Regiodivergent Cyclobutanone Cleavage: Switching Selectivity with Different Lewis Acids

The exploitation of strain release in small rings as driving force to enable complex transformations is a powerful synthetic tool. Among them, cyclobutanones are particularly versatile substrates that can be elaborated in a wide variety of structurally diverse building blocks. Herein, Lewis acid catalyzed rearrangement reactions are presented that provide selective access to two structurally distinct polycyclic scaffolds, that is, indenylacetic acid derivatives and benzoxabicyclo[3.2.1]octan‐3‐ones. The choice of the Lewis acid fully controls the reaction pathway and the regioselectivity of the cyclobutanone C?C bond cleavage site.     

A Tris(triazolate) Ligand for a Highly Active and Magnetically Recoverable Palladium Catalyst of Selective Alcohol Oxidation Using Air at Atmospheric Pressure

High efficiency and selectivity, easy magnetic recovery and recycling, and use of air as the oxidant at atmospheric pressure are major objectives for oxidation catalysis in terms of sustainable and green processes. A tris(triazolyl) ligand, so far only used in copper‐catalyzed alkyne azide cycloadditions, was found to be extremely efficient in SiO₂/γ‐Fe₂O₃‐immobilized palladium complexes. It was characterized by inductively coupled plasma (ICP) analysis, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy‐dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectra (XPS) and found to fulfill the combined conditions for the selective oxidation of alcohols to aldehydes and ketones.     

Detection of oligonucleotide gas-phase conformers: H/D exchange and ion mobility as complementary techniques

Gas-phase hydrogen/deuterium exchange of small oligonucleotides (dTG, dC(6) and C(6)) with CD(3)OD was performed in the second hexapole of a Fourier transform ion-cyclotron resonance (FTICR) mass spectrometer. Ion activation experiments were conducted by accelerating the ions at the entrance of the H/D exchange cell under conditions promoting exclusively collisional isomerization. These experiments allowed us to assess the presence of several conformers, and to probe the height of the isomerization barrier separating these conformers. Ion mobility experiments were also performed. Their results were consistent with the H/D exchange data. A model accounting for the competing isomerization and H/D exchange reactions is proposed. Comparing the ion acceleration experiments for H/D exchange and for ion mobility reveals that the most compact conformer displays the fastest H/D exchange. This observation shows that H/D exchange and ion mobility provide us with complementary information because hydrogen accessibility and macromolecule compactness are not univocally associated.     

Synthesis and supramolecular organization of amphiphilic diblock copolymers combining poly(N,N-dimethylamino-2-ethyl methacrylate) and poly(epsilon-caprolactone)

Well-defined poly(epsilon-caprolactone) (PCL)/poly(N,N-dimethylamino-2-ethyl methacrylate (PDMAEMA) diblock copolymers were synthesized, and their self-assembly was investigated as micelles both in aqueous solutions and in thin solid deposits. The synthetic approach combines controlled ring opening polymerization (ROP) of epsilon-caprolactone (CL) and atom transfer radical polymerization (ATRP) of N,N-dimethylamino-2-ethyl methacrylate (DMAEMA). Diblock copolymers were prepared by ROP of CL initiated by (Al(OiPr)3), followed by quantitative reaction of the PCL hydroxy end-groups with bromoisobutyryl bromide. The alpha-isopropyloxy omega-2-bromoisobutyrate poly(epsilon-caprolactone) (PCL-Br) obtained was used as a macroinitiator for the ATRP of DMAEMA. The molecular characterization of those diblock copolymers was performed by 1H NMR spectroscopy and gel permeation chromatography (GPC) analysis. The self-assembly of the copolymers into micellar aggregates in aqueous media was followed with dynamic light scattering (DLS), as a function of concentration and the pH. In parallel, the morphology of the solid deposits of those micelles was examined with atomic force microscopy (AFM).     

