Homologation Of Esters Research Articles

Ligand exchange reaction of sulfoxides in organic synthesis: A new synthesis of α-chloroketones from carbonyl compounds with one-carbon homologation

A new procedure for one-carbon homologation of carbonyl compounds to α-chloroketones is described. Addition of the carbanion of dichloromethyl phenyl sulfoxide with ketones and aldehydes gave the adducts, chloro alcohols, in good yields. Treatment of the chloro alcohols with EtMgBr or lithium diisopropylamide gave one-carbon homologated α-chloroketones via β-oxido carbenoid rearrangement in moderate to good yields. One-carbon homologation of esters to α-chloroketones was realized via the ligand exchange reaction of the sulfinyl group of α-chloro α-sulfinyl ketones, which were synthesized from methyl esters and chloromethyl phenyl sulfoxide, with EtMgBr.

Homologation of representative boronic esters using in situ generated (halomethyl)lithiums: A comparative study

A comparative study of the homologation of representative boronic esters with in situ generated LiCH 2X (X= Cl; Br; I) is presented wherein the reactivity differences arising out of the steric and electronic effects of the migrating groups, and the nature of the ester groups are determined and discussed.

Ligand exchange reaction of sulfoxides in organic synthesis: a new method for one-carbon homologation of esters to carboxylic acids and esters via α-chloro α-sulfinyl ketones

Reaction of the Carbanion of chloromethyl phenyl sulfoxide with esters gave α-chloro α-sulfinyl ketones, which were treated with KH followed by t-BuLi to afford one-carbon homologated acids and esters in good to excellent yields.

Yellowjacket (Hymenoptera: Vespidae) Repellency by Natural Products of Paper Wasps and Avon's Skin-so-Soft©

Methyl palmitate and butyl palmitate, ant repellents first isolated from the sternal glands of paper wasps, were tested with a methyl ester homolog, methyl myristate, and Avon's Skin-So-Soft Bath Oil© against foraging German yellowjackets. Repellency remained high for six days for all compounds except methyl palmitate. Avon's Skin-So-Soft© was the most repellent. We suggest that this is due to two active ingredients, isopropyl palmitate and mineral oil.

ChemInform Abstract: Ester Homologation Revisited: A Reliable, Higher Yielding, and Better Understood Procedure.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ester homologation revisited: a reliable, higher yielding and better understood procedure

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEster homologation revisited: a reliable, higher yielding and better understood procedureConrad J. Kowalski and Rajarathnam E. ReddyCite this: J. Org. Chem. 1992, 57, 26, 7194–7208Publication Date (Print):December 1, 1992Publication History Published online1 May 2002Published inissue 1 December 1992https://doi.org/10.1021/jo00052a038RIGHTS & PERMISSIONSArticle Views1640Altmetric-Citations59LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Preparation and 1-carbon homologation of boronic ester substituted Δ 2-isoxazolines: The 1,3 dipolar cycloaddition of nitrile oxides to vinyl boronic esters

The dipolar cycloaddition of a variety of nitrile oxides to pinacol vinylboronate ( 2) is described. In addition, the 1-carbon homologation of the boronic ester substituted Δ 2-isoxazolines obtained from the cycloadditions has been carried out employing iodomethyllithium.

Organic synthesis: the roles of boron and silicon

Hydroboration reactions of organoboranes organoboron routes to unsaturated hydrocarbons allyl boranes and boron enolates boronic ester homologation properties of organosilicon compounds protection of alcohols as silyl ethers silyl enol ethers, silyl dienol ethers, silyl ketene acetals and 1,2-bis-siloxy alkenes alkene synthesis vinyl silanes allyl silanes.

Gas-liquid chromatography of esters of saturated fluorinated carboxylic acids

GLC has been used to determine the contribution of the methylene and difluoromethylene units to the sorption energy of the members of twelve homologous and pseudohomologous series of esters of n-polyfluorinated carboxylic acids for the SE-30 and SKTFT-50Kh stationary phases at 60–160‡C. An unusual increase in the energy of sorption of the methylene and difluoromethylene units with the increasing mass of the homolog has been observed. It has been found that, in distinction from the contributions of the methylene units, the sorption energy of the difluoromethylene units in the pseudohomologs is higher on the fluorinecontaining phase SKTFT-50Kh than on the nonpolar SE-30 phase, except the first unit. It has been shown that an increase in the temperature of the analysis reduces the energy contributions but that it has no influence on the general character of change of the sorption energy of the ester homologs and pseudohomologs.

