Functionalized carboxylate

Hexafluoroacetone and certain perfluorinated or partially fluorinated ketones, aldehydes, and imines react with a-functionalized carboxylic acids (e.g., a-amino, a-At-methylamino [S3, 84], a-hydroxy [S5], and a-mercapto [Sd] acids) to give five-membered heterocyclic systems (equation 13). 

Self-assembly of functionalized carboxylate-core dendrons around Er +, Tb +, or Eu + ions leads to the formation of dendrimers [19]. Experiments carried out in toluene solution showed that UV excitation of the chromophoric groups contained in the branches caused the sensitized emission of the lanthanide ion, presumably by an energy transfer Forster mechanism. The much lower sensitization effect found for Eu + compared with Tb + was ascribed to a weaker spectral overlap, but it could be related to the fact that Eu + can quench the donor excited state by electron transfer [20]. 

The transformation has a broad scope, and higher oligopeptides can easily be obtained using higher functionalized carboxylic acids and/or isocyanides as starting materials [19]. The only disadvantage is the modest diastereoselectivity of approximately 2 1. 

Imidazole-functionalized carboxylate ion micelles. Rate comparisons... 

The last work pertaining to the discovery of new catalysts is perhaps the most novel approach to be reported thus far. In one of the earliest approaches taken toward catalyst development, Menger et al. (61) attempted to find catalysts for phosphate ester hydrolysis. A series of eight functionalized carboxylic acids were attached to polyallylamine in various combinations. Each of these polymers were then treated with one of three metals, Mg2+, Zn2+, or Fe3+. The different members of each library were identified by the relative percentages of each carboxylic acid attached to the polyamine. For example, one polymer possessed 15% Oct, 15% Imi, 15% Phe, and 5% Fe3+. There is no attempt to identify the location of the various carboxylic acids in a given polymer. This approach is novel since each system consists of an ensemble of different ligands with the carboxylic acids positioned in various locations. Each polymer within a given ratio of carboxylic acids consists of a combinatorial library of potential catalysts. 

Preparahon of functional carboxylic acid and aldehyde groups see below. 

Reactions presented below show that this method is used frequently to prepare magnesium enolates derived from functionalized carboxylic esters or lactones (equations 18-24, Tables 2 and 3). 

Zircoaluminates (ZAs) constitute a unique class of bifunctional additives which are synthesized in accordance with a highly specific procedure [4-6] to produce stable covalent molecules. As shown below, the essential chemistry involves the reaction of two solid inorganic raw materials with a number of different functionalized carboxylic acids in the presence of selected solvents [reaction (2)]. 

This methodology has been extended by employing functionalized carboxylic acids and/or isocyanides in order to increase the diversity of the reaction products and to achieve an easy access to four- or five-unit peptide mimetics [28]. For example, tetrapeptide 36 was obtained in 59% overall yield (Scheme 2.14). 

Kulik et al. [205] focused their studies on the identification of chemical species formed during the treatment of polyolefins such as polyethylene or polypropylene by gaseous ozone or ozone in aqueous medium. Experimental conditions have a great influence on the nature of the obtained species. For example, peroxidic functions, carboxylic acids, and ketones have been identified, aldehydes being absent of the surface of the materials. It must be noted here the instability of the peroxidic species formed during the treatment... 

Fig. 2.27. Stereoselectivity due to neighboring group participation in the synthesis of a-functionalized carboxylic acids.

A recent synthesis of ( )-cordrastine used as a key step the formation of aryllithium 86 in the presence of the hydroxyl and amino functions. Carboxylation of 86 and lactonisation gave the natural product.78... 

This reaction can be extended to unsaturated nitriles, eg, acrylonitrile, which can give trihalostannyl-functional carboxylic acids, esters, and amides by the proper choice of solvents and reaction conditions (156). 

Acid-catalyzed S—O fission may occur under neutral conditions under the influence of enzymic catalysis. Perhaps a functional carboxyl group obtains at the active site of the enzyme, a group which occurs in undissociated acid form and works as a powerful acid catalyst because of its location at a special hydrophobic pocket. However, we have examined other possibilities of metal-ion-catalyzed S—O fission. 

In a similar way, other derivatives of diamines (S,S)-28 and (R,R)-29 were evaluated for their gelation properties. As an example, trans-(R,R) 1,2-bis(dodecy-lureido)cyclohexane and trans-(R,R)-1,2-bis(octadecylureido)cyclohexane can cause physical gelation in a wide variety of organic solvents [76]. As an extension of these studies, novel polymerizable organogelators based on tra s-(7 ,7 )-l,2-bis(ur-eido)cyclohexane derivatives have been reported [77]. In these molecules, the presence of methacrylate-functionalized carboxylic acid groups determines the... 

In addition, Song et al. (76) used a one-step condensation synthesis method to prepare the PLA-MWCNTnanocomposites. For detailed experimental conditions, refer to Song et al. (76). The nanocomposites were prepared using pure and carboxylic-acid-functionalized MWCNTs. As with the other studies, the carboxylic-acid-functionalized MWCNTs dispersed better in PLA compared with non-functionalized MWCNTs. Overall, it can be inferred from the studies described in this section that the functionalization of MWCNTs is a very important step in the process of making a nanocomposite, as it will help to disperse the nanotubes uniformly, which will eventually create the superior properties of the resulting nanocomposite. In addition, among the currently available methods for functionalization, carboxylic-functionalization is the best for uniform dispersion. 

Some other capsules have been described in which both complimentary functions, carboxylic acids and nitrogen-containing aromatic rings, are respectively attached to the rims of two bowl-shaped molecules. Reinhoudt has prepared selfassembling, multi-hydrogen bonding molecular capsules in which a calix[4]arene substituted with four carboxylic functions at the upper rim interacts with a complimentary calix[4]arene with four pyridines attached to the lower rim. These capsules have been identified by H-NiMR, IR and VPO measurements but encapsulation properties have not been reported [106]. 

M. Viertelhaus, R. Hilfiker, F. Blatter, Piracetam co-crystals with OH-group functionalized carboxylic acids, Cryst. Growth Des. 9 (2009) 2220-2228. 

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