Aliphatic ester synthesis

Raghavan and coworkers have reported on the preparation of 4-hydroxybenzoic add esters (parabans) possessing antimicrobial activity by esterification of 4-hydroxybenzoic acid (Scheme 6.153) [299]. Optimum results were obtained using the alcohol (1-butanol) as solvent in the presence of catalytic amounts of zinc(II) chloride or p-toluenesulfonic acid (pTsOH) under atmospheric conditions. After 5 min of microwave irradiation at 120 °C, ca. 40% conversion to the ester was observed. Related studies on the synthesis of long-chain aliphatic esters have been described by Mariani and coworkers [300]. 

Using what is perhaps the most efficient laboratory-scale synthesis to-date, Frechet et al. have prepared a family of ABA hybrids with aliphatic ester dendron A blocks and PEG B block. These non-toxic hybrids are being tested as drug delivery vectors [47],... 

The reason why the acyloin synthesis is especially characteristic of aromatic aldehydes, depends on the circumstance that in the aromatic series the tertiary carbon atom in the ring does not allow of the aldol condensation, a reaction for which conditions are otherwise much more favourable. The simplest example of the acyloin condensation, moreover, was already encountered in the case of formaldehyde (p. 218) glycollic aldehyde is the simplest acyloin. Acyloin compounds are also produced, in the aliphatic series, by the action of sodium or potassium on esters, and hence are also formed as by-products in the acetoacetic ester synthesis (Bouveault, Scheibler). 

This method for preparing 2-phenyl-1-pyrroline, and assorted 2-substituted 1-pyrrolines, is one of the best currently available, particularly because it reproducibly affords clean materials. Generally, the procedure is amenable to various aromatic esters 2 it has also been applied successfully to aliphatic esters (Table I).3 An advantage of this method is the use of readily available, inexpensive N-vinyl-pyrrolidin-2-one as a key starting material. This compound serves effectively as a 3-aminopropyl carbanion equivalent. The method illustrated in this procedure has been extended to include the synthesis of 2,3-disubstituted pyrrolines. Thus, alkylation of the enolate of the intermediate keto lactam, followed by hydrolysis, leads to various disubstituted pyrrolines in good yields (see Table II).3... 

Hudson, B. E., and Ch. R. Hauser Condensations. XVI. Various Acylations and Alkylations of the Sodium Enolates of Aliphatic Esters. Methods for the Synthesis of a,a-Disubstituted j -Keto Esters and of Certain Other Compounds. J. Amer. chem. Soc. 63, 3156 (1941). 

It is not possible to perform the acid hydrolysis without some ketonic hydrolysis occurring. This reaction and the preceding one are important in many syntheses of aliphatic ketones and acids. They might have been included equally well in the decomposition section (p. 411) in fact they are often referred to as the ketonic and acid decomposition of acetoacetic ester. The malonic ester synthesis of fatty acids may be compared with the present reaction (p. 135). 

The polymer-assisted solution-phase (PASP) synthesis of a 192-member group of 1,5-biaryl pyrazoles from 1,3-diketones and 4-hydrazinobenzoic acid as precursors has been reported <2004JC0332>. Condensation of aromatic or aliphatic esters with resin-supported sulfonamides 527, followed by cyclization with hydrazines, activation with trimethylsilyldiazomethane, and cleavage using amines, provided highly substituted, isomeric pyrazoles 528 and 529 (Scheme 63) <20000L2789>. 

Kashimura, S., Mural, Y., Ishifune, M., Masuda, H., Murase, H., Shono, T. Electroorganic chemistry. 148. Cathodic coupling of aliphatic esters. Useful reaction for the synthesis of 1,2-diketone and acyloin. Tetrahedron Lett. 1995, 36, 4805-4808. 

Nitrenes as intermediates in synthesis of N-heterocycles 82MI14. Nitroacetic acid and its esters in synthesis of N-heterocycles 79S666. Nitro compounds of aliphatic series, synthesis of N-heterocycles from ... 

