Fe3O4 nanoparticles/ethyl acetoacetate system for the efficient catalytic oxidation of aldehydes to carboxylic acids

A new methodology for the oxidation of aldehydes promoted by commercially available Fe₃O₄ nanoparticles (Fe₃O₄ NPs) activated by ethyl acetoacetate was developed. The use of ethyl acetoacetate as additive was crucial to achieve high reactivities. All reactions were realized under solvent free conditions, using air or tBuOOH as oxidants. Finally, the separation and reuse of the magnetically recoverable nanoparticles make this methodology very practical, simple and economical.     

4,5-Dihydro-7,8-dimethoxy-1-phenyl-3H-2,3-benzodiazepin-4-one

The title compound, C₁₇H₁₆N₂O₃, is an antagonist for AMPA/kainate receptors. The mol­ecule has its seven-membered oxa­diazo­le ring in a boat conformation. Asymmetry of the two methoxy bond angles is evident, with (Me)O—C—C angles of 115.45 (12) and 124.78 (13)°, and 114.67 (12) and 125.31 (12)°. A centrosymmetric dimer involving the HN—CO moieties, with an N⃛O distance of 2.876 (2) Å, graph set R(8), is further linked into chains through methoxy Csp³—H⃛N hydrogen bonds, with a C⃛N distance of 3.418 (2) Å.     

Venttsel’ problems in fractal domains

A nonsteady Venttsel’ problem in a fractal domain Ω or in the corresponding prefractal domain Ω _h is studied. Existence, uniqueness, and regularity results for the strict solution, in both cases, are established as well as convergence results of the solutions of the approximating problems in varying Hilbert spaces.     

Role of polymer network and gelation kinetics on the mechanical properties and adsorption capacity of chitosan hydrogels for dye removal

Chitosan (CS) hydrogels are receiving growing attention as adsorbents for water purification purposes. The conditions of preparation of this class of materials play a crucial in the determination of their performances; however, this aspect is often neglected in the literature. In this study, we deal with this issue, focusing on the structure‐property relationships of CS hydrogels obtained by phase inversion method. We show that the concentration of the starting solution determines the density and strength of intermolecular interactions, and that the gelation kinetics dictates the hydrogel structure at the microscale. Consequently, even subtle changes in the preparation protocol can cause significant differences in the performances of CS hydrogels in terms of mechanical properties and dye adsorption capacity. The observed trends are often neither trivial nor monotonic. Nonetheless, we demonstrate that they can be interpreted looking at the CS network structure, which can be inferred by rheological measurements. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1843–1849     

Homogenization for conductive thin layers of pre-fractal type

The aim of this work is to obtain convergence results for the solutions of transmission problems across highly conductive layers of pre-fractal type from the point of view of homogenization. We prove the M-convergence of the energy functionals to an energy functional which incorporates a singular term, supported within the layer. From the convergence of the energy functionals we deduce the convergence of the approximating solutions to the limit solution in a suitable sense.     

New chiral imino- and amino-sulfoxides as activators of allyl trichlorosilane in the asymmetric allylation of aldehydes

Chiral 2-methylsulfinyl benzaldehyde proved to be a valuable starting material for a convenient approach towards a variety of imino- and amino-sulfoxides. The catalytic properties of these new ligands, as potential activators of allyl trichlorosilane, have been exploited in new catalytic procedures for the synthesis of enantioenriched homoallylic alcohols.     

Spiroketals of monosaccharides by dye-sensitized photooxygenation of furyl ketoses

[4+2] Cycloaddition of singlet oxygen to suitably substituted furans followed by reduction of the corresponding endoperoxides afforded functionalized enediones which quickly cyclized into the titled spiroketals. The reported method represents a green synthetic one-pot procedure for novel [6,6]-, [5,6]-, and [5,5]-spiroketals of sugars.     

Dye-sensitized photooxygenation of sugar furans: novel bis-epoxide and spirocyclic C-nucleosides

Dye-sensitized photooxygenation of 2-methyl 5-(2,3,5-tri-O-acetyl-β-d-ribofuranosyl)furoate leads to (1S,4R)-endo-peroxide, highlighting a high facial diastereoselectivity. This endo-peroxide rearranges into syn-(1R,2R:3S,4R)-diepoxide C-nucleoside, while by Et₂S-reduction followed by NEt₃ catalysis affords a spirocyclic C-nucleoside.