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Abstract: In the last two decades, click chemistry has become a modular synthetic procedure to assemble new molecular structures. It is a powerful methodology that relies on the construction of carbon-heteroatom bonds of a variety of reactants. In modern synthetic chemistry, it has been applied in a large number of applications, from pharmaceutical to material science. The copper-catalyzed 1,2,3-triazole preparation, reacting organic azides with alkynes, has become the star of click chemistry due to its reliability and biocompatibility. As a consequence, this reaction has found many applications in diverse areas such as bioconjugation, material science, and drug discovery. In order to understand the effect of copper catalysts and ligands in click chemistry, it is important to understand the structural and mechanistic aspects involved. In this review, several physicochemical aspects of click chemistry are discussed. First, the mechanisms and intermediates involved in the preparation of 1,2,3-triazoles. Second, the different types of copper catalysts are used to perform the reaction regioselectively. The last section shows the structure and characteristics of effective ligands utilized to improve click chemistry under different experimental conditions.

Aims: Aims: Perform the synthesis of novel fluoro phenyl triazoles via click chemistry with or without microwave irradiation and their evaluation as anti-proliferative agents in SiHa cells background: Triazoles are heterocyclic compounds containing a five-member ring with two carbon and three nitrogen atoms. They are of great importance since many of them have shown to have important biological activity as antifungal, antiviral, antibacterial, anti-HIV, anti-tuberculosis, vasodilator, and anticancer agents. Background: Triazoles are heterocyclic compounds containing a five-member ring with two carbon and three nitrogen atoms. They are of great importance since many of them have shown to have biological activity as antifungal, antiviral, antibacterial, anti-HIV, anti-tuberculosis, vasodilator, and anticancer agents. Objective: Synthesize novel fluoro phenyl triazoles via click chemistry and evaluate their anti-proliferative activity Method: First, several fluorophenyl azides were prepared. Reacting these aryl azides with phenylacetylene in the presence of Cu(I) catalyst, the corresponding fluoro phenyl triazoles were obtained by two methodologies, stirring at room temperature and under microwave irradiation at 40 ºC. In addition, their antiproliferative activity was evaluated in cervical cancer SiHa cells Result: Fluoro phenyl triazoles were obtained within minutes by means of microwave irradiation. The compound 3f, containing two fluorine atoms next to the carbon connected to the triazole ring, was the most potent among the fluoro phenyl triazoles tested in this study. Interestingly, the addition of a fluorine atom to the phenyl triazole structure in a specific site increases its antiproliferative effect as compared to parent phenyl triazole 3a without a fluorine atom. Conclusion: Several fluoro phenyl triazoles were obtained by reacting fluoro phenyl azides with phenylacetylene in the presence of copper sulphate, sodium ascorbate and phenanthroline. Preparation of these triazoles with MW irradiation represents a better methodology since they are obtained within minutes and higher yields of cleaner compounds are obtained. In terms of biological studies, the proximity between fluorine atom and triazole ring increases its biological activity.

El objetivo de esta investigación es seleccionar los indicadores a utilizar en el proceso de evaluación del desempeño empresarial en las entidades del territorio holguinero (Cuba), que permitan la determinación de las causas que inciden en sus resultados. En el aspecto teórico se empleó el análisis-síntesis; para el procesamiento de la información, el método inductivo-deductivo, en el caso de la determinación de las causas más representativas que influyen en el desempeño empresarial de las entidades del territorio holguinero. Dentro de los métodos empíricos se encuentra la encuesta, observación directa y lista de chequeos. Como resultado principal, se seleccionaron los indicadores que facilitan la evaluación del desempeño empresarial en entidades del territorio holguinero. Esta selección permitió su reducción en un 55 % (cuarenta y cinco indicadores a veinticinco); agrupados de la siguiente forma: gestión, técnico organizativos, organización de los procesos y económicos-financieros. Este análisis se efectuó a partir de las experiencias empíricas en el territorio holguinero y la valoración teórica de un grupo de expertos de la academia. Los resultados evidencian que durante el periodo 2010–2019, no se logró un óptimo desempeño empresarial, fundamentalmente por factores relacionados con los recursos materiales y los medios de trabajo.

