Synthesis of 2-oxazolidinones by direct palladium-catalyzed oxidative carbonylation of 2-amino-1-alkanols

[reaction: see text] 2-Oxazolidinones 2 are obtained in excellent yields (up to 100%) and with unprecedented catalytic efficiencies (up to 2000 mol of product/mol of catalyst used) by direct PdI2/KI-catalyzed oxidative carbonylation of the readily available 2-amino-1-alkanols 1. Reactions are carried out in MeOH as the solvent at 100 degrees C using a 1/6/5 CO/O2/air mixture (60 atm total pressure at 25 degrees C).     

Physical and Chemical Characterization of Cellulose Based Textiles Modified by Periodate Oxidation

Conversion of dihydroxyl groups to dialdehyde by periodate oxidation is a useful method widely used in derivatization of cellulose to activate the polymer to further reactions as grafting polymerization. To investigate the cellulose behavior at different level of oxidation and to better understand the influence of the crystallinity on the effects induced by oxidative reactions on different cellulose materials, linen and cotton textiles have been oxidized with periodate solutions in different conditions. Oxidized cellulose samples have been characterized by several techniques: solid-state ¹³C NMR, Wide Angle X-Ray diffraction, and SEM. Moreover the mechanical properties of the untreated and oxidized yarns have been evaluated by means of tensile tests, the oxidation degree has been measured by means of the hydroxylamine hydrochloride method.     

Gauss–Lobatto to Bernstein polynomials transformation

The aim of this paper is to transform a polynomial expressed as a weighted sum of discrete orthogonal polynomials on Gauss–Lobatto nodes into Bernstein form and vice versa. Explicit formulas and recursion expressions are derived. Moreover, an efficient algorithm for the transformation from Gauss–Lobatto to Bernstein is proposed. Finally, in order to show the robustness of the proposed algorithm, experimental results are reported.     

Synthesis and mesomorphic properties of new liquid crystalline stilbene derivatives containing vinyloxyalkoxy chains

New liquid crystalline stilbene derivatives containing vinyloxyalkoxy chains 1 (n=5, 7, 9, 11) have been synthesised. Their mesomorphic properties have been studied by polarising optical microscopy and differential scanning calorimetry. It is interesting to note that even their alcohol precursors showed liquid crystalline behaviour. The effect of terminal alkoxy chain length and UV irradiation on the mesomorphic behaviour is discussed.     

Spatial versus temporal deterministic wave breakup of nonlinearly coupled light waves

We investigate experimentally the competition between spatial and temporal breakup due to modulational instability in chi((2)) nonlinear mixing. The modulation of the wave packets caused by the energy exchange between fundamental and second-harmonic components is found to be the prevailing trigger mechanism which, according to the relative weight of diffraction and dispersion, leads to the appearance of a multisoliton pattern in the low-dimensional spatial or temporal domain.     

A new catalytic synthesis of non-conjugated alkenynes

A new synthesis of alk-1-en-4-ynes catalyzed by nickel(0) complexes under mild conditions is described. The catalyst appers to be particularly sensitive to ligands; and to their ability to undergo dissociation from the metal.     

Photophysical and photobiological behavior of antimalarial drugs in aqueous solutions

This article describes the results of a combined photophysical and photobiological study aimed at understanding the phototoxicity mechanism of the antimalarial drugs quinine (Q), quinacrine (QC) and mefloquine (MQ). Photophysical experiments were carried out in aqueous solutions by stationary and time-resolved fluorimetry and by laser flash photolysis to obtain information on the various decay pathways of the excited states of the drugs and on transient species formed on irradiation. The results obtained showed that fluorescence and intersystem crossing account for all the adsorbed quanta for Q and MQ (quantum yield of about 0.1 and 0.9, respectively) and only for 24% in the case of QC, which has a negligible fluorescence quantum yield (0.001). Laser flash photolysis experiments evidenced, for QC and MQ, the occurrence of photoionization processes leading to the formation of the radical cations of the drugs. The effects of tryptophan and histidine on the excited states and transient species of the three drugs were also investigated. In parallel, the photoactivity of the antimalarial drugs was investigated under UV irradiation on various biological targets through a series of in vitro assays in the presence and in the absence of oxygen. Phototoxicity on 3T3 cultured fibroblasts and lipid photoperoxidation were observed for all the drugs. The photodamage produced by the drugs was also evaluated on proteins by measuring the photosensitized cross-linking of spectrin. The combined approaches were proven to be useful for understanding the mechanism of phototoxicity induced by the antimalarial drugs.     

Quantum signatures of breather-breather interactions

The spectrum of the quantum discrete nonlinear Schr?dinger equation, or boson Hubbard Hamiltonian, on a periodic 1D lattice shows some interesting detailed band structure, which may be interpreted as the quantum signature of a two-breather interaction in the classical case. This fine structure is studied using degenerate perturbation theory. We also present a modification to this model, which increases the mobility of bound states.