alkali gives l,2-dihydroxy-3,4,6-ttimethoxybenzene and l,2-dihydroxy-3,4,5-ttimethoxybenzene, respectively further methylation of these ethers yields the pentamethyl ether of benzenepentol (mp 58—59 degC) (253). The one-step aromatization of myoinositol to produce esters of pentahydroxybenzene is achieved by treatment with carboxylic acid anhydrides ia DMSO and ia the presence of pyridine (254) (see Vitamins). 6-Alkyl- or... 

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... 

Acylation The reagent catalyses the arylation of activated aromatic compounds by reaction with carboxylic acids. Thus methyl phenyl ether can be acylated with acetic acid in presence of trifluoroacetic anhydride in good yields. 

A condensation reaction joins two molecules and splits out a small molecule. The small molecule is usually water. The formation of a peptide bond is an example of a condensation reaction. The conditions necessary for a condensation reaction vary with the functional groups involved. In most cases, a catalyst will be present. The two most common catalysts are acids and enzymes. Two alcohols will condense to form an ether. A carboxylic acid condenses with an alcohol to form an ester. A carboxylic acid condenses with an amine to form an amide. 

Methylation. The reaction with diazomethane has often been used for differentiating the acidic groups (28, 35, 38, 45, 46, 69). Diazomethane reacts, in general, with carboxylic acids, forming methyl esters which are easily hydrolyzed by dilute hydrochloric acid. With phenols, ethers are formed which are stable to hydrolysis. Alcohols are methylated only if catalysts are present, e.g., BF, ZnClj (70), or HjO (71). As Garten et al. 

Dissolving metal reductions of the benzene rings are especially important with functional derivatives of benzene such as phenols, phenol ethers and carboxylic acids (pp. 80, 82,93 and 140). 

We have also looked at a no-d case where we have cleaved R3B compounds, triethylboron, with carboxylic acids in an ethereal environment. Once again we have the possibility of coordinating a substance like a carboxylic acid with our boron compound in a six-membered ring,... 

Secondary alkyl ethers can be oxidized to ketones by bromine (e,g., Me2CHOCHMe2 + Br — Me2CO).109 Primary alkyl ethers give carboxylic acids (9-22) with bromine, but can be cleaved to aldehydes with l-chlorobenzotriazole.lln... 

Hydrolysis of carboxylic esters 0-17 Transetherification 0-18 Payne rearrangement 0-23 Transesterification 0-55 Ammonolysis of carboxylic esters 0-68 Cleavage of ethers with concentrated acids... 

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. 

It is possible to prepare esters of phenols with carboxylic acid anhydrides or acid halides, and phenyl ethers by reaction of benzenolate anion with halides, sulfate esters, sulfonates, or other alkyl derivatives that react well by the SN2 mechanism ... 

In the first step amine 11 is coupled with carboxylic acid 15 to form an amide The method employed here for coupling an a-chiral carboxylic acid with an amine was developed in the context of peptide synthesis. Its success is based on DCC-mediated formation (see Chapter 5) of the reactive 1-hydroxy benzotriazole ester 55, which reacts with an amine to give the corresponding amide. In most cases reaction takes place without raccmi/ation, and often in the absence of side reactions that cause other procedures to The alcohol is converted into a silyl ether in the second step. 

For example, EC yields polymers containing blocks of poly-ethers and polycarbonates. due to the partial elimination of C02 [246], while its hydrolysis produces high-purity 1,2-diols. Furthermore, CCs react readily with carboxylic acids to form 2-hydroxyethyl esters [177, 247, 248]. 

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