Disproportionation reaction of diarylcarbinols: a versatile access to diarylmethanes speeded up using microwave irradiation

International audienceAn efficient synthesis of diarylmethanes under classical thermal conditions and under microwave heating has been established from diarylcarbinols via a new disproportionation reaction. The key step involve a selective hydride transfert of iso-propylic ethers intermediates. Soft experimental procedure using catalytic CBr4 or TfOH in i-PrOH and good yields render this method useful and competitive to the conventional approaches relying on application of external reducing agents

Conception et synthèse de dendrimères poly(arylpropargyléther) (pape) comme vecteurs potentiels de principes actifs

La vectorisation d'un principe actif permet de maîtriser son transport et sa distribution jusqu'à sa cible cellulaire dans le but notamment d'améliorer les traitements et de diminuer les effets indésirables. Les dendrimères sont des macromolécules isomoléculaires, obtenues par la réaction d'un cœur plurifonctionnalisé avec des dendrons (Voie convergente). Leurs caractéristiques principales (forme globulaire, cavités, fonctions terminales à la surface,) leur offrent des perspectives intéressantes dans le cadre de la vectorisation. Nous avons proposé la synthèse convergente de dendrimères PAPE (poly(arylpropargyléther)), dont le motif itératif arylpropargyléther composant les dendrons est introduit par une séquence réactionnelle de trois étapes (addition-1,2, réaction de Williamson, et couplage de Sonogashira). Dans un premier temps, nous avons synthétisé des dendrons de première et seconde génération iodés, à partir desquels sont introduits, par une réaction de Sonogashira, des alcools de longueur de chaîne différente. Les dendrons ainsi obtenus ont conduit aux dendrimères de liaison cœur-dendron de type ester, par une réaction de Mitsunobu avec le cœur, l'acide 1,3,5-benzènetricarboxylique. D'autre part, les dendrons de première et seconde génération substitués par une fonction phénol ont été synthétisés. Ils nous ont permis d'obtenir les dendrimères de liaison cœur-dendron de type ester (à partir du 1,3,5-trichlorure de benzoyle) ou de type éther (à partir du 1,3,5-trisbromométhylbenzène) (dendrimères "linéaires"). De plus, des dendrimères dont le nombre de branches croît en fonction de la génération ont été synthétisés, ces dendrimères dits "dédoublés" de première génération se caractérisent par une masse moléculaire équivalente aux dendrimères dits "linéaires" de seconde génération. Dans le but d'améliorer la solubilité dans l'eau de ces dendrimères, des fonctions esters d'alkyles fonctionnalisés par des groupements aminés (susceptibles de former des sels d'ammonium) ont été introduites par une réaction de trans-estérification. Les tests biologiques de ces dendrimères restent à réaliser enfin de déterminer leur cytotoxicitéDrug-delivery system are attractive as a means of effectively controlling drug transport and for targeting specific cells. These systems aim to enhance treatment efficacy and to avoid side effects. Dendrimers are mono-dispersed macromolecules (of a single molecular weight), prepared by coupling a core to several branches (or dendrons) in the convergent growth approach. They also have numerous surface fonctionnalities as well as internal cavities. These features make them attractive for drug-delivery applications. We explored a convergent strategy to new poly(arylpropargylether) (PAPE) dendrimers. The arylpropargylether unit is introduced by a three-step sequence : addition of a Grignard reagent to an aldehyde, Williamson reaction with propargyl bromide and Sonogashira cross-coupling with functionalised aromatic halides. The anchorings of the dendrons to cores are of two kinds: benzylic ether and ester. Different polyamino or polyol groups have been introduced at the surface of the dendrimer in the aim of improve their water solubility. Further investigations of these dendrimers toward their biocompatibility and cell cytotoxicity are in progressCHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Molten salt setup analysis

International audienceThe CEA is developing safer and more modular next-generation reactors. Among the diversity of new reactors considered, there is a family that would use molten salts as coolant (MSR). This solution offers many advantages but requires solving some problems related to the corrosion of metals by salts.The corrosion study can be quite long and would be considerably accelerated if an in-situ measurement of the chemical composition of the salts was available. Because LIBS technic is an all optical sensor, it would make it possible to achieve this. However, the constraints related to temperature, inertness of the salts, narrowness of access make accessibility non-trivial. The work will present the optical study that has been done as well as the stability study of the signal obtained with the selected setup on a simulating liquid medium

Advances in the laser pyrolysis synthesis of nanoparticles

National audienc

A 50-year analysis of hydrological trends and processes in a Mediterranean catchment