Homoeyelic ring closures. Bunnett and Skorcz31 found that several aliphatic esters, nitriles, sulfones, and ketones bearing an m-o-chlorophenyl group react with potassium amide in liquid ammonia to form homocyclic products of ring closure by way of a benzyne intermediate. The procedure has since been modified to use sodium amide (commercially available).32 The reaction is probably the method of choice for synthesis of 1 -substituted benzcyclobutenes. 

The oxidative esterification of aldehydes in the presence of alcohols to produce saturated and unsaturated aliphatic esters has been developed at the Nippon Shokubai laboratories a great result is represented by the new synthesis of methylmethacrylate (MMA) from methacrolein, methanol and molecular oxygen, which allows yields up to 50 mol MMA (kg cat)" h" using supported bimetallic gold catalysts under relatively mild conditions (80 °C and 3 MPa) [7]. 

This reaction was first reported by Bouveault and Blanc in 1903, and was further extended by Bouveault and Locquin. It is the synthesis of symmetrical a-hydroxy ketones via the reductive condensation of esters in an inert solvent in the presence of sodium. Since symmetrical a-hydroxy ketones, the aliphatic analogs of benzoins, are generally known as acyloins, the formation of a-hydroxy ketones from esters is simply referred to as acyloin condensation. In a few cases, it is also referred to as acyloin reaction." For the individual acyloin, the name is derived by adding the suffix oin to the stem name of corresponding acid, e.g., acetoin prepared from acetate. The most common method used to make acyloin is the reductive condensation of aliphatic esters with sodium in inert solvents, such as ether, xylene or even in liquid NH3 The yield of this reaction can be greatly improved when trimethylchlorosilane presents." " Intromolecular acyloin condensation from aliphatic diesters affords cyclic ketones of different ring sizes. 

Ihre, H., De Jesus, O.L.P., and Frechet, J.M.J. (2001) Fast and convenient divergent synthesis of aliphatic ester dendrimers by anhydride coupling. J. 

The most common example of this class of plasticizer are the adipate esters, although succinates, gluterates, azelates and sebacates are encountered. The synthesis of these esters is similar to that for phthalate esters. The most commonly employed aliphatic ester is di-2-ethylhexyl adipate (DOA), a very cost effective plasticizer. A comparison of selected performance properties of DOP, DOA and trioctyl trimellitate (TOTM), based on 2-ethyl hexanol, is given in Table 14 (49). 

The acylation of cellulose with acid chlorides in DMA/LiCl is most suitable for the homogeneous synthesis of readily soluble partially functionalized long-chain aliphatic esters and substituted acetic acid esters (Table 16.3). In contrast to the anhydrides, the fatty acid chlorides are soluble in the reaction mixture and soluble polysaccharide esters may be formed with a very high efficiency. Even in the case of stearoyl chloride, 79 per cent of the reagent is consumed for the esterification of cellulose. 

The Pechmann coumarin synthesis, also known as the Pechmann condensation or Pechmann reaction, is the Lewis or Bronsted acid-promoted condensation of phenols (1) and P-keto (or other 3-oxo aliphatic) esters (2) to produce coiunarins (2//-chromen-2-ones, 3). ... 

Enzyunatic synthesis of aliphatic ester copolymers was achieved by lipase-catalyzed polymerization of two lactones. The copolymerization of S-VL and e-CL catalyzed by lipase PF produced the corresponding copolymer having random structure of both units (174). In the copolymerization of OL with e-CL or DDL, random copolyesters were also formed (162), suggesting the frequent occurrence of transesterifications between the polyesters. On the other hand, the copolymer from e-CL and PDL was not statistically random (166). 

The aliphatic carboxylic acids are valuable intermediates in the synthesis of other organic chemicals, resins and polymer compositions. The reaction of a carboxylic acid with an aliphatic alcohol in the presence of an acidic catalyst yields a valuable series of aliphatic ester solvents. The cellulose acetate and... 

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