Faced with globalization, high competition, and the demands of a market in constant dynamism, companies strive to adopt measures for increasing their productivity, among which Lean Manufacturing stands out. Although this set strategies allows optimizing production by reducing waste, literature review showed that, several organizations, implementation does not reflect positive impacts on productivity. It is frequently related superficial nature approach: tools methods are applied, but...

Abstract A microdispersive solid‐phase extraction method has been developed using multiwalled carbon nanotubes of 110–170 nm diameter and 5–9 μm length for the a group nine phthalic acid esters (i.e., bis(2‐methoxyethyl) phthalate, bis‐2‐ethoxyethyl dipropyl butylbenzyl bis‐2‐ n ‐butoxyethyl bis‐isopentyl bis‐ ‐pentyl dicyclohexyl di‐ ‐octyl phthalate) from tap water as well different beverages commercialized in plastic bottles (mineral water, lemon‐ apple‐flavored mineral an isotonic...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStereoselective syntheses of erythro- and threo-.beta.-amino alcohol derivatives via hetero-Diels-Alder reactionsM. Mark Midland Maria M. AfonsoCite this: J. Am. Chem. Soc. 1989, 111, 12, 4368–4371Publication Date (Print):June 1, 1989Publication History Published online1 May 2002Published inissue 1 June 1989https://pubs.acs.org/doi/10.1021/ja00194a033https://doi.org/10.1021/ja00194a033research-articleACS PublicationsRequest reuse permissionsArticle...

In this work, we have compared the selectivity of two commercial molecularly imprinted polymers (AFFINIMIP®SPE Estrogens and AFFINIMIP®SPE Zearalenone) for extraction 12 estrogenic compounds interest (i.e. 17α-estradiol, 17β-estradiol, estrone, hexestrol, 17α-ethynylestradiol, diethylstibestrol, dienestrol, zearalenone, α-zearalanol, β-zearalanol, α-zearalenol β-zearalenol) from different water samples. High-performance liquid chromatography coupled with ion trap mass spectrometry...

The reaction of vinyl allenes with imines under Lewis acid catalysis has been explored. Vinyl in which the allenic portion molecule is tri- or tetrasubstituted gave octahydroquinoline derivatives as single isomers together a minor compound formed by an ene imine allene. Compounds allene 1,3-disubstituted do not react conditions assayed.

An efficient method for conversion of ketones to their corresponding dimethyl and diethyl acetals cyclic β-diketones into β-keto enol ethers using Fe(OTs)3 as a catalyst is described.

In this work, the use of ionic liquid (IL) 1,3-dipentylimidazolium hexafluorophosphate ([PPIm][PF₆]) as an alternative extractant for IL dispersive liquid-liquid microextraction (IL-DLLME) a group pesticides and metabolites (2-aminobenzimidazole, carbendazim/benomyl, thiabendazole, fuberidazole, carbaryl, 1-naphthol, triazophos) from soils is described. After performing initial ultrasound-assisted extraction (USE), IL-DLLME procedure was applied these organic analytes soil extracts....

The hetero Diels−Alder reaction of vinyl allenes and aldehydes in the presence a Lewis acid has been studied both experimentally theoretically. Differently substituted were used to obtain information on structural requirements reaction. Theoretical calculations using density functional theory indicate that proceeds through highly asynchronous polar transition state.

A synthetic strategy for the preparation of trisusbstituted cyclic ethers is presented, in which stereochemistry at carbon atoms adjacent to oxygen ether was controlled by means a hetero Diels−Alder reaction between monoactivated diene and chiral aldehyde. The adducts were transformed into linear ethers, then used cis trans different sizes. cis-oxepane, cis-oxonane, cis-oxocane trans-oxocane prepared as examples scope strategy.

A formal synthesis of (+)- and (-)-laurecin has been accomplished, using a hetero Diels-Alder reaction between monoactivated diene (S)-(-)-2,3-O-isopropylidene-gylceraldehyde or its enantiomer as the key step.

The Lewis acid catalyzed hetero-Diels−Alder reaction between acyclic vinyl allenes and aldehydes as heterodienophiles was studied. This allows for the preparation of pyrane derivatives in good yields, high facial regioselectivity moderate endo/exo ratio. When benzaldehyde used heterodienophile, rearranged products were obtained depending on conditions. DFT calculations to study rearrangement, concluding that it is a highly selective ionic process, driven by stability products.

In this work, we studied carbon paste electrodes (CPEs) with two kinds of binders: mineral oil or ionic liquids (IL) derived from N-substituted octyl pyridinium bis(trifluoromethylsulfonyl)imide the substituents H-, CH3-, CN- and CF3-. The work aims to study series IL determine a possible effect substituent cation in behavior as binder graphite for obtaining IL-CPEs. electrochemical response electrical were measured by cyclic voltammetry impedance spectroscopy, respectively. Surprisingly,...

The application of nanotechnology has been an important tool in the development sustainable analytical procedures which have developed agreement with principles sustainability and green chemistry. In this sense, such materials widely applied area food analysis providing improvements terms specificity, efficiency, simplicity. Besides, recent years, discovery other innovative framework chemistry, as deep eutectic solvents (DESs), gained special attention from scientific community for whom...

New diterpenylquinones, combining a diterpene diacid and naphthoquinone, were prepared from junicedric acid lapachol. The new derivatives assessed as gastroprotective agents by the HCl-EtOH-induced gastric lesions model in mice well for basal cytotoxicity on following human cell lines: Normal lung fibroblasts (MRC-5), epithelial adenocarcinoma (AGS), hepatocellular carcinoma (Hep G2). Several of compounds significantly active antiulcer showed selective against AGS cells.