Copper-Catalyzed Oxidation of Alkenes and Heterocycles

A variety of copper species catalyze the allylic oxidation of olefins and the introduction of an ester group at the α-position of a heterocycle. Both transformations are closely related in terms of reaction conditions and radical species involved. This short review highlights the progress made in these two types of oxidations, emphasizing work that has occurred within the last fifteen years

Multivariate optimization of the KharascheSosnovsky allylic oxidation of olefins

The multivariate optimization method known as simplex is applied to the KharascheSosnovsky allylic oxidation of double bonds. By applying this method, the amounts of three variables (copper source, oxidant, and additive) are optimized at the same time. Under the conditions thus obtained the reaction takes place in a considerable shorter time, being the alkene the limiting reagent. These conditions are applied to some monoterpenes and sesquiterpenes leading regioselectively to the corresponding benzoate esters, opening a route to the employment of this reaction in the synthesis of more complex molecules

Perception of Dating Violence in Teenage Couples: A Cross Validation Study in Spain and Colombia

Background: dating violence, or violence in teenage couples, is a socially interesting topic, due to its prevalence and its possible use in predicting violence in adult couples. The perception of violence, or the detection of abusive behaviors by teenagers and young people (which can be considered as equivalent concepts), is essential to prevent violence itself. Therefore, the main objective of this research is to determine which behaviors are identified as abusive by teenagers and young people, and the severity that they attribute to them¿meaning how they perceive them. Moreover, we will be able to determine whether there are differences between boys and girls in two countries: Spain and Colombia. Methods: for this study, we used two samples from both countries, with a total of 389 teenagers (50.9% females and 49.1% males) who were, on average, 16.56 years old (SD = 1.94 years). We analyzed the factorial invariance depending on sex and country of the sample and the different profiles of violence perception. Results: we found evidence of the internal validity of the questionnaire for what concerns the perception of inter-partner violence. The results point out that the perception of violence in the relationship is composed of two factors related to each other (Multiple and Emotional Abuse), which are invariant depending of sex and country of origin of the sample. The internal consistency of the test is adequate (>0.90). The analysis of the violence perception profiles indicates that Spanish teenagers have a higher perception of it, and, also, that girls hold a higher perception than boys. Conclusions: the results of this research have shown how dating violence (or violence in teenage couples) is differentially perceived not only between genders, but also across cultural contexts. Moreover, these outcomes may enhance the development of possible evidence-based interventions approaching the social problem generated by violence in teenage couples

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Optimization by Response Surface Methodology (RSM) of the Kharasch−Sosnovsky Oxidation of Valencene

Response surface methodology (RSM) has been employed to model and optimize the Kharasch−Sosnovsky allylic oxidation of valencene. The detailed effects of the amounts of oxidant, substrate, copper catalyst, 1,8- diazabicyclo[5.4.0]undec-7-ene (DBU), and temperature have been studied. The concentration of substrate and quantity of oxidant have been determined as the most significant variables. The interaction effects on the yield have been investigated using a three-level full-factorial design. The yield of benzoyloxyvalencene has been improved to 99%. Analysis of variance (ANOVA) has been used to evaluate the goodness of fit of the model

Insights into pneumococcal fratricide from the crystal structures of the modular killing factor LytC

7 pags, 3 figs, 1 tabThe first structure of a pneumococcal autolysin, that of the LytC lysozyme, has been solved in ternary complex with choline and a pneumococcal peptidoglycan (PG) fragment. The active site of the hydrolase module is not fully exposed but is oriented toward the choline-binding module, which accounts for its unique in vivo features in PG hydrolysis, its activation and its regulatory mechanisms. Because of the unusual hook-shaped conformation of the multimodular protein, it is only able to hydrolyze non-cross-linked PG chains, an assertion validated by additional experiments. These results explain the activation of LytC by choline-binding protein D (CbpD) in fratricide, a competence-programmed mechanism of predation of noncompetent sister cells. The results provide the first structural insights to our knowledge into the critical and central function that LytC plays in pneumococcal virulence and explain a long-standing puzzle of how murein hydrolases can be controlled to avoid self-lysis during bacterial growth and division. © 2010 Nature America, Inc. All rights reserved.This work was supported by grants from the Spanish Ministry of Science and Technology (BFU2008-01711, SAF2006-00390), EU-CP223111 (CAREPNEUMO, European Union), the COMBACT program (S-BIO-0260/2006) and CIBER de Enfermedades Respiratorias (CIBERES). CIBERES is an initiative of Instituto de Salud Carlos III. The work in the US was supported by the US National Institutes of Health. W.V. was supported by the European Commission (EUR-INTAFAR project). I.P.-D. was a fellow of the Consejo Superior de Investigaciones Científicas