Background: The complex photochemistry of aryl azides has fascinated scientists for several decades. Spectroscopists have investigated the intermediates formed by different analytical techniques. Theoretical chemists have explained the intrinsic interplay of intermediates under different experimental conditions. Objective & Method: A complete understanding of the photochemistry of a given fluoro aryl azide is a basic requisite for its use in chemistry. In this review, we will discuss the synthesis of several fluoro substituted aryl azides and the reactions and intermediates generated upon photolysis and thermolysis of these azides and some examples of their applications in photoaffinity labeling and organic synthesis. Conclusion: In spite of the extensive research on the photochemistry of fluoro aryl azides, there are some areas that remain to be investigated. The application of this reaction in the synthesis of novel heterocyclic compounds has not been fully studied. Since fluorophenyl azides are known to undergo C-H and N-H insertion reactions, they could be used to prepare new fluorinated molecules or in the biochemical process known as photoaffinity labeling.

Diclofenac (DCF) photocatalytic degradation with TiO2-P25 illuminated with UV-A light in aqueous media was investigated. The photodegradation rate was assessed by HPLC and UV–vis spectroscopy, while the mineralization rate was obtained by total organic carbon measurements. The formation and degradation of intermediate compounds were investigated by UV–vis, IR and 1H NMR spectroscopy and GC/MS analysis. UV–vis absorbance and HPLC results indicated that DCF is completely transformed into some aromatic compounds after several hours of irradiation. TOC analysis indicated that some intermediate compounds are degraded slowly since 90% mineralization was achieved after several hours of irradiation. FT-IR studies demonstrated a rapid conversion of diclofenac into a lactam, which was converted into several aromatic compounds. GC/MS and HPLC analysis indicated that the initial photoproducts are two lactams and several aromatic anilines and phenols. 1H NMR studies indicated DCF degrades by a rather simple mechanism generating a recalcitrant intermediate acid, namely 2-hydrophenyl acetic acid which is oxidized in several steps by hydroxyl radicals. 1H NMR studies also indicated that an oxidation route via a quinone is actually a very minor pathway. Based on this and previous investigations, a total photocatalytic degradation mechanism for DCF is presented, first involving hydroxyl radical reactions to generate anilines and phenols, which were all converted into polyhydroxylated compounds and eventually into low molecular saturated and unsaturated amines and carboxylic acids. Basic studies about diclofenac photocatalytic degradation are required for future applications of this process in the removal of DCF and other structurally related pharmaceutical compounds from any water body.

Background:Molecular organic photochemistry is concerned with the description of physical and chemical processes generated upon the absorption of photons by organic molecules. Recently, it has become an important part of many areas of science: chemistry, biology, biochemistry, medicine, biophysics, material science, analytical chemistry, among others. Many synthetic chemists are using photochemical reactions in crystals to generate different types of organic compounds since this methodology represents a green chemistry approach.Objective & Method:Chemical reactions in crystals are quite different from reactions in solution. The range of organic solid state reactions and the degree of control which could be achieved under these conditions are quite wider and subtle. Therefore, for a large number of molecular crystals, the photochemical outcome is not the expected product based on topochemical principles. To explain these experimental results, several physicochemical factors in crystal structure have been proposed such as defects, reaction cavity, dynamic preformation or photoinduced lattice instability and steric compression control. In addition, several crystal engineering strategies have been developed to bring molecules into adequate orientations with reactive groups in good proximity to synthesize complex molecules that in many cases are not available by conventional methods. Some strategies involve structural modifications like intramolecular substitution with different functional groups to modify intermolecular interactions. Other strategies involve chemical techniques such as mixed crystal formation, charge transfer complexes, ionic and organometallic interactions. Furthermore, some examples of the single crystal to single crystal transformations have also been developed showing an elegant method to achieve regio and stereoselectivity in a photochemical reaction.Conclusion:The several examples given in this review paper have shown the wide scope of photochemical reactions in organic molecular crystals. There are several advantages of carrying photochemical reaction in the solid state. Production of materials unobtainable by the traditional solution phase reactions, improved specificity, reduction of impurities, and enhancement in the yields by the reduction of side reactions. These advantages and the multidisciplinary nature of solid-state photochemistry make this discipline quite likely to develop a lot in the future.

Pyridofuroxans are analogous to benzofuroxans; they present similar properties and may be synthesized in similar ways. However, when they are prepared from o-nitropyridinazides, they do not need energy to be synthesized, in contrast to benzofuroxans which require heat or light. In order to understand this phenomenon, a DFT study about the mechanism of pyridofuroxan formation from a series of substituted o-nitropyridinazides (2-azido-3-nitropyridines) was performed. The results suggest that spontaneous formation of pyridofuroxans at room temperature is possible when o-nitropyridinazide is protonated at the pyridinic nitrogen.

