(S)-2-methyl-5-(prop-1-en-2-yl)cyclopent-1-ene-1-carbaldehyde (2) is a component of the essential oils of several plants and has also been used in many syntheses, usually of terpenes. Although the preparation of compound 2 has been reported several times, no side products have been reported previously. In this Short Note, we present the identification of one such side product. This new compound (3) arises from a vinylogous aldol autocondensation, occurring after the formation of 2, even when the reaction runs for a short time. However, it can diminish the yield of 2 when the reaction is allowed to continue for a longer time.

(R)-3,3,6-trimethyl-3,3a,4,5-tetrahydro-1H-cyclopenta[c]furan was obtained by the acid cyclization of the alcohol (S)-(2-methyl-5-(prop-1-en-2-yl)cyclopent-1-en-1-yl)methanol, which, in turn, is obtained from (R)-limonene. The structure of the new compound was established using NMR spectroscopy (1H, 13C, COSY, HSQC, and HMBC spectra) and high-resolution mass spectrometry. The chemical shifts of the proton and carbon atoms were calculated at the DFT level with a high correlation between the calculated and experimental values.

The 5,8-disubstituted indolizidines are the largest family of indolizidines isolated from the skin of amphibians. These compounds exhibit interesting biological activities such as noncompetitive blockers of nicotinic receptors. In this paper, we present a short, simple, and general synthesis of these alkaloids based on the hetero Diels–Alder reaction between suitable monoactivated dienes and Δ1-pyrroline as the dienophile. The selectivity of the process is explained based on computational studies. Concise synthesis of the indolizidine alkaloid 181B from a hetero Diels–Alder reaction was accomplished in four steps.

Research on the production of high-quality hydrogen is an important step to face the environmental problems caused by using fossil fuels. In this sense, water electrolysis appears as a good option to fulfil this need. However, the application of this technology at low-temperature ranges requires catalysts to carry out the reaction. Nowadays, commercial catalysts in basic media are mainly nickel-based materials, which are rapidly deactivated under operation conditions. This increases the price of H2 production. Therefore, new non-noble electrocatalyst materials are required to improve this feature. Current work describes the preparation and performance towards the hydrogen evolution reaction (HER) of various composite materials generated from powdered transition metal carbides (TMCs) and a pyridinium-based ionic liquid. Differential electrochemical mass spectrometry (DEMS) has been used to obtain an accurate measurement of the activity and to establish the kinetics of HER for the composite materials in NaOH 0.1 M media. The main results show that the ionic liquid acts as an inhibitor or promoter of oxide growth on the surface of the carbide depending on its nature. Because of this effect, there is an increase or decrease of the mean particle size of the material and, therefore, the catalytic performance towards HER is modified. So, it is concluded that the nature of the starting carbide is playing a central role in the interaction with the ionic liquid, changing the catalytic properties of the composite material.

A source of high-purity hydrogen is essential to overcome the problem of using fossil fuel consumption to obtain primary energy. Electrolysis of water arises as an important alternative to fulfil this necessity since it can be coupled to renewable sources and generates pure hydrogen. For this technology, low-temperature devices need new non-noble electrocatalyst materials that reduce its cost and perform with an acceptable activity and durability. In this sense, we present here the preparation and performance towards the hydrogen evolution reaction (HER) of several composite materials generated from hexagonal WC powder and different pyridinium-based ionic liquids. Differential electrochemical mass spectrometry (DEMS) is used to obtain not only an accurate measurement of the activity but also reliable information about kinetics and mechanism of HER on the surface of the studied materials in basic medium. Finally, it is proved that the presence of ionic liquids play an important role in the particle size distribution of the generated composite material and, therefore, in their capacitance, durability and catalytic activity.

The application of nanotechnology has been an important tool in the development of sustainable analytical procedures which have been developed in agreement with the principles of sustainability and green chemistry. In this sense, such materials have been widely applied in the area of food analysis providing important improvements in terms of specificity, efficiency, and simplicity. Besides, in recent years, the discovery of other innovative materials developed in the framework of green chemistry, such as deep eutectic solvents (DESs), has gained special attention from the scientific community for whom the design and successful application of sustainable strategies is a huge challenge. In this sense, the recent combination of nanomaterials and DESs have resulted in the performance of suitable approaches in the area of food sciences bringing about interesting alternatives in food analysis. The aim of this review article is to revise the application of nanomaterials combined with DESs in food analysis, paying special attention to the synthesis and characterization steps, as well as to the performance of the most recent approaches developed in the field for the analysis of food commodities.

Vinylallenes have been synthesized and used as reagents for many years. However, the number of reviews covering the advances in the chemistry of vinylallenes are scarce. Most of the information lies in general reviews about allenes or in reviews dedicated to specific areas of research. Today, vinylallenes are used in the synthesis due to the special characteristics of this moiety, a diene with a non-conjugated double bond and the capacity to generate axial chirality. In this review, the most relevant publications involving vinylallenes, published in the last fifteen years, are compiled. The review includes new or improved synthetic methods and the reactivity of vinylallenes prepared by classical or new methods. The reactions of vinylallenes have been classified as Nazarov-type processes, cycloaddition reactions, and reactions in which vinylallenes are key intermediates, usually non-isolated but essential for the process to occur. Other types of reactivity are also included.