Influence of the carbon support on the PtSn anodic catalyst for the electrochemical reforming of ethanol

Several anodic catalysts based on Pt–Sn (3:1 mass ratio) and 20% total metal loading were prepared on different carbonaceous supports (functionalized and non-functionalized low-density nanofibers, graphite oxide, expanded graphite, graphene flakes and β-SiC), to identify an alternative for the traditional Carbon Vulcan XC-72 support for the electrochemical reforming of ethanol. Of the materials tested, Pt–Sn supported on non-functionalized low-density nanofibers (CNF LS) showed the highest electro-catalytic activity vs. the traditional support. This result was attributed to the combination of different properties such as high surface area and dispersion of the Pt–Sn nanoparticles, high electrochemical active surface area and high basicity. This anodic catalyst was chosen for the development of a Membrane Electrode Assembly (MEA) and tested for the electrochemical reforming of ethanol. A high activity was obtained (120 mA cm−2 at 1.4 V and 80 °C) for hydrogen production. In addition, the stability of the system and its subsequent regeneration were studied in view of its practical application.Se prepararon varios catalizadores anódicos basados en Pt-Sn (relación de masas 3:1) y con una carga total del 20% de metal sobre diferentes soportes carbonosos (nanofibras de baja densidad funcionalizadas y no funcionalizadas, óxido de grafito, grafito expandido, escamas de grafeno y β-SiC), para identificar una alternativa al soporte tradicional Carbon Vulcan XC-72 para el reformado electroquímico del etanol. De los materiales ensayados, el Pt-Sn soportado sobre nanofibras de baja densidad no funcionalizadas (CNF LS) mostró la mayor actividad electrocatalítica frente al soporte tradicional. Este resultado se atribuyó a la combinación de diferentes propiedades, como la elevada superficie y dispersión de las nanopartículas de Pt-Sn, la elevada superficie electroquímicamente activa y la alta basicidad. Este catalizador anódico se eligió para el desarrollo de un conjunto de electrodos de membrana (MEA) y se probó para el reformado electroquímico del etanol. Se obtuvo una elevada actividad (120 mA cm-2 a 1,4 V y 80 °C) para la producción de hidrógeno. Además, se estudió la estabilidad del sistema y su posterior regeneración con vistas a su aplicación práctica

Acyloxylation of 1,4-Dioxanes and 1,4-Dithianes Catalyzed by a Copper−Iron Mixed Oxide

The use of a copper−iron mixed oxide as a heterogeneous catalyst for the efficient synthesis of α-acyloxy-1,4-dioxanes and 1,4-dithianes employing t-butyl peroxyesters is reported. The preparation and characterization of the catalyst are described. The effect of the heteroatoms and a plausible mechanism are discussed. The method is operationally simple and involves low-cost starting materials affording products in good to excellent yields

DoE (Design of Experiments) Assisted Allylic Hydroxylation of Enones Catalysed by a Copper–Aluminium Mixed Oxide

The allylic hydroxylation of enones using dioxygen as the oxidant has been studied. The reaction was first examined in the absence of any catalyst, using β-ionone as a model substrate. Then a new copper–aluminium mixed oxide, Cu–Al Ox, was prepared and characterized in order to be used as a catalyst. This oxide showed good activity, and provided the corresponding γ- or ε-hydroxylated enones, starting from different α,β- or α,β,γ,δ-unsaturated ketones. In all cases, the yields were significantly improved compared to experiments run in the absence of the catalyst. The reaction was selective, and the formation of epoxides or other overoxidation products was detected only to a minor extent. The described procedure is a technically straightforward synthetic alternative to those methods described to date involving many reaction steps or toxic reagents. The reactions were optimized using design of experiments techniques (DoE)