Anilino and indolo quinones have emerged as important structural motifs and medicinal targets since they are often crucial for expression of interesting biological properties. The synthesis of anilino quinones could be achieved by means of different methodologies. Performing this reaction under reflux without a catalyst takes several days. Under this conventional heating, the use of different catalysts reduces the time to hours. Two strong Lewis acids with good oxidation properties, such as CeCl3 and FeCl3, accelerate two important steps: first, the formation of a complex; and then the final oxidation and regeneration of the quinone. In the same manner, a combination of a Bronsted acid and a good oxidant, Cu(OAc)2 in acetic acid, has a catalytic effect. The synthesis of anilino quinone derivatives under conventional reflux and a catalyst was compared with the synthesis using microwave (MW) or ultrasound (US). Under these alternative sources of energy, the procedures are faster and the reactions become regioselective with the formation of crystalline compounds. In some cases, the products obtained do not require chromatographic purification. In addition, since the reactions are performed under a homogeneous temperature, alternative and more selective mechanisms can operate. For example, with us heating, a low energy EDA mechanism is favored in the reaction of anilines with naphthoquinone. In this case, performing N-arylation reactions with FeCl3 in ethanol results in decomposition of compounds. Better results are obtained in aqueous ethanol where the mixture of solvents dissipates the heat better. In the synthesis of indolo quinone derivatives, both alternative sources of energy accelerate the reactions. The yields are not increased, but the products are cleaner with less amounts of secondary products.

The photocatalytic oxidation of diclofenac, which is a non-steroidal anti-inflammatory medication, with TiO2 illuminated with UV-A light under constant flow of pure oxygen has been investigated in our laboratories to evaluate the effect of initial reactant concentration on the reaction rate. Diclofenac adsorption experiments under dark conditions were also carried out to get information about the interaction between the organic molecule and the solid catalyst. Adsorption experiments at natural pH under dark conditions confirmed that the negatively charged diclofenac molecule is easily adsorbed on the positively charged surface of titania reaching equilibrium in less than 50 min. According to the Langmuir isotherm, the adsorption constant (Keq) and the maximum uptake of diclofenac (qm) on the surface of commercial TiO2 are 21.1401 L mMol−1DFC and 0.04013 mMoles DFC g−1 TiO2, respectively. Experimental results also indicate that the initial reaction rate of the photocatalytic degradation of diclofenac obeys the Langmuir–Hinshelwood–Hougen–Watson model with a kinetic constant K1 = 0.08489 min−1 and an adsorption parameter K2 = 14.12821 mM−1L. Combined chemical analysis of the reaction samples by HPLC, TOC, and UV–vis spectroscopy indicated that the diclofenac is efficiently mineralized by photocatalysis via hydroxylation of the aromatic rings to form 2-aminophenol, catechol, benzene-triol, 2,6-dichloroaniline, and fumaric acid, which in turn are completely mineralized to CO2 and water.

The photodegradation of the proton pump inhibitor omeprazole (OME) in aqueous media with the system UV/O is presented. The photodegradation rate was assessed by HPLC and UV-vis spectroscopy, while the mineralization rate was obtained by TOC measurements. Degradation products were investigated by IR spectroscopy and GC-MS analysis. UV-vis absorbance and HPLC results indicated that OME is completely degraded within 3 minutes of irradiation. TOC analysis indicated that intermediates compounds are relatively easy to mineralize since 80% mineralization is achieved within 2 hours. IR studies demonstrated a rapid oxidation of OME leading to the formation of amines and both sulfonic and carboxylic acids. GC-MS data indicated that the initial photoproducts are derivatives of both benzimidazole and pyridine produced after the photochemical cleavage of the C–S bond. Plausible mechanisms for the direct and indirect degradation of OME are given. In the photochemical degradation of OME, many intermediate compounds are actually generated. Several of them were generated from hydroxyl radical reactions, but some of them resulted from rearrangements, reductive reactions, and through the formation of highly reactive intermediates such as pseudo carbene, thiooxirane, and sulfenamide. 2

The host–guest inclusion complex structure and binding ability of two different quinolones with γ-cyclodextrin (γ-CD) were investigated in solution by means of UV–Vis and 1H NMR spectroscopy. Competition of oxolinic and nalidixic acid molecules for the γ-CD cavity was evaluated by determination of association constants. Both quinolones form 1:1 inclusion complexes, their binding constants at room temperature (25 °C) under acidic and basic conditions were calculated using Benesi–Hildebrand equation. The stability of the complexes was dependent on the structure of the quinolone. In general, the weaker binding constants were observed for oxolinic acid-γ-CD complexes (1616 and 1765 M−1) and the larger binding constants were obtained for nalidixic acid-γ-CD complexes (3760 and 3840 M−1). 1H NMR studies in D2O were performed to elucidate the structure of each inclusion complex, nalidixic acid molecule penetrates more deeply into the γ-CD cavity and an intermolecular hydrogen bond is formed. Knowledge about structure and relative stability of quinolone-γ-CD complexes will be useful for future applications of these antimicrobial agents in medicinal chemistry.

