Scope and Mechanistic Study of the Coupling Reaction of α,β-Unsaturated Carbonyl Compounds with Alkenes: Uncovering Electronic Effects on Alkene Insertion vs Oxidative Coupling Pathways

The cationic ruthenium-hydride complex [(C6H6)(PCy3)(CO)RuH]+BF4– (1) was found to be a highly effective catalyst for the intermolecular conjugate addition of simple alkenes to α,β-unsaturated carbonyl compounds to give (Z)-selective tetrasubstituted olefin products. The analogous coupling reaction of cinnamides with electron-deficient olefins led to the oxidative coupling of two olefinic C–H bonds in forming (E)-selective diene products. The intramolecular version of the coupling reaction efficiently produced indene and bicyclic fulvene derivatives. The empirical rate law for the coupling reaction of ethyl cinnamate with propene was determined as follows: rate = k[1]1[propene]0[cinnamate]−1. A negligible deuterium kinetic isotope effect (kH/kD = 1.1 ± 0.1) was measured from both (E)-C6H5CH═C(CH3)CONHCH3 and (E)-C6H5CD═C(CH3)CONHCH3 with styrene. In contrast, a significant normal isotope effect (kH/kD = 1.7 ± 0.1) was observed from the reaction of (E)-C6H5CH═C(CH3)CONHCH3 with styrene and styrene-d8. A pronounced carbon isotope effect was measured from the coupling reaction of (E)-C6H5CH═CHCO2Et with propene (13C(recovered)/13C(virgin) at Cβ = 1.019(6)), while a negligible carbon isotope effect (13C(recovered)/13C(virgin) at Cβ = 0.999(4)) was obtained from the reaction of (E)-C6H5CH═C(CH3)CONHCH3 with styrene. Hammett plots from the correlation of para-substituted p-X-C6H4CH═CHCO2Et (X = OCH3, CH3, H, F, Cl, CO2Me, CF3) with propene and from the treatment of (E)-C6H5CH═CHCO2Et with a series of para-substituted styrenes p-Y-C6H4CH═CH2 (Y = OCH3, CH3, H, F, Cl, CF3) gave the positive slopes for both cases (ρ = +1.1 ± 0.1 and +1.5 ± 0.1, respectively). Eyring analysis of the coupling reaction led to the thermodynamic parameters, ΔH⧧ = 20 ± 2 kcal mol–1 and ΔS⧧ = −42 ± 5 eu. Two separate mechanistic pathways for the coupling reaction have been proposed on the basis of these kinetic and spectroscopic studies

Étude expérimentale d'une paroi moulée ancrée par quatre nappes de tirants

Le Laboratoire Central des Ponts et Chaussées, l'entreprise SIF- BACHY et le Laboratoire de Mécanique des Solides de l'Ecole Polytechnique se sont associés pour l’étude expérimentale de la paroi moulée assurant la stabilité d'une fouille de 21 m de profondeur ouverte dans des formations typiques de la région parisienne, lors de la construction de l'immeuble de la S.E.R.E.T.E. à Paris dans le 13e arrondissement. Cette paroi moulée de 20,4 m de hauteur et de 0,60 m d’épaisseur était ancrée par 4 nappes de tirants précontraints. Au cours des travaux de terrassement on a mesuré la pression du sol sur la paroi, les déformations relatives du béton, les efforts dans les tirants et les déplacements de la paroi.Après une brève présentation de l'ouvrage et des caractéristiques géotechniques du site, les auteurs décrivent les dispositifs de mesure utilisés et rendent compte des résultats les plus caractéristiques obtenus lors des principales phases de travaux. Ces résultats sont ensuite analysés et discutés du point de vue de la fiabilité des mesures, d’une part et du point de vue du comportement de l'ouvrage, d'autre part. Dans la dernière partie de l'article, on compare les résultats expérimentaux aux résultats obtenus par le calcul aux éléments finis, dans l'hypothèse d'un comportement élastique du sol. et par le calcul élastoplastique au module de réaction

Supplementary Material for: Inclusion and Exclusion in Nutrigenetics Clinical Research: Ethical and Scientific Challenges

<i>Background/Aims:</i> There are compelling reasons to ensure the participation of ethnic minorities and populations of all ages worldwide in nutrigenetics clinical research. If findings in such research are valid for some individuals, groups, or communities, and not for others, then ethical questions of justice – and not only issues of methodology and external validity – arise. This paper aims to examine inclusion in nutrigenetics clinical research and its scientific and ethical challenges. <i>Methods:</i> In total, 173 publications were identified through a systematic review of clinical studies in nutrigenetics published between 1998 and 2007. Data such as participants’ demographics as well as eligibility criteria were extracted. <i>Results:</i> There is no consistency in the way participants’ origins (ancestry, ethnicity, or race) and ages are described in publications. A vast majority of the studies identified was conducted in North America and Europe and focused on ‘white’ participants. Our results show that pregnant women (and fetuses), minors, and the elderly (≧75 years old) remain underrepresented. <i>Conclusion:</i> Representativeness in nutrigenetics research is a challenging ethical and scientific issue. Yet, if nutrigenetics is to benefit whole populations and be used in public and global health agendas, fair representation as well as clear descriptions of participants in publications are crucial

Novel Olefin Metathesis Ruthenium Catalysts Bearing Backbone- Substituted Unsymmetrical NHC Ligands

none3noStable Ru-based catalysts containing unsym- metrical N-heterocyclic carbene (NHC) ligands with phenyl substituents on the backbone in syn and anti stereochemical relationships have been easily prepared and fully characterized. Preliminary investigation revealed that, depending on the backbone configuration, the new Ru complexes displayed different catalytic behaviors in representative olefin metathesis reactions.noneVeronica Paradiso; Valerio Bertolasi; Fabia GrisiVeronica, Paradiso; Bertolasi, Valerio; Fabia, Gris