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 with the substituents H-, CH3-, CN- and CF3-. The work aims to study this series of IL and determine a possible effect of the substituent of the cation in the behavior of the IL as a binder of graphite for obtaining IL-CPEs. The electrochemical response and the electrical behavior were measured by cyclic voltammetry and electrochemical impedance spectroscopy, respectively. Surprisingly, the substituent does not affect the cyclic voltammetry response because in all the cases, high resistance and high capacitive currents were obtained. The best response in terms of conductivity is obtained by CPE. In the case of impedance measurements, the substituent does not cause differences, and in all the cases, the IL-CPEs show nearly the same responses. CPE shows lower capacitance and higher resistance for diffusion compared to the IL-CPEs due to his lower porosity. The high resistance showed by the IL-CPEs by cyclic voltammetry can be attributed to poorly intermolecular forces among graphite, water, electrolyte, and ILs as demonstrated by theoretical calculations.

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 extraction of a group of nine phthalic acid esters (i.e., bis(2-methoxyethyl) phthalate, bis-2-ethoxyethyl phthalate, dipropyl phthalate, butylbenzyl phthalate, bis-2-n-butoxyethyl phthalate, bis-isopentyl phthalate, bis-n-pentyl phthalate, dicyclohexyl phthalate, and di-n-octyl phthalate) from tap water as well as from different beverages commercialized in plastic bottles (mineral water, lemon- and apple-flavored mineral water, and an isotonic drink). Determination was carried out by high-performance liquid chromatography coupled to mass spectrometry. The extraction procedure was optimized following a step-by-step approach, being the optimum extraction conditions: 50 mL of each sample at pH 6.0, 80 mg of sorbent, and 25 mL of acetonitrile as elution solvent. To validate the methodology, matrix-matched calibration and a recovery study were developed, obtaining determination coefficients >0.9906 and absolute recovery values between 70 and 117% (with relative standard deviations < 17%) in all cases. The limits of quantification of the method were between 0.173 and 1.45 μg/L. After the evaluation of the matrix effects, real samples were also analyzed, finding butylbenzyl phthalate in all samples (except in apple-flavored mineral water), though at concentrations below its limit of quantification of the method.

In this work, the suitability of Fe3O4 nanoparticles coated with reduced-graphene oxide as sorbent was evaluated for the extraction of a group of fourteen phthalic acid esters (i.e. benzylbutyl phthalate (BBP), bis-2-n-butoxyethyl phthalate (DBEP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dicyclohexyl phthalate (DCHP), bis-2-ethoxyethyl phthalate (DEEP), diisodecyl phthalate (DIDP), diisononyl phthalate (DINP), bis-isopentyl phthalate (DIPP), bis-(2-methoxyethyl) phthalate (DMEP), dimethyl phthalate (DMP), di-n-octyl phthalate (DNOP), bis-n-pentyl phthalate (DNPP), dipropyl phthalate (DPP)) from environmental samples. Extraction was carried out using magnetic-micro dispersive solid-phase extraction while separation, identification and quantification of the target analytes were achieved by ultra-high-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry. The methodology was validated for three different types of water samples using dibutyl phthalate-3,4,5,6-d(4) as internal standard for all of them. Recovery values ranged from 70 to 120% for the three matrices with relative standard deviation values lower than 20%. Limits of quantification of the method achieved were in the range 6-178 ng/L for all samples and analytes. The methodology was applied for the evaluation of real samples finding the presence of DMP, DPP, BBP, DIBP and DBP in some of the analysed matrices. (C) 2018 Elsevier B.V. All rights reserved.

This work shows the utility of the carbon dots, prepared from candle shoot, as promising candidates for nanothermometry devices based on temperature dependence of their emission lifetimes and of the changes of the full width at half maximum of the emission spectrum. The results indicate that both parameters show appreciable changes over the physiological temperature range (20–60°C).

In this work, we have compared the selectivity of two commercial molecularly imprinted polymers (AFFINIMIP®SPE Estrogens and AFFINIMIP®SPE Zearalenone) for the extraction of 12 estrogenic compounds of interest (i.e. 17α-estradiol, 17β-estradiol, estrone, hexestrol, 17α-ethynylestradiol, diethylstibestrol, dienestrol, zearalenone, α-zearalanol, β-zearalanol, α-zearalenol and β-zearalenol) from different water samples. High-performance liquid chromatography coupled with ion trap mass spectrometry with electrospray ionization was used for their determination. Results showed that although both molecularly imprinted polymeric cartridges were specifically designed for different groups of analytes (natural estrogens like estradiol in the first case and zearalenone derivatives in the second) they nearly have the same extraction performance (with recovery values in the range 65-101%) for the same analytes in Milli-Q water because of the cross-reactivity of the polymer. However, when more complex water samples were analyzed, it was clear that the behavior was different and that the AFFINIMIP®SPE Estrogens showed less cross-reactivity than the other cartridge. Validation of the proposed methodology with both cartridges revealed that the extraction was reproducible and that the final limits of detection of the proposed method were in the low ng/L range.