Synergies between operations research and data mining: The emerging use of multi-objective approaches

Operations research and data mining already have a long-established common history. Indeed, with the growing size of databases and the amount of data available, data mining has become crucial in modern science and industry. Data mining problems raise interesting challenges for several research domains, and in particular for operations research, as very large search spaces of solutions need to be explored. Hence, many operations research methods have been proposed to deal with such challenging problems. But the relationships between these two domains are not limited to these natural applications of operations research approaches. The counterpart is also important to consider, since data mining approaches have also been applied to improve operations research techniques. The aim of this article is to highlight the interplay between these two research disciplines. A particular emphasis will be placed on the emerging theme of applying multi-objective approaches in this context.     

The pattern of methylcyclopentane and n-hexane reactions on Rh/Al2O3 in catalytic runs of various length

Methylcyclopentane and n-hexane were reacted on a Rh/alumina catalyst in a closed-loop reactor. The product composition was analyzed at different moments of the run. In spite of a slow self-deactivation, the distribution of primary products and the depth of hydrogenolysis showed hardly any dependence on the sampling time in the conversion range of 1.5% and 50%. This is discussed in terms of accumulation of hydrocarbonaceous residues and the low readsorption probability of primary products on rhodium surface.     

A strategy for isotope containment during radiosynthesis--devolatilisation of bromobenzene by fluorous-tagging-Ir-catalysed borylation en route to the 4-phenylpiperidine pharmacophore

Syntheses of two 4-phenylpiperidines from bromobenzene have been developed involving anchoring to a fluorous-tag, Ir-catalysed borylation, Pd- and Co-catalysed elaboration then traceless cleavage. Although performed using 'cold' (i.e. unlabelled) bromobenzene as the starting material, these routes have been designed to minimise material loss via volatile intermediates and expedite purification during radiosynthesis from 'hot' (i.e. [(14)C] labelled) bromobenzene.     

Synthesis and spectroscopic examination of various substituted 1,3-dibenzoylmethane, active agents for UVA/UVB photoprotection

We describe the synthesis of eighteen variously substituted 1,3- dibenzoylmethane (1,3-DBM) and their change in absorption spectra depending of the nature of donor or acceptor substituents on one or the two aromatic moieties. These compounds were prepared in two steps starting from the corresponding acetophenones, phenol and benzoyl chlorides. The phenyl benzoate was obtained by condensation of benzoyl chloride with phenol in a classical way. Stirring of the phenyl benzoate and acetophenone in DMSO with powdered sodium hydroxide for a few minutes gave the dibenzoylmethane in yields depending on substituents on the phenyl rings. Changes in absorption of UVA/UVB sunlight of these molecules were observed according to the nature and the position of substituents on the phenyl rings. Molecules 2b (1-phenyl-3-(3,4,5-trimethoxyphenyl)-1,3-propanedione), 2d (1-(3,4-dimethoxyphenyl)-3-phenyl-l,3-propanedione), 2e (1-(2,3-dimethoxyphenyl)-3-phenyl-l,3-propanedione) and 2f (1-(2,3,4-trimethoxyphenyl)-3-phenyl-l,3-propanedione) were the most interesting for cosmetic applications because even after irradiation, they preserve their absorptive in UVA range and also in UVB range The other compounds are too photounstable and so can lose their protective effects. These results showed the lack of phototoxicity of these compounds and the possibility to use them as solar filters. Therefore, variously di- or tri methoxy 1,3-DBM are interesting molecules in term of photoprotection and open new prospects for UVA photostable filters.     

High order variational numerical schemes with application to Nash–MFG vaccination games

This paper introduces high-order explicit Runge–Kutta numerical schemes in metric spaces. We show that our approach reduces to the corresponding Runge–Kutta schemes if the ambient space is Hilbert. We apply these schemes to compute the Nash equilibrium in a mean field vaccination game. Numerical simulations show improvement in the speed of convergence towards the Nash equilibrium; the numerical scheme has high order (2–4) in time.