Background: In recent years, there has been a growing interest in the environmental relevance of the presence of several pharmaceutical compounds and their metabolites in water. To avoid further accumulation of these compounds and their metabolites in the aquatic environment, several research groups are investigating chemical and photochemical methods that could be applied in their destruction and subsequent removal from natural and wastewater. Objective & Method: Different chemical advanced oxidation processes are being developed to destroy organic pollutants in water. Most of these methods are based on the production of HO• radicals that are known to be highly reactive and strong oxidizing agents. In aqueous chemical processes, these radicals can be generated using a variety of reagents and under different reaction conditions such as O , H O /UV, TiO /UV, O /UV, H O /Fe , H O /Fe /UV and O /Fe /Cu /UV. This review is a survey on recent advances in the application of different chemical advanced oxidation processes to mineralize pharmaceuticals. Paracetamol was selected as a model compound since its structure is the main component or metabolite of several anesthetic and analgesic compounds. The degradation of paracetamol by different advanced oxidation methods has been investigated by a combination of techniques (TOC, UV-Vis, IR, HPLC and GC-MS) in order to determine the optimal reaction conditions, kinetics, intermediate and product compounds generated. Conclusion: Understanding the basic concepts about reaction conditions, intermediates and mechanistic details on mineralization of paracetamol will be quite useful for future applications of several techniques in the removal of this and other structurally related pharmaceutical and aromatic compounds from water. 3 2 2 2 3 2 2 2 2 3 2+ 2+ 2+ 2+

Genetically modified (GM) maize has been grown and safely consumed on a global scale since its commercialization in 1996. However, questions have been raised about the potential impact that GM maize could have on native maize landraces in Mexico, which is the center of origin and diversity of maize. This research was conducted to evaluate potential changes to maize landraces in an unlikely event of transgene introgression. For this study, two GM traits that confer insect protection and herbicide tolerance in maize (MON 89034 and MON 88017), designated as VT3Pro, were introgressed into two Mexican landraces, Tuxpeño and Tabloncillo. Field trials were conducted across four environments to assess phenotypic characteristics, plant response to stressors, and kernel composition of landraces with and without VT3Pro traits. Furthermore, materials from four backcrossing generations were analyzed for segregation of these GM traits. Generally, no significant differences were observed between landraces with and without VT3Pro traits for the evaluated characteristics and the segregation analysis showed that GM traits, when introgressed into landraces, followed Mendelian principles. These results support the conclusion that, if inadvertently introgressed into landraces, VT3Pro traits are not expected to alter phenotypic or kernel characteristics, plant response to stressors (except for targeted insect protection and herbicide tolerance traits) and would segregate like any endogenous gene. These results should be taken into consideration when discussing benefits and risks associated with commercial production of GM maize hybrids in the centers of origin and diversity of maize. Electronic supplementary material The online version of this article (10.1007/s11248-019-00160-3) contains supplementary material, which is available to authorized users.

