Ruthenium-catalyzed synthesis of allylic alcohols: boronic acid as a hydroxide source

Secondary allylic alcohols were synthesized from linear allylic halides or carbonates using a catalytic amount of a ruthenium complex in the presence of boronic acid. The effects of solvent, base, ruthenium precursor, and boronic acid were fully explored, and the scope of the reaction was extended to various substrates. We also describe a preliminary investigation towards an enantioselective process.     

An efficient and facile synthesis of highly substituted 2,6-dicyanoanilines

A one-pot procedure for the synthesis of substituted 2,6-dicyanoanilines starting from readily available ynones and malononitrile has been developed. For instance, penta-1,4-diyn-3-one is converted into the acetylene-substituted aniline derivative 1 in good yield. Upon photoexcitation, this chromophore shows a strong blue emission with a high quantum yield. The ground- and the excited-state geometries, charge distributions, and excitation energies of 1 have been evaluated by ab initio calculations.     

Oligothiophene-functionalized CdSe nanocrystals: preparation and electrochemical properties

The preparation of new molecular hybrids consisting of CdSe semiconductor nanocrystals, surface-functionalized with conductive and electrochemically active oligothiophene ligands, is described. Specially synthesized aniline-terminated oligoalkylthiophenes containing one, two, or four thiophene units were used for the grafting on CdSe nanocrystals, previously surface-functionalized with 4-formyldithiobenzoate. The electrochemical activity of both the inorganic and the organic parts of the hybrid was investigated by cyclic voltammetry. The oxidative doping of the organic part of the hybrid is irreversible, contrary to the case of the “free” non-grafted ligand which shows reversible doping. Furthermore, the electrochemical doping of the surface ligands, occurring at lower potentials than the oxidation of the nanocrystals, perturbs the latter process via charging of the ligands followed by slow relaxation processes. The first two authors contributed equally to this work Correspondence: Peter Reiss, Adam Pron, DSM/DRFMC/SPrAM (UMR 5819 CEA-CNRS-Université Joseph Fourier 1)/LEMOH CEA Grenoble, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France     

Pentamethylcyclopentadienyl ruthenium: an efficient catalyst for the redox isomerization of functionalized allylic alcohols into carbonyl compounds

The catalytic activity of the ruthenium(II) complex [RuCp^∗(CH₃CN)₃][PF₆] 1 in the transposition of allylic alcohols into carbonyl compounds, in acetonitrile, is reported. This catalyst has proven to be able to catalyze the transformation of poorly reactive and/or functionalized substrates under smooth conditions.     

Continuous separation of cells by balanced dielectrophoretic forces at multiple frequencies

We present a particle-sorting device based on the opposition of dielectrophoretic forces. The forces are generated by an array of electrode chambers located in both sidewalls of a main flow channel. Particles with different dielectric response perceive different force magnitudes and are therefore continuously focused to different streamlines in the flow channel. We relate the particles' dielectric response to their output position in the downstream channel. We demonstrate the performance of the device by separating a mixed yeast cell population into pure fractions of viable and nonviable cells. Finally, we use the device to enrich red blood cells infected with Babesia bovis, a major pathogen in cattle and simultaneously confirm the hypothesis that infection with B. bovis causes significant changes in the dielectric response of red blood cells.     

Approximate solution of a resource-constrained scheduling problem

This paper is devoted to the approximate solution of a strongly NP-hard resource-constrained scheduling problem which arises in relation to the operability of certain high availability real time distributed systems. We present an algorithm based on the simulated annealing metaheuristic and, building on previous research on exact solution methods, extensive computational results demonstrating its practical ability to produce acceptable solutions, in a precisely defined sense. Additionally, our experiments are in remarkable agreement with certain theoretical properties of our simulated annealing scheme. The paper concludes with a short discussion on further research. This research was supported in part by Association Nationale de la Recherche Technique grant CIFRE-121/2004.     

A radical procedure for the anti-Markovnikov hydroazidation of alkenes

A one-pot procedure for the efficient hydroazidation of alkenes involving hydroboration with catecholborane followed by reaction with benzenesulfonyl azide in the presence of a radical initiator is described. The regioselectivity is controlled by the hydroboration step and corresponds in most cases to an anti-Markovnikov regioselectivity. This procedure is applicable to a wide range of alkenes and gives excellent results with 1,2-disubstituted and trisubstituted alkenes.     

p-Xylene-selective metal-organic frameworks: a case of topology-directed selectivity

Para-disubstituted alkylaromatics such as p-xylene are preferentially adsorbed from an isomer mixture on three isostructural metal-organic frameworks: MIL-125(Ti) ([Ti(8)O(8)(OH)(4)(BDC)(6)]), MIL-125(Ti)-NH(2) ([Ti(8)O(8)(OH)(4)(BDC-NH(2))(6)]), and CAU-1(Al)-NH(2) ([Al(8)(OH)(4)(OCH(3))(8)(BDC-NH(2))(6)]) (BDC = 1,4-benzenedicarboxylate). Their unique structure contains octahedral cages, which can separate molecules on the basis of differences in packing and interaction with the pore walls, as well as smaller tetrahedral cages, which are capable of separating molecules by molecular sieving. These experimental data are in line with predictions by molecular simulations. Additional adsorption and microcalorimetric experiments provide insight in the complementary role of the two cage types in providing the para selectivity.     

Silylboranes as new sources of silyl radicals for chain-transfer reactions

Various silylboranes, which were outfitted with a catecholborane moiety at one end and a (Me(3)Si)(3)Si moiety at the other end of a carbon chain, were prepared through the hydroboration of the corresponding unsaturated silanes. The C-centered radical species generated from these silylboranes efficiently cyclized to provide, through a 5-exo intramolecular homolytic substitution at the silicon center, the corresponding silacycle and a Me(3)Si radical that was subsequently trapped by sulfonyl acceptors. These cyclizations proceeded at unprecedented rates, due, in part, to a strong gem-dialkyl effect that was attributable to the presence of bulky substituents on a quaternary center located on the chain. In parallel, we designed arylsilylboranes that produced silyl radicals through a 1,5-hydrogen transfer. Such silyl radicals may be valuable radical chain carriers, for instance, in oximation reactions of alkyl halides. Finally, computational studies allowed calculation of activation barriers of the homolytic substitution step and additionally illustrated that the overall reaction mechanism involved a transition state in which the attacking carbon center, the central silicon atom, and the Me(3)Si leaving group were collinear.