Alkoxy esters, preparation

A slightly more complex Scheme is required for preparation of an antihistaminic agent bearing a secondary amine, e. g., tofenacin (32). In the synthesis of tofenacin, alkylation of the benzhydrol (29) with ethyl bromoacetate affords the alkoxy ester (30) saponification followed by conversion to the methylamide gives (31), which is reduced with lithium aluminum hydride to complete the synthesis of 32. 10... 

To prepare hexaaluminates for ceramic applications a slightly different sol-gel process was proposed by Debsikbar.19 Ba-hexaaluminates were prepared via hydrolysis of Al di(isopropoxide) acetoacetic ester chelate and anhydrous Ba acetate obtained by reaction between BaC03 and glacial acetic acid. The substitution of Al(i-OC3H7)3 with the alkoxy ester was intended to control the chemical polymerization during gel formation. The reaction was performed in 1-butanol. The formation of the gel slowly occurred at room temperature in about 10 h. To obtain the final phase the gel precursor was dried at 70 °C for about 2 weeks, ground and calcined at 1200°C for 2 h. However no data on the morphology of the final materials were reported by the author. 

The Claisen ester enolate reaction has proved to be extremely useful in the synthesis of a large number of natural products.3 In addition, the rearrangement has been extended to allow the preparation of useful intermediates such as a-alkoxy esters,88 329 33 336 343 a-phenylthio esters,339344-345 a- and [3-amino acids,340 346-350 a-fluoro esters,351 cycloalkenes,352353 tetronic acids,354 and dihydro-pyrans.355-357... 

This reagent is the best promoter of the aldol reaction of 2-(trimethylsiloxy)acry-late esters, prepared by the silylation of pyruvate esters, to afford y-alkoxy-a-keto esters (Eq. 80) [135] These esters occur in a variety of important natural products. 

It is, in fact, likely that Eq. (112) may explain the j3-alkoxy ester formation, whereas Eq. (113) may be the route to methyl acrylate. Thus, preparation of carboalkoxypalladium(II) in situ by exchange with the stable ROOCHgCl in the presence of ethylene gives only acrylate esters (90) ... 

One of the virtues of the Fischer indole synthesis is that it can frequently be used to prepare indoles having functionalized substituents. This versatility extends beyond the range of very stable substituents such as alkoxy and halogens and includes esters, amides and hydroxy substituents. Table 7.3 gives some examples. These include cases of introduction of 3-acetic acid, 3-acetamide, 3-(2-aminoethyl)- and 3-(2-hydroxyethyl)- side-chains, all of which are of special importance in the preparation of biologically active indole derivatives. Entry 11 is an efficient synthesis of the non-steroidal anti-inflammatory drug indomethacin. A noteworthy feature of the reaction is the... 

The tartrate ester modified allylboronates, the diisopropyl 2-allyl-l,3,2-dioxaborolane-4,5-di-carboxylates, are attractive reagents for organic synthesis owing to their ease of preparation and stability to storage71. In the best cases these reagents are about as enantioselective as the allyl(diisopinocampheyl)boranes (82-88% ee with unhindered aliphatic aldehydes), but with hindered aliphatic, aromatic, a,/l-unsaturated and many a- and /5-alkoxy-substituted aldehydes the enantioselectivity falls to 55-75% ee71a-b... 

Amine salts of acrylate ester polymers, which are physiologically acceptable and useful as surfactants, are prepared by transesterification of alkyl acrylate polymers with 4-morpholinethanol or the alkanolamines and fatty alcohols or alkoxy-lated alkylphenols, and neutralizing with phosphoric acid. The product was used as an emulsifying agent for oils and waxes [60]. 

An important group of acylation reactions involves esters, in which case the leaving group is alkoxy or aryloxy. The self-condensation of esters is known as the Claisen condensation.216 Ethyl acetoacetate, for example, is prepared by Claisen condensation of ethyl acetate. All of the steps in the mechanism are reversible, and a full equivalent of base is needed to bring the reaction to completion. Ethyl acetoacetate is more acidic than any of the other species present and is converted to its conjugate base in the final step. The (3-ketoester product is obtained after neutralization. 

Using azolides, thiazolidindiones can be prepared by condensation of alkoxy-carbamoylimidazoles obtained in situ from O-alkylhydroxylamines and CDI with thio-glycolic acid methyl ester or the imidazolide of thiolactic acid obtained in situ from thiolactic acid and CDI [121]... 

This compound can disproportionate, generating silane (SiH4) which is liable to be pyrophoric. Presumably other alkoxy silanes can do likewise [ 1 ]. Its use as a reducing agent for the preparation of alcohols from esters is considered safer in air than under... 

That being said, it must be recognized that the evidence that the (V-acy I isourea is the precursor of the 2-alkoxy-5(4//)-oxazolone is only circumstantial because experiments starting from the former have yet to be achieved. The oxazolone could theoretically come from the symmetrical anhydride. The latter generates 2-alkoxy-5(4//)-oxazolone in the presence of tertiary amines (see Section 4.16) even dicy-clohexylcarbodiimide (DCC) was basic enough to generate 2-t< rt-butoxy-5(4 )-oxazolone from Boc-valine anhydride. However the weight of evidence points to O-acylisourea as the precursor of the 2-alkoxy-5(4//)-oxazolone. In the absence of. V-nucleophile, such as in the preparation of esters, the major precursor of product is the symmetrical anhydride.7,8... 

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