The photocatalytic degradation of β-blockers in TiO2 was investigated. Metoprolol (MET) was selected as a model compound since its structure is quite similar to several compounds utilized as β-blockers. MET degradation as a function of time was investigated by means of several analytical techniques. Analyzing the degradation mixtures by total organic carbon (TOC) analyzer and high-performance liquid chromatography (HPLC), it was evident that after one hour of irradiation, MET was transformed into other more recalcitrant intermediates. Latter intermediates were slowly degraded achieving 80% mineralization after four hours of irradiation. Gas chromatography – mass spectrometry (GC–MS) analysis of mixtures obtained upon irradiation at short reaction times (an hour or less) allowed the identification of several new intermediate organic compounds. Among those, several aromatic and low molecular weight amines. Polyhydroxylated compounds were also identified but only in trace amounts. Infrared (IR) and ultraviolet-visible (UV–vis) spectroscopy studies indicated that MET is first transformed into several hydroxylated aromatic compounds. Eventually, after several hours of irradiation, these compounds are transformed into low molecular weight unsaturated acids. HPLC analysis of reaction mixtures and coinjection of standard solutions allowed the detection of several intermediates, namely 1,4-hydroquinone, 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol, 4-hydroxybenzandehyde, 1,2,4-benzenetriol, catechol and oxalic acid. Nuclear magnetic resonance (NMR) studies in deuterated solvents allowed the unequivocal detection of some of the aromatics in the reaction mixture. These NMR studies also demonstrated the transformation of aromatics into low molecular alkenes and acids. MET degradation routes and a detailed reaction mechanism is presented based on the intermediates identified. Fundamental aspects about MET degradation will be quite useful for future applications of photocatalysis in the degradation of other β-blockers, pharmaceuticals and organic compounds with structures similar to MET.

Several synthetic and natural naphthoquinone derivatives have been associated with antifungal activity. Candida albicans is a fungus that is known to exist in the normal human flora, but under certain conditions it can cause mild to fatal infections. Its pathogenicity has been associated with fungus conversion from cellular yeast to filamentous form Y–M. Inhibition of this process by several anilino-, dianilino-, phenoxy-, and diphenoxy-1,4-naphthoquinones was investigated in order to find some correlation between structure, redox properties and biological activity.

Pyridofuroxans present ring-chain tautomerism in analogy with benzofuroxans. In this work we used density functional theory to evaluate the tautomerism in a series of substituted pyridofuroxans and propose a mechanism. The studied substituents are 7-hydroxi, 7-amino, 7-methyl, and 6-bromine; we also studied 4-protonated pyridofuroxan. For all studied pyridofuroxans, calculations suggest three dinitroso intermediate conformers involved in the tautomerism and an energy barrier high enough to avoid tautomerization at room temperature.

High purity metoprolol prepared by neutralization of an aqueous solution of metoprolol tartrate is efficiently mineralized to CO2 and water by photocatalysis with TiO2, UV light and a constant flow rate of oxygen. Since the tartrate anions were eliminated, all the HO• generated by photocatalysis reacted efficiently with the aromatic part of the medication. The reaction pathway includes two routes of degradation. The first one includes the transformation of metoprolol to hydroquinone via formation of 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde. Metoprolol is also degraded directly to hydroquinone. Then, this aromatic compound is oxidized to 1,2,4-benzenetriol, which is rapidly oxidized to low molecular weight organic acids before being completely mineralized to CO2 and water. Kinetic studies indicated that the initial reaction rate of the degradation of metoprolol, 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde is described by the LH-HW model.

2-chloro-3-(R-anilino)-1,4-naphthoquinones react with sodium azide upon refluxing in DMF. The thermochemistry of 2-azido-3-(R-anilino)-1,4-naphthoquinone is strongly modified by the substituent on aniline. Having an strong electron-donor like O-R results in the generation of a phenazine while having an electron-withdrawing substituent results in the formation of 2-amino-3-(R-anilino)-1,4-naphthoquinone. The products obtained are explained in terms of singlet and/or triplet nitrene chemistry.

The photocatalytic degradation of BPA aqueous solutions with commercial TiO2 (Evonik P25) was carried out in a home-made batch reactor illuminated with four UV lamps (λmax= 365 nm) in order to determine the kinetic parameters of the reaction rate equation and to identify and quantify some of the most stable aromatic intermediate reaction products. Low concentration (20 ppm) BPA solutions were completely degraded and mineralized in less than three hours of reaction. Whereas, BPA aqueous solutions with concentration above 50 ppm are transformed in other chemical compounds in 6 hours of reaction and fully mineralized in 15 hours of reaction. Kinetic analysis of the experimental results of BPA concentration as a function of time indicated that this photocatalytic degradation process follows a LH-HW reaction rate law where the reaction order shift from zero order to first order as the reactant concentration is decreased. Analysis of the reaction samples by different analytical techniques indicated that BPA is mineralized via formation of hydroquinone, benzoquinone, benzene-triol, catechol, and phenol by two simultaneous reaction pathways.

