Oxidation by DMSO I. Opening Of Epoxides into α-Hydroxyketones in Presence of KSF Clay Under Microwave Irradiation

α-Hydroxyketones were readily obtained from epoxide by reaction with DMSO in presence of KSF clay under microwave irradiation.     

Phosphonated Polyethylenimine‐Coated Nanoparticles: Size‐ and Zeta‐Potential‐Adjustable Nanomaterials

Novel partially phosphonated polyethylenimine polymers are developed in order to control the modification of nanoparticle (NP) surfaces. This polymer is built by an accessible one‐step process. The numerous phosphonate functions assume both a strong covalent anchoring on metal oxide NPs and a modulation of electric charges, while amino groups are associated with dispersion preservation and subsequent biofunctionalization. The zwitterionic nanomaterials obtained display a good stability toward pH and ionic strength. According to the selected percentage of phosphonation and the polymer size, zeta potential, and diameter of the particles are controlled.     

New highlights on degradation process of verdigris from easel paintings

Verdigris is a green copper organometallic pigment, widely used in paintings during the fifteenth and sixteenth centuries. With ageing, chromatic modifications like browning or darkening can be observed on those green painted layers. An original but crucial approach has been developed based on the characterization of a reference neutral verdigris pigment—anhydrous copper acetate—and model samples, made of verdigris and linseed oil. Samples have undergone artificial ageing (temperature, light) to reproduce the color change effect. They were analysed before and after accelerated ageing tests by a complementary set of classical techniques: colorimetry, electron paramagnetic resonance, X-ray absorption spectroscopy, and UV–visible absorption. Our experiments revealed that the incorporation of the verdigris pigment in linseed oil induces a transformation of the copper acetate bimetallic structure, with the formation of monomeric species. These monomers, however, are not directly responsible for the darkening. The chromatic alteration seems instead linked to the transient formation of Cu(I) in the copper complexes of the pigment/oil system. This formation could be initiated by ambient light absorption through ligand-to-metal charge transfer, which favors the decarboxylation of the copper complexes leading to the reduction of Cu(II) into Cu(I). Moreover, dioxygen can react with partially decarboxylated dimers to form peroxy-Cu dimer complexes that can be responsible for the darkening.     

A new multicomponent reaction for the synthesis of pyridines via cycloaddition of azadienes and ketenimines

The ketenimines resulting from a Nef isocyanide/Perkow sequence react with 1-azadienes to form pyridines or pyrimidines depending on their substitution pattern. The reaction is most efficient with ester-substituted ketenimines which leads to pyridines after elimination of the phosphate group.     

First highly stereocontrolled synthesis of the unusual 1-hydroxy endo,endo-2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane lignan skeleton

This Letter describes a highly diastereoselective synthesis of the unique 1-hydroxy endo,endo-2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane skeleton starting from a stereodefined 4-arylidenetetrahydrofuran obtained by a multicomponent reaction. The key step of this synthesis is a dealkylative cyclization reaction performed on the corresponding epoxide, generating four contiguous stereogenic centers with total stereocontrol.     

Thermo sensitive behavior of cellulose derivatives in dilute aqueous solutions: from macroscopic to mesoscopic scale

Thermal behaviors of thermo sensitive hydroxypropyl cellulose (HPC), methyl cellulose (MC) and methyl hydroxypropyl cellulose (MHPC) solutions have been investigated in dilute regime of concentration (C相似文献   

A crystalline σ complex of copper

Over the last decades, our understanding of σ-bond activation at transition metals has progressed considerably from both fundamental and synthetic points of view thanks to the preparation and characterization of a variety of σ complexes. Here we report the synthesis and structural analysis of the first σ complex involving a coinage metal. The copper(I) complex 2 derived from the diphosphine-disilane [Ph(2)P(C(6)H(4))Me(2)Si-SiMe(2)(C(6)H(4))PPh(2)] (1) has been isolated and crystallographically characterized. The coordination of the Si-Si σ bond to copper was thoroughly analyzed by quantum-chemical methods.     

Hydrotrope-induced inversion of salt effects on the cloud point of an extended surfactant

We report on the effects of electrolytes spanning a range of anions (NaOc, NaSCN, NaNO(3), NaBr, NaCl, NaBu, NaOAc, Na(2)SO(4), Na(2)HPO(4), and Na(2)CO(3)) and cations (LiCl, NaCl, KCl, CsCl, and choline chloride) on the aqueous solubility of an extended surfactant. The surfactant is anionic with a long hydrophobic tail as well as a significant fraction of propylene oxide groups and ethylene oxide groups (C(12-14)-PO(16)-EO(2)-SO(4)Na, X-AES). In the absence of electrolytes, X-AES exhibits a cloud-point temperature that decreases with increasing surfactant concentration. After the addition of salts to the surfactant solutions, various shifts in the solubility curves are observed. These shifts follow precisely the same Hofmeister series that is found for salting-in and salting-out effects in protein solutions. In the presence of different concentrations of sodium xylene sulfonate (SXS), the solubility of the surfactant increases. In this context, SXS can be considered to be a salting-in salt. However, when the electrolytes are added to an aqueous solution of X-AES and SXS the Hofmeister series reverses for divalent anions such as Na(2)SO(4), Na(2)HPO(4), and Na(2)CO(3). Studies on the phase behavior and micelle structures using polarization microscopy, freeze-etch TEM, and NMR measurements indicate a dramatic change in the coexisting phases on the addition of SXS.