International audienceThe Réal Collobrier hydrological observatory in southeastern France, managed by Irstea since 1966, constitutes a benchmark site for regional hydro-climatology. Because of the dense network of stream gauges and rain gauges available, this site provides a unique opportunity to evaluate long-term hydro-meteorological Mediterranean trends. The main catchment (70 km²) and its sub-catchments are located in the massif des Maures of southeastern France, close to the Mediterranean coast. The vegetation is composed of forest mainly calcified on crystalline soils (maquis of heath, cork-oak, maritime pine and chestnut). Direct human influence has been negligible over the past 50 years. The land use and land cover has remained almost unchanged, with the notable exception of a wildfire in 1990 that impacted a small sub-catchment. Therefore changes in the hydrological response of the catchments are caused by changes in climate and/or physical conditions. This study investigates changes in observational data using up to 50-year daily series of precipitation and streamflow. The analysis used several climate indices describing distinct modes of variability, at inter-annual and seasonal timescales. Trends were assessed by the Mann-Kendall method. The analysis also used hydrological indices describing drought events based on daily data for a description of low flows, in particular in terms of timing and severity. The analysis shows that there is a marked tendency towards a decrease in the water resources of the Réal Collobrier catchment in response to climate trends, with a consistent increase in drought severity and duration. But the changes are variable among the sub-catchments

A 50-year analysis of hydrological trends and processes in a Mediterranean catchment

International audienceThe Réal Collobrier hydrological observatory in southeastern France, managed by Irstea since 1966, constitutes a benchmark site for regional hydro-climatology. Because of the dense network of stream gauges and rain gauges available, this site provides a unique opportunity to evaluate long-term hydro-meteorological Mediterranean trends. The main catchment (70 km²) and its sub-catchments are located in the massif des Maures of southeastern France, close to the Mediterranean coast. The vegetation is composed of forest mainly calcified on crystalline soils (maquis of heath, cork-oak, maritime pine and chestnut). Direct human influence has been negligible over the past 50 years. The land use and land cover has remained almost unchanged, with the notable exception of a wildfire in 1990 that impacted a small sub-catchment. Therefore changes in the hydrological response of the catchments are caused by changes in climate and/or physical conditions. This study investigates changes in observational data using up to 50-year daily series of precipitation and streamflow. The analysis used several climate indices describing distinct modes of variability, at inter-annual and seasonal timescales. Trends were assessed by the Mann-Kendall method. The analysis also used hydrological indices describing drought events based on daily data for a description of low flows, in particular in terms of timing and severity. The analysis shows that there is a marked tendency towards a decrease in the water resources of the Réal Collobrier catchment in response to climate trends, with a consistent increase in drought severity and duration. But the changes are variable among the sub-catchments

Identification et hierarchisation des pesticides les plus préoccupants sur le plan de la santé et de l'environnement

Afin de lister et d'ordonner les produits phytosanitaires utilisés en agriculture les plus préoccupants pour l'Homme et pour l'Environnement, nous mettons en oeuvre une approche originale de type "hiérarchisation multicritère". Cette démarche permet de rendre compte du comportement des pesticides dans les différents compartiments de l'environnement sans pour autant recourir à une description fine d'une grande finesse des processus physiques, biologiques et chimiques à l'oeuvre. Dans sa version la plus simple, ce système de hiérarchisation s'accommode donc d'un certain degré d'incertitude et d'un nombre très restreint de données d'entrée : ceci se traduit par une grande simplicité d'utilisation particulièrement appréciée dans la gestion des problématiques environnementales. La mise en oeuvre de cette démarche sur un territoire donné aboutit au classement des substances actives phytosanitaires employées localement: la liste obtenue est organisée suivant la susceptibilité décroissante des substances à impacter l'environnement (eaux, air, sol) ou la santé humaine

Identification and classification of pesticides for health and environment : Sph'Air, a decision support system for air monitoring

International audienceSph'air is a decision support system aiming to classify pesticides according to the level of concern caused by their presence in the atmosphere. The classification is carried out via a multicriteria analysis method. The criteria used are quantities of pesticides sold in France, their air persistence, atmospheric sources and toxicity. The classification results were compared to pesticides monitored in air. Sph'air correctly identified the most often detected substances in the atmosphere. The French National Institute for Industrial Environment and Risks (INERIS) has developed this decision support system with the French National Institute for Agricultural Research (INRA) and the Public Research Institute studying land and water management (CEMAGREF). Financed by the French "Région Picardie" and French Environment and Agriculture Ministries, this project is supervised by a steering committee composed of policy makers, scientists, industrialists and associations