Novel highly regioselective VO(acac)2/TBHP mediated oxidation of o-alkenyl phenols to o-hydroxybenzyl ketones

A novel mild methodology for the preparation of o-hydroxybenzyl ketones is described starting from o-alkenyl phenols and based on the VO(acac)(2)/TBHP (2 mol %/1.2 equiv) system. VO(acac)(2) first catalyzes the epoxidation of o-alkenyl phenols and then the rearrangement of the epoxyphenols to ketones via the selective benzylic C-O cleavage and 1,2 hydride migration. The protocol has also been applied to set up a useful and easy one-pot conversion of o-alkenyl phenols to benzo[b]furans by means of the sequential addition of TFA, after the generation of the intermediate o-hydroxybenzyl ketones.     

Renewable camphor-derived hydroperoxide: synthesis and use in the asymmetric epoxidation of allylic alcohols

Renewable enantiopure tertiary furyl hydroperoxide has been easily synthesized in two steps starting from low cost (+)-(1R)-camphor and it has been used in the asymmetric epoxidation and kinetic resolution of allylic alcohols (enantioselectivities up to 46%).     

Structural insight into [Fe–S2–Mo] motif in electrochemical reduction of N2 over Fe1-supported molecular MoS2

The catalytic synthesis of NH₃ from the thermodynamically challenging N₂ reduction reaction under mild conditions is currently a significant problem for scientists. Accordingly, herein, we report the development of a nitrogenase-inspired inorganic-based chalcogenide system for the efficient electrochemical conversion of N₂ to NH₃, which is comprised of the basic structure of [Fe–S₂–Mo]. This material showed high activity of 8.7 mg_NH3 mg_Fe⁻¹ h⁻¹ (24 μg_NH3 cm⁻² h⁻¹) with an excellent faradaic efficiency of 27% for the conversion of N₂ to NH₃ in aqueous medium. It was demonstrated that the Fe₁ single atom on [Fe–S₂–Mo] under the optimal negative potential favors the reduction of N₂ to NH₃ over the competitive proton reduction to H₂. Operando X-ray absorption and simulations combined with theoretical DFT calculations provided the first and important insights on the particular electron-mediating and catalytic roles of the [Fe–S₂–Mo] motifs and Fe₁, respectively, on this two-dimensional (2D) molecular layer slab.

A nitrogenase-inspired inorganic-based chalcogenide system containing [Fe–S₂–Mo] motif is developed for the efficient electrochemical conversion of N₂ to NH₃.     

On 2-transitive 3-nets

A 3-net is said to be 2-transitive if it admits a group of direction-preserving automorphisms fixing one of the transversal lines and acting 2-transitively on its points. We classify the 2-transitive finite 3-nets which do not admit a proper 2-transitive 3-subnet, except, possibly, for a subnet of order 2. The result is then extended under a weaker assumption.To Prof. Walter Benz and Prof. Jakob Joussen on their 60^th birthdaywork done within the activity of GNSAGA of CNR and supported by the Italian Ministry for Research and Technology.     

Monotone trajectories of multivalued dynamical systems

Summary We prove existence of ? monotone trajectories ? for a class of discrete and continuous systems sufficiently general to include problems of some interest in economic and biological theory. We prove existence of critical points which are Pareto minima. We study stability properties of Pareto minima. Entrata in Redazione il 7 settembre 1976. Sponsored in part by ARO Grant DAHC04-74-60012, and NSF MCS75-21868.     

Dielectric and thermal effects on the optical properties of natural dyes: a case study on solvated cyanin

The optical properties of the flavylium state of the cyanin dye are simulated numerically by combining Car-Parrinello molecular dynamics and linear-response time-dependent density functional theory calculations. The spectrum of the dye calculated in the gas phase is characterized by two peaks in the yellow and in the blue (green and violet), using a GGA-PBE (hybrid-B3LYP) DFT functional, which would bring about a greenish (bright orange) color incompatible with the dark purple hue observed in nature. Describing the effect of the water solvent through a polarizable continuum model does not modify qualitatively the resulting picture. An explicit simulation of both solvent and thermal effects using ab initio molecular dynamics results instead in a spectrum that is compatible with the observed coloration. This result is analyzed in terms of the spectroscopic effects of the molecular distortions induced by thermal fluctuations.     

Anchor group versus conjugation: toward the gap-state engineering of functionalized ZnO(1010) surface for optoelectronic applications

Molecular sensitization of the single-crystal ZnO (1010) surface through absorption of the catechol chromophore is investigated by means of density functional approaches. The resulting type II staggered interface is recovered in agreement with experiments, and its origin is traced back to the presence of molecular-related states in the gap of metal-oxide electronic structure. A systematic analysis carried out for further catecholate adsorbates allows us to identify the basic mechanisms that dictate the energy position of the gap states. The peculiar level alignment is demonstrated to be originated from the simultaneous interplay among the specific anchoring group, the backbone conjugation, and the lateral functional groups. The picture derived from our results provides efficient strategies for tuning the lineup between molecular and oxide states in hybrid interfaces with potential impact for ZnO-based optoelectronic applications.     

A catalytic asymmetric allylation of aldehydes with allyl trichlorosilane activated by a chiral tetradentate bis-sulfoxide

Chiral homoallylic alcohols are easily accessible by asymmetric allylation of aldehydes with allyl trichlorosilane in the presence of catalytic amounts of a chiral tetradentate bis-sulfoxide, as organocatalyst, whose synthesis is reported.     

Photoelectron Spectroscopy at the Graphene–Liquid Interface Reveals the Electronic Structure of an Electrodeposited Cobalt/Graphene Electrocatalyst

Electrochemically grown cobalt on graphene exhibits exceptional performance as a catalyst for the oxygen evolution reaction (OER) and provides the possibility of controlling the morphology and the chemical properties during deposition. However, the detailed atomic structure of this hybrid material is not well understood. To elucidate the Co/graphene electronic structure, we have developed a flow cell closed by a graphene membrane that provides electronic and chemical information on the active surfaces under atmospheric pressure and in the presence of liquids by means of X‐ray photoelectron spectroscopy (XPS). We found that cobalt is anchored on graphene via carbonyl‐like species, namely Co(CO)_x, promoting the reduction of Co³⁺ to Co²⁺, which is believed to be the active site of the catalyst.