Copper-catalyzed anti-stereocontrolled ring-opening of azabicyclic alkenes with Grignard reagents

[Reaction: see text] The anti-stereocontrolled alkylative ring-opening reaction of azabicyclic alkenes is reported. N-(2-Pyridyl)sulfonyl azabenzonorbornadiene reacts with Grignard reagents in the presence of catalytic amounts of CuCN to afford, in good yields and excellent anti selectivity, the corresponding dihydronaphthalene-1-amines.     

Highlights of the Rh-catalysed asymmetric hydroformylation of alkenes using phosphorus donor ligands

Rhodium is currently the metal of choice to achieve high enantioselectivities in the hydroformylation of a relatively high variety of alkene substrates. The elucidation of the different steps of the catalytic cycle and the characterisation of the resting state, together with the discovery of several types of ligands that are able to provide high enantioselectivities, have made the rhodium-catalysed hydroformylation a synthetically useful tool. For years, ligands containing phosphite moieties such as diphosphites and phosphine–phosphites were considered the most successful ligands to achieve high enantioselectivies in this process. In fact, the phosphite–phosphine BINAPHOS 43 and its derivatives are even today the most successful ligands in terms of selectivity and scope. Recently however, diphosphine derivatives were shown to provide high levels of selectivity. It can consequently be concluded that the key to achieve high enantioselectivities is not the type the phosphorus function involved in the coordination to the metal, but the particular spatial arrangement of the coordinated ligand.     

Soluble transition-metal nanoparticles-catalysed hydrogenation of arenes

Over the last decade, the hydrogenation of arenes catalysed by soluble nanoparticles has attracted much interest from both academic and industrial research groups due to the milder conditions and the interesting selectivities achieved when compared to those obtained with classical heterogeneous catalysts. When substituted arenes are used as substrates in this reaction, the stereoselectivity is a key objective, and high levels of enantioselectivity are yet to be achieved.     

N-(2-pyridylmethyl)imines as azomethine precursors in catalytic asymmetric [3 + 2] cycloadditions

An efficient Cu(I)-catalyzed asymmetric [3 + 2] cycloaddition of N-(2-pyridylmethyl) imines has been developed. In the presence of a Cu(CH(3)CN)(4)PF(6)/bisoxazoline catalyst system, high levels of enantioselectivity (up to 97% ee) and moderate to high exo selectivity were achieved with a wide variety of substituted dipolarophiles, including maleimides, fumarates, fumarodinitrile, enones, and nitroalkenes. The reaction with unsymmetrically substituted dipolarophiles is completely regioselective.     

Value of high-performance liquid chromatographic analysis of amino acids in the determination of Panax ginseng radix extract effect in cultured neurons

The present research describes a reversed-phase high-performance liquid chromatographic (RP-HPLC) method that allows the determination of several amino acids in primary cultured cortical neurons of rats. The concentration of amino acids was determined by using pre-column derivatization with dansyl chloride and UV-diode array detection. Data show that Panax ginseng radix extract (GS) can modulate amino acid release in neurons. The levels of glutamate (Glu), aspartate (Asp), gamma-aminobutyric acid (GABA) and glycine (Gly) in the GS-treated groups were higher than in the non-treated groups dose-dependentwise. In this case, Glu and GABA were the most released amino acids (74.43% +/- 0.97 and 88.41% +/- 4.12 at ginseng dose 0.01 mg/ml after 1h from treatment, respectively). The values obtained in the determination of the analytical parameters (linearity, precision, limit of detection and accuracy) confirm the quality of the method. The average recoveries for intra and inter-day assay (n = 5) were 101.18 and 102.38 for Asp, 99.35 and 98.44 for Glu, 99.59 and 99.66 for Gly, and 100.06 and 100.37 for GABA. These data proved that the method yields accurate results, with RSD lower than 2.2%. The precision of the method was estimated on the basis of RSD of six injections at two different concentrations of amino acids. This technique is useful in studying the GS-mediated modulation of the dynamic equilibrium of amino acids and neurotransmission in neurons.     

Holographic reflection gratings in photopolymerizable solgel materials

The recording of holographic reflection gratings with a spatial frequency higher than 5400 lines/mm in photopolymerizable solgel materials is experimentally demonstrated. Diffraction efficiencies near 60% and a FWHM of 2.5 nm centered at 531.5 nm are achieved. Moreover, the effect of the energetic exposure is characterized at different recording intensities.