In this manuscript, a new method based on the use of off-line dispersive solid-phase extraction (dSPE) combined with ultra-high performance liquid chromatography with diode-array detection was developed to determine 11 sulfonamide antibiotics (sulfanilamide, sulfacetamide, sulfadiazine, sulfathiazole, sulfamerazine, sulfadimidin, sulfamethoxypyridazine, sulfadoxine, sulfamethoxazole, sulfisoxazole and sulfadimethoxine) in mineral waters with different mineral content. For this purpose, pristine multi-walled carbon nanotubes (MWCNTs) and magnetic-MWCNTs (m-MWCNTs) were used as sorbents. Magnetic nanoparticles were synthesized by means of a solvothermal process, assembled onto CNTs through an “aggregation wrap” mechanism and characterized by scanning electron microscopy. Parameters affecting the extraction such as volume and pH of the sample, amount of sorbent and type and volume of eluent were optimized. Once optimum extraction conditions (250mL of water at pH 6.0 and elution with 25mL of MeOH) were obtained, the extraction efficiency of the different carbon nanomaterials was compared. Results demonstrated the higher extraction capacity of pristine MWCNTs with recoveries between 61 and 110% (except for sulfacetamide which ranged between 40 and 53%) and between 22 and 77% for m-MWCNTs. Limits of detection lower than 32ng/L were achieved for all of the analyzed samples.

AbstractLewis acid mediated reaction of acyclic vinyl allenes and imines gives tetrahydropyridines with complete diastereoselectivity.

The Lewis acid mediated reaction of acyclic vinyl allenes and imines, yielding tetrahydropyridines has been carried out. Only one cycloadduct was observed in each case, and thus, the reaction progressed in all cases with total regio-, face- and endo/exo selectivities. The cycloadducts were transformed into polysubstituted pyridines, including bipyridines, by catalytic transfer hydrogenation using cyclohexene as hydrogen donor in good yield. The reaction was extended to the aromatization of the bicyclic cycloadducts prepared in previous works from the reaction of semicyclic vinyl allenes and imines, yielding tetrahydropyridines.

In this work, the use of the ionic liquid (IL) 1,3-dipentylimidazolium hexafluorophosphate ([PPIm][PF₆]) as an alternative extractant for IL dispersive liquid-liquid microextraction (IL-DLLME) of a group of pesticides and metabolites (2-aminobenzimidazole, carbendazim/benomyl, thiabendazole, fuberidazole, carbaryl, 1-naphthol, and triazophos) from soils is described. After performing an initial ultrasound-assisted extraction (USE), the IL-DLLME procedure was applied for the extraction of these organic analytes from soil extracts. Separation and quantification was achieved by high-performance liquid chromatography (HPLC) with fluorescence detection (FD). Calibration, precision, and accuracy of the described USE-IL-DLLME-HPLC-FD method using [PPIm][PF₆] as an alternative extractant was evaluated with two soils of different physicochemical properties. Accuracy percentages were in the range 93-118% with RSD values below 20%. A comparison of the performance of [PPIm][PF₆] versus that of the so-common 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIm][PF₆]) was accomplished. Results indicate a comparable extraction efficiency with both ILs, being slightly higher with [HMIm][PF₆] for the metabolite 2-aminobenzimidazole, and slightly higher with [PPIm][PF₆] for triazophos. In all cases, LODs were in the low ng/g range (0.02-14.2 ng/g for [HMIm][PF₆] and 0.02-60.5 ng/g for [PPIm][PF₆]). As a result, the current work constitutes a starting point for the use of the IL [PPIm][PF₆] for further analytical approaches.

In this work, a new method for the determination of eleven quinolone antibiotics (moxifloxacin, lomefloxacin, danofloxacin, ciprofloxacin, levofloxacin, marbofloxacin, enrofloxacin, difloxacin, pefloxacin, oxolinic acid and flumequine) in different water samples using dispersive solid-phase extraction (dSPE) and capillary zone electrophoresis with diode-array detection was developed. Oxidized multi-walled carbon nanotubes (o-MWCNTs) were used for the first time as stationary phases for the off-line preconcentration by dSPE of the antibiotics. A 65mM phosphate buffer at pH 8.5 was found adequate for analyte separation while large volume sample stacking with polarity switching of the analytes dissolved in water containing 10% (v/v) of acetonitrile was carried out in order to improve the sensitivity. dSPE parameters, such as sample volume and pH, o-MWCNT amount, volume and type of eluent in dSPE were optimized. Application of the developed method to the analysis of spiked Milli-Q, mineral, tap, and wastewater samples resulted in good recoveries values ranging from 62.3 to 116% with relative standard deviation values lower than 7.7% in all cases. Limits of detection were in the range of 28–94ng/L. The proposed method is very fast, simple, repeatable, accurate and highly selective.

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