Several novel 2-(fluoroanilino)-3-(2,4-dinitroanilino) derivatives of 1,4-naphthoquinone have been synthesized in good to excellent yields. First, 2-chloro-3-(2,4-dinitroanilino)-1,4-naphthoquinone was prepared in two steps beginning with the reaction of 2,3-dichloro-1,4-naphthoquinone with aniline in the presence of a Lewis acid (CeCl ·7H O). The resulting 2-(anilino)-1,4-naphthoquinone was then nitrated. The strong electron withdrawing effect of the 2,4-dinitroanilino substituent on the naphthoquinone framework facilitated the displacement of the second chlorine atom by a variety of weakly nucleophilic fluoro-substituted anilines under reflux conditions. 3 2

Soybean agglutinin (SBA) protein, also known as soybean lectin, is regarded as an anti-nutrient due to its negative effect on the ability of monogastric animals to gain weight following consumption of raw soybean seed. Historically, SBA has been measured using a time-consuming and cumbersome hemagglutination procedure. The objective of our research was to obtain a validated methodology that is precise and accurate in the measurement of SBA while allowing minimally equipped laboratories to effectively conduct the analysis, thus our focus was on evaluating an existing commercially available ELISA, an enzyme-linked-lectin-assay (ELLA), and a hybrid ELISA/ELLA. A new ELLA technique that can detect and quantify lectins was chosen and modified specifically for the quantitation of SBA in soybean seed. The proposed ELLA methodology is similar to a standard sandwich ELISA, and uses polyacrylamide-linked N-acetylgalactosamine (Gal–NAc–PAA) for a capture phase and the biotinylated version (Gal–NAc–PAA–Biotin) for detection. Based upon the validation data, the ELLA method can precisely and accurately determine soybean lectin levels in soybean seed. The validated ELLA method was used to quantify SBA in nine commercial soybean varieties introduced between 1972 and 2008 and demonstrated that the natural variability of SBA is subject to the effects of genotype and environment.

El bienestar económico de las organizaciones es un aspecto vinculado con la Administración de Operaciones (AO) y que generalmente se identifica a través de las Funciones de la Administraciónde Operaciones (FAO). De estas se conoce que han sido ampliamente tratadas en la literatura, aunque de forma muy escasa, enel sector de los servicios y no siempre se ha logrado su análisis de forma integrada. El sector empresarial cubano no se encuentra ajeno a esta realidad, y aunque se reconoce lo alcanzado, existe una intención de mantenerlo y perfeccionarlo, por lo que constituye una prioridad para la dirección del país el perfeccionamiento de la AO dentro de su sistema empresarial. Atendiendo a lo anterior se desarrolló un procedimiento que permite el perfeccionamiento de las funciones de la administración de operaciones. Este ha sido aplicado en varias entidades de servicios, mostrando diversos resultados que se observan en este artículo.

Naphthoquinone amino derivatives exhibit interesting physicochemical properties and a wide range of biological activities with potential medicinal applications. A clean, fast and simple method for the preparation of phenylamino-1,4-naphthoquinones is presented by the reaction of naphthoquinone (NQ) and anilines under ultrasound irradiation (US). Anilino derivatives were synthesized in good yields and shorter reaction times in comparison with the conventional method. This ultrasound procedure can be applied to the preparation of naphthoquinone derivatives with anilines containing electron-donor substituents (2-OMe, 4-OMe, 4-Me and 4-OEt) or halogen or electron-withdrawing substituents (4-F, 4-Cl, 4-Br, 3-F, 3-Cl, 3-Br, 4-Ac). This procedure was also applied to the reaction of anilines with 2,3-dichloro-1,4-naphthoquinone (DCNQ). A reaction mechanism involving an EDA complex is proposed based on NMR experiments and previous studies about solid/solid reactions.

Naphthoquinone amino derivatives exhibit interesting physicochemical properties and are of interest for potential medicinal purposes. The preparation of novel 2-(nitrophenylamino)-1,4-naphthoquinones derivatives was achieved by reaction of nitroanilines with 1,4-naphthoquinone with a catalytic amount of FeCl 3 or by direct nitration of 2-(phenylamino)-1,4-naphthoquinone (PAN). Structural and photophysical properties of a series of NO 2 PANs and FPANs derivatives are examined using computational and spectroscopic methods. Absorbance and emission spectra are measured in a range of solvent environments to examine the impact of solvent–solute interactions. Additionally quantum calculations are used to evaluate the electronic nature of the spectral transitions and compare structures of the different PAN derivatives. The lowest energy electronic transitions have charge transfer character, and show the most sensitivity to solvent and substituents. Higher energy π–π * transitions are relatively insensitive to both factors. Computational predictions are in good agreement with the experimental spectra, and provide molecular-level insight variations amongst the different aniline-substituents.