Characterization of the surface composition of alkyl bonded phases under reversed-phase liquid chromatographic conditions using homologues of alkanoate and perfluoroalkanoate esters as solute probes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacterization of the surface composition of alkyl bonded phases under reversed-phase liquid chromatographic conditions using homologues of alkanoate and perfluoroalkanoate esters as solute probesR. K. Gilpin, M. Jaroniec, and S. LinCite this: Anal. Chem. 1990, 62, 19, 2092–2098Publication Date (Print):October 1, 1990Publication History Published online1 May 2002Published inissue 1 October 1990https://doi.org/10.1021/ac00218a009RIGHTS & PERMISSIONSArticle Views47Altmetric-Citations35LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (884 KB) Get e-Alerts Get e-Alerts

Transmembrane signaling during natural killer cell-mediated cytotoxicity. Regulation by protein kinase C activation.

NK cells can mediate either FcR-dependent cytotoxicity against antibody-coated target cells or direct cytotoxicity against a variety of tumor cells. We used homogeneous, cloned populations of CD16+/CD3- human NK cells to characterize and compare the transmembrane signaling mechanisms used during these alternative forms of cytotoxicity. Cross-linkage of NK cell FcR with anti-FcR (anti-CD16) mAb or direct binding to NK-sensitive tumor targets resulted in a rapid release of inositol phosphates and increases in [Ca2+]i. The receptor-dependent [Ca2+]i increase (as monitored in indo-1 loaded NK cells by flow cytometry) consisted of an initial release of calcium from intracellular stores, followed by a sustained influx of calcium across the plasma membrane. To assess the potential regulatory feedback role of protein kinase C (PKC) activation in these proximal signaling events, NK cells were pretreated with either PKC-activating phorbol esters, nonactivating phorbol ester homologs, or synthetic diacylglycerols. Brief pretreatment with activating phorbol esters rapidly inhibited, in a concentration-dependent manner, both phosphoinositide hydrolysis and increases in [Ca2+]i induced by FcR ligation, whereas pretreatment with an inactive phorbol ester had no effect. This acute inhibitory effect was not explained by FcR down-regulation, which occurred with more prolonged exposure to phorbol esters. In contrast, the phosphoinositide turnover and [Ca2+]i increase in NK cells stimulated with NK-sensitive tumor targets were not affected by prior exposure to PKC-activating phorbol esters. This differential regulatory effect of phorbol ester on proximal signaling was paralleled by a corresponding effect on cytotoxicity, i.e., phorbol ester-induced activation of PKC inhibited FcR-dependent cytotoxicity, but did not alter direct cytotoxicity against NK-sensitive tumor cells. These results indicate that PKC activation can differentially regulate alternative forms of NK cell-mediated cytotoxicity by rapidly and specifically desensitizing the FcR.

2,6-Di-O-pentyl-3-O-trifluoroacetyl cyclodextrin liquid stationary phases for capillary gas chromatographic separation of enantiomers

A series of liquid cyclodextrin derivatives, 2,6-di-O-pentyl-3-O-trifluoroacetyl α-, β- and γ-cyclodextrins (DP-TFA α-, β- and γ-CD), have been used as highly selective chiral stationary phases for capillary gas chromatography. More than 150 pairs of enantiomers were resolved; 120 on DP-TFA-γ-CD, which is the first reported γ-cyclodextrin stationary phase that is more widely useful than the β-cyclodextrin analogue. The enantiomers resolved include chiral alcohols, diols, polyols, amines, amino alcohols, halohydrocarbons, lactones, α-halocarboxylic acid esters, carbohydrates, epoxides, nicotine compounds, pyrans, furans and so on. Identical α values were observed for diol, amine and γ-halocarboxylic acid ester homologues, respectively. The relationship between the unusual selectivity behavior and separation mechanism is discussed.

Response of Aphid-Tending Ants to a Repellent Produced by Wasps (Hymenoptera: Formicidae, Vespidae)

Predation by ants on wasp brood is responsible for the evolution of an ant repellent produced by social wasps in the genus Polistes . The active component of the repellent, methyl palmitate, and its methyl ester homolog, methyl myristate, were tested against four ant species tending aphids. All four ant species were repelled, but the degree of repellency varied. Two hypotheses were tested to account for the differential repellency among ant species: repellency is a negative function of body size, and differences in social modes of foraging correlate with differences in repellency. The latter hypothesis was supported, in that ant species lacking plasticity in their foraging strategy and relying on trail odors are repelled much more extensively than ants using a variety of cues for locating food. It is hypothesized that wasps evolved their chemical defense in response to selection pressure from trail-following ants.

Tandem one-carbon homologation of esters to cyclopropanols

Esters react with diiodomethane in the presence of samarium to afford 1-substituted cyclopropanols in good yields.

Preparation of α-fluoro-α,β-unsaturated esters [formula omitted] two carbon homologation of esters

In the presence of diisobutyl aluminum hydride, esters react with an anion derived from (EtO) 2P(O)CFHC(O)OEt to give the title compounds in good yields. The scope of this method and the factors which influence the stereochemistry of the products are discussed.

