Esters beta-ketonic

REACTIONS OF MONOSACCHARIDES WITH BETA-KETONIC ESTERS 101... 

First, peak heights are measured at five points in the NMR spectra (Figure 2). All NMR spectra of fulvic acids described in this study were determined as the sodium salt in D20 at pH 8 (21). Peak heights were used rather than peak areas to minimize overlapping spectral contributions from various proton structures. From structural-model considerations, peak 1 appears to be a combination of methylene and methine protons in aliphatic alicyclic rings and branched methyl groups located beta to carbonyl groups of a carboxylic acid, ester, or ketone. The structural model rules out meth-... 

Garcia Gonzalez, F Reactions of Monosaccharides with beta-Ketonic Esters and Related Substances, 11, 97-143... 

This corresponds to pyro-racemic acid in being the simplest beta-ketone acid possible. While it is known in the free state as an easily decomposed hygroscopic syrup its principal form is as the ethyl ester CH3—CO—CH2—COOC2H5, ethyl aceto acetate. In this form it is prepared and in this form it is used as a synthetic reagent. The ester is a colorless liquid boiling at 181°, with a characteristic fruity odor. 

Coumarin synthetic routes include Perkin, Knoevenagel, Reformatsky, and Pechmann reactions. Among them Pechmann reaction has been proven to be superior regarding different issues and aspects. Pechmann found that coumarin derivatives are synthesized when the P-ketonic esters are condensed with phenols in the presence of concentrated sulfuric acid. The process and course of this reaction depends on the nature of the phenols, the beta-ketonic esters, and the catalyst. Since then, the use of this superior and practical protocol has become a vibrant area of study, and it has found applications as central strategic choice in the synthesis of an extensive selection of coumarin derivatives. 

For a general, simple high yield indole synthesis from anilines and methylthioacetaldehyde etc. see JACS 95,588,591,2718,6508 (1973). For indoles from N-( /3 -hydroxy-ethyl aniline esters see BSC 2485(1973). For a 2-acyl-indoles in one step from orthoamino-ketones and alpha-haloketones or 2-carboxyindoles from sulfonamides of ortho-aminocarbonyls see JOC 38,3622-24(1972). Indole and 5-Br-indole in 4 steps from beta-naphthol see Chem. Het. Cpds. (Russ.) 753(1973). Indole-JOC 37,3622(1972). 

Group-transfer polymerizations make use of a silicon-mediated Michael addition reaction. They allow the synthesis of isolatable, well-characterized living polymers whose reactive end groups can be converted into other functional groups. It allows the polymerization of alpha, beta-unsaturated esters, ketones, amides, or nitriles through the use of silyl ketenes in the presence of suitable nucleophilic catalysts such as soluble Lewis acids, fluorides, cyanides, azides, and bifluorides, HF. ... 

Beckman EJ, Munshi P (2011) Ambient caiboxylation on a supported reversible C02 carrier ketone to [beta]-keto ester. Green Chem 13(2) 376-383... 

Phenylglyoxylate esters undergo type II elimination in a unique fashion in that the alcohol portion is oxidized to a ketone or aldehyde while the benzoylcarboxy portion forms a hydroxyketene [18]. The intermediate 1,4-biradicals do not cyclize, presumably because of the strain in a beta-lactone. 

Based on the above discussion it was thought that the trifluoro-methyl ketones would be more polarized and thus create a great electrophilicity on the carbonyl carbon which facilitates -OH attack by the serine residue. Yet there is no carbon-oxygen bond to be cleaved In the ketone moiety, and therefore the enzyme-trifluoromethyl ketone transition state complex does not undergo catalytic conversion. The above rationale seems reasonable as trifluoromethyl ketones were found to be extraordinary selective and potent inhibitors of cholinesterases (56) of JHE from T. ni (57) and of meperidine carboxylesterases from mouse and human livers (58). Since JH homologs are alpha-beta unsaturated esters, a sulfide bond was placed beta to the carbonyl in hopes that it would mimic the 2,3-olefln of JHs and yield more powerful inhibitors (54). This empirical approach was extremely successful since it resulted in compounds that were extremely potent inhibitors of JHEs from different species (51,54,59). 

Stirring an ester in an aqueous suspension of Dowex-50 is an efficient method for hydrolyzing the ester to the acid. Similar results have been obtained by refluxing an ester in an aqueous suspension of H-beta zeolite. Stirring acetals in an acetone suspension of wet silica gel or moistened Amberlyst-15 0 is a convenient method for converting an acetal to the aldehyde or ketone without having side reactions such as double bond isomerizations also take place (Eqn. 22.40). 9... 

The Knorr Pyrrole Synthesis. In this process, the starting materials are an alpha-amino ketone, or less commonly an alpha-amino aldehyde, and a beta-ketoester. In the latter, the protons on the alpha carbon are activated both by the keto and the ester carbonyls and are especially easily removed. The Knorr process starts with the condensation of the amino group with the keto group in the usual way to tie the two molecules together as in 4.29 of the example shown in Scheme 4.31. This species then undergoes intramolecular aldol-type condensation to form a reduced pyrrole derivative 4.30. 

Organic compounds, in order of decreasing radiation resistance, are aromatics, aliphatics, alcohols, amines, esters, ketones, and acids. Extension to beta radiation is probably reasonable. In tritium gas, however, substantial differences in irradiation or polymer surface as compared to bulk can occur. This results from the greater density of tritium (and the much greater range of the beta in the tritium gas) outside the polymer compared to inside the polymer bulk. 

One of the functions of hepatic P-oxidation is to provide ketone bodies, acetoac-etate and p-hydroxybutyrate, to the peripheral circulation. These can then be utilized by peripheral tissues such as brain and heart. Beta-oxidation itself produces acetyl-CoA which then has three possible fates entry to the Krebs cycle via citrate S5mthase keto-genesis or transesterification to acetyl-carnitine by the action of carnitine acetyltrans-ferase (CAT). Intramitochondrial acetyl-carnitine then equilibrates with plasma via the carnitine acyl-camitine translocase and presumably via the plasma membrane carnitine transporter. Human studies have shown that acetyl-carnitine may provide up to 5% of the circulating carbon product from fatty acids and can be taker and utilized by muscle and possibly brain." In addition, acyl-camitines are of important with regard to the diagnosis of inborn errors of P- oxidation. For these reasons, we wished to examine the production of acetyl-carnitine and other acyl-camitine esters by neonatal rat hepatocytes. 

A further important development in the use of silica zeolite polymorphs containing Lewis acid sites in the framework in selective oxidation reactions was made by the group of Corma. They found that tin-containing zeolite Beta is a highly selective catalyst for Baeyer-Villiger oxidations, in which ketones are oxidised by hydrogen peroxide to give esters or lactones (Scheme 9.8). ... 

Beta-keto esters can be prepared by treating the enolate of a ketone with diethyl carbonate. Draw a plausible mechanism for this reaction. 

Unsymmetrical sulfides possessing carbonyl groups beta to sulfur have been prepared by Michael addition of thiols to a,i8-unsaturated aldehydes, ketones, and esters in tetrahydrofuran under phase transfer conditions [17] (see Eq. 13.8). This reaction is catalyzed by fluoride ion. In this application, tetrabutylammonium fluoride (TBAF)... 

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