The reaction of sodium azide with perfluorobenzene, containing an electron-withdrawing group, under microwave irradiation results in the fast preparation of p-substituted tetrafluorophenyl monoazides. Having an excess of sodium azide and a strong electron-withdrawing group like NO2 or CN, fluorophenyl diazides are also produced upon conventional or microwave heating. A synergic effect between the amount of sodium azide and the electron-withdrawing character of the substituents is observed giving different products. A discussion on the products and reaction mechanism is presented.

The advanced oxidation of high purity metoprolol tartrate, extracted from a commercial medicament, with TiO2 and UV light (365 nm) was investigated to determine the effect of initial reactant concentration on the reaction rate and the role of direct photolysis on the photocatalytic process. Analysis of the reaction samples by UV–Vis spectroscopy indicated that metoprolol tartrate is efficiently degraded by photocatalysis via hydroxylation of the aromatic ring. Kinetic studies indicated that the photocatalytic degradation of metoprolol tartrate follows a Langmuir, Hinshelwood, Hougen and Watson (LHHW) mechanism where the reaction order shifts from zero order to first order as the reactant concentration drops. Additional experiments showed that direct photolysis plays a minor role on the photocatalytic oxidation of metoprolol tartrate. Total organic carbon (TOC) studies demonstrated that metoprolol tartrate is transformed to other organic intermediate reaction products before complete mineralization to CO2. The fraction of reactant transformed into intermediate organic products was evaluated by a material balance using the results of analysis of the reaction samples by high performance liquid chromatography and TOC.

Density functional calculations at the BP86/6-311G(d,p) level of theory were realized to analyze the existence of intramolecular hydrogen bonds in a series of neutral 2-anilinonaphthoquinones. The ortho position of the aniline ring (C 2a ) was unsubstituted in two of them, substituted by a fluorine atom in another two compounds, and substituted by a methoxy group in an additional pair of compounds. The characteristic features of hydrogen bond formation (elongation of O C 1 , N H, F C 2a and O C 2a bonds, increase in the out-of-plane N H bending frequency, decrease in the N H stretching frequency) suggest the formation of a regular (two-center) intramolecular hydrogen bond in 2-anilinonaphtoquinones, involving nitrogen as donor and an oxygen in the naphtoquinone fragment as acceptor. The geometry and frequency changes also suggest the formation of a second and weaker hydrogen bond, resembling a bifurcated (three-center) intramolecular hydrogen bond, in fluorine- or methoxy- ortho -substituted 2-anilinonaphtoquinones.

2,4-Dichlorophenol (2,4-DCP) is considered a priority pollutant due to its high toxicity. Therefore, it is urgent to develop technologies for the disposal of this pollutant. Various remediation processes have been proposed for the elimination of 2,4-DCP in contaminated water, however, most of them involve high costs of operation and maintenance. This study aimed to determine the capacity of remediation of 2,4-DCP in water by Typha latifolia L. wild plants. For that, the tolerance, removal, accumulation and biotransformation of 2,4-DCP by T. latifolia were investigated. The plants were exposed to 2,4-DCP solutions with a concentration range from 1.5 to 300 mgL −1 for 10 days. They exhibited a reduction in chlorophyll levels and growth rate when 2,4-DCP solutions were ≥30 mgL −1 and ≥50 mgL −1 , respectively. The removal of contaminant was dose-depended, being 99.7% at 1.5–3 mgL −1 , 59–70% at 10–70 mgL −1 and 35–42% at 100–300 mgL −1 of 2,4-DCP in the solution. Studies indicated that 2,4-DCP was mainly accumulated in root tissue rather than in shoot tissue. Acid hydrolysis of biomass extracts suggests 2,4-DCP bioconjugates formation in root tissue as a response mechanism. Additionally, an increment in glutathione S-transferase (GST) activity could indicate a 2,4-DCP conjugation with glutathione as a detoxification mechanism of T. latifolia.

The strong electron withdrawing nature of the 2,4-dinitroanilines in substrate (I) allows the displacement of chlorine by weak nucleophilic anilines to give the title products (III).

Reaction of o-halonitrobenzenes with sodium azide under reflux of DMF/H2O gives benzofuroxans in one step in moderate to good yields. This is a faster methodology compared to the conventional procedure involving the preparation and subsequent pyrolysis of o-nitrophenyl azides. For comparison, the reaction was also performed under phase-transfer catalysis.