Organoboranes: LI. Convenient procedures for the recovery of pinanediol in asymmetric synthesis via one-carbon homologation of boronic esters

Matteson's asymmetric synthesis via a one-carbon homologation of the pinanediol boronic esters with (dichloromethyl)lithium at −100°C results in the insertion of a chloromethyl group into the carboncarbon bond with > 99% diastereoselectivity. This procedure makes possible the asymmetric synthesis of the chiral moiety, RR′CH ★B(OR″) 2, providing an alternative route to chiral hydroboration for these valuable chiral intermediates. Unfortunately, this method suffers from the remarkable difficulty encountered in the recovery of the pinanediol chiral auxiliary, making this asymmetric synthesis impractical. Fortunately, a systematic study of the problem has uncovered convenient procedures for the recovery of pinanediol from pinanediol boronate esters.

High Temperature Decomposition of Military Specification L-23699 Synthetic Aircraft Lubricants

Previous investigations reported the formation of a neurotoxicant, tri methylolpropane phosphate (TMP-P) during pyrolysis of synthetic, aircraft engine lubricating oils. Employing both sealed-tube and open-to-air methods of pyrolysis, we confirmed the formation of TMP-P during lubricant pyrolysis. Rodent bioassay and GC/MS analysis were performed for detection and quanti tation of neurotoxicant production. Maximal production of TMP-P for sealed- tube pyrolysis occured after 20 min at 500°C. A comparable amount of TMP-P was formed after 5 min at 650°C in open-to-air pyrolysis of lubricants. Our examination of TMP-P production was limited to L-23699 lubricants composed primarily of a trimethylolpropane (TMP) ester base stock. The formation of TMP-P was only dependent upon the presence of an organic phosphorous addi tive and TMP. Pyrolysed lubricants composed of a pentaerythritol base did not cause neurotoxicity in mice or rats following intraperitoneal (i.p.) injection. Other toxic bicyclophosphorous ester homologues were not detected in any pyrolyzed lubricants following GC/MS analysis. L-23699 lubricants which had been operationally employed in aircraft engines under rigorous test conditions, produced no neurotoxicity when intraperitoneally administered to rats.

ChemInform Abstract: Molecular Design of Chiral Recognition Systems Based on Self Association‐Induced Non‐Equivalence.

In consideration of the flat-sheet structure known as a secondary structure of peptides and proteins, the self association of N-acyl α-amino acid derivatives may reasonably be expected to occur in non-aqueous media. To confirm the structure of dynamically formed molecular complexes, spectral studies of N-acetylvaline tert-butyl ester (1) in a carbon tetrachloride solution were carried out. A split of the amide NH resonance into two 1H nmr signals for the D and L enantiomers, termed self-induced non-equivalence, was observed when the solute was enantiomerically enriched in the solution. A concentration study of 1H and 13C-NMR showed the diastereomeric dimers, whose associative interactions are bidentate NH--O=C (ester) hydrogen bonds, to be in the enantiomeric solutions. Ir spectra confirmed the stability difference between the diastereomeric dimers by an external comparison of optically pure and racemic samples in the carbon tetrachloride solution.The association stereoselectivity of solute 1 was applied to the design of chromatographic phase systems. When racemic solute 1 is injected into a non-chiral silica gel column using mobile phase solvent containing chiral solute 1 as an additive component, the racemate should interact with chiral solute 1 added to the mobile phase solvent, while passing through the column, to form transient diastereomeric dimers as observed in solution, and be separated. Self association-induced resolution was confirmed experimentally using radiolabelled solute 1 and the radioactivity detection.Attempts were made to widen the scope of application involved in the hydrogen-bond association mode to chiral recognition through the development of other resolving agents. N-Acetylvaline tert-butylamide was found to separate the homologues of N-acyl α-amino acid esters. Tartaric esters and amides were found capable of separating a variety of enantiomeric compounds in non-aqueous media.

ChemInform Abstract: Irreversible Blockage of Opioid Receptor Types by Ester Homologues of β‐Funaltrexamine.

AbstractThe acid chlorides (IV), obtained from maleic anhydride (I) via the dicarboxylic acid monoesters (III), are coupled with 6β‐naltrexamine (V) to give the ester homologues (VIa) ‐ (VIe) of β‐funaltrexamine (VIf).

ChemInform Abstract: Organoboranes. Part 46. New Procedures for the Homologation of Boronic Esters: A Critical Examination of the Available Procedures to Achieve Convenient Homologation of Boronic Esters.

AbstractNine procedures using LiCHCl2 and LiCH2Cl are examined for the one‐carbon homologation of boronic esters.