The advanced oxidation of paracetamol (PAM) promoted by TiO(2)/UV system in aqueous medium was investigated. Monitoring this reaction by HPLC and TOC, it was demonstrated that while oxidation of paracetamol is quite efficient under these conditions, its mineralization is not complete. HPLC indicated the formation of hydroquinone, benzoquinone, p-aminophenol and p-nitrophenol in the reaction mixtures. Further evidence of p-nitrophenol formation was obtained following the reaction by UV-vis spectroscopy. Continuous monitoring by IR spectroscopy demonstrated the breaking of the aromatic amide present in PAM and subsequent formation of several aromatic intermediate compounds such as p-aminophenol and p-nitrophenol. These aromatic compounds were eventually converted into trans-unsaturated carboxylic acids. Based on these experimental results, an alternative deacylation mechanism for the photocatalytic oxidation of paracetamol is proposed. Our studies also demonstrated IR spectroscopy to be a useful technique to investigate oxidative mechanisms of pharmaceutical compounds.

Pyrostegia venusta (Ker Gawl.) Miers is used in traditional medicine for the treatment of vitiligo, dysentery, immoderate menstrual flow, common diseases of the respiratory system, and for the treatment of genital infections. This work describes the effect of different explants, media components, and antioxidants on callus development from P. venusta. The effect of osmotic and water stress on flavonoids and sterols content was also evaluated. Best callus formation was obtained when leaves were used as explants and employing Murashige and Skoog medium with 2,4-dichlorophenoxiacetic acid (1 mg l−1), benzyladenine (0.1 mg l−1), and 4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid (1 mg l−1). Addition of cooper increase development of callus and the mixture of ascorbic acid, citric acid, and polyvinyl pyrrolidone reduced oxidation significantly. Water stress increased 4.6 folds the content of sterols, while osmotic stress induced 3.8 and 2.2 folds sterols and flavonoids concentration, respectively, in relation to leaves. The results suggest that P. venusta callus could be a novel source of bio-compounds for pharmaceutical preparations.

One of the major constraints facing the large-scale production of cassava (Manihot esculenta) roots is the rapid postharvest physiological deterioration (PPD) that occurs within 72 h following harvest. One of the earliest recognized biochemical events during the initiation of PPD is a rapid burst of reactive oxygen species (ROS) accumulation. We have investigated the source of this oxidative burst to identify possible strategies to limit its extent and to extend cassava root shelf life. We provide evidence for a causal link between cyanogenesis and the onset of the oxidative burst that triggers PPD. By measuring ROS accumulation in transgenic low-cyanogen plants with and without cyanide complementation, we show that PPD is cyanide dependent, presumably resulting from a cyanide-dependent inhibition of respiration. To reduce cyanide-dependent ROS production in cassava root mitochondria, we generated transgenic plants expressing a codon-optimized Arabidopsis (Arabidopsis thaliana) mitochondrial alternative oxidase gene (AOX1A). Unlike cytochrome c oxidase, AOX is cyanide insensitive. Transgenic plants overexpressing AOX exhibited over a 10-fold reduction in ROS accumulation compared with wild-type plants. The reduction in ROS accumulation was associated with a delayed onset of PPD by 14 to 21 d after harvest of greenhouse-grown plants. The delay in PPD in transgenic plants was also observed under field conditions, but with a root biomass yield loss in the highest AOX-expressing lines. These data reveal a mechanism for PPD in cassava based on cyanide-induced oxidative stress as well as PPD control strategies involving inhibition of ROS production or its sequestration.

Over two hundred and fifty million Africans rely on the starchy root crop cassava (Manihot esculenta) as their primary source of calories. Cassava roots, however, have the lowest protein:energy ratio of all the world's major staple crops. Furthermore, a typical cassava-based diet provides less than 10-20% of the required amounts of iron, zinc, vitamin A and vitamin E. The BioCassava Plus program employed modern biotechnologies to improve the health of Africans through development and delivery of novel cassava germplasm with increased nutrient levels. Here we describe the development of molecular strategies and their outcomes to meet minimum daily allowances for protein and iron in cassava based diets. We demonstrate that cyanogens play a central role in cassava nitrogen metabolism and that strategies employed to increase root protein levels result in reduced cyanogen levels in roots. We also demonstrate that enhancing root iron uptake has an impact on the expression of genes that regulate iron homeostasis in multiple tissues. These observations demonstrate the complex metabolic interactions involved in enhancing targeted nutrient levels in plants and identify potential new strategies for further enhancing nutrient levels in cassava.