Polarity inversion of donor-acceptor cyclopropanes: disubstituted δ-lactones via enantioselective iridium catalysis

The coupling of carbonyl electrophiles at the donor position of donor-acceptor cyclopropanes is described, representing an inversion of polarity with respect to conventional reactivity modes displayed by these reagents. Specifically, upon exposure of donor-acceptor cyclopropanes to alcohols in the presence of a cyclometalated iridium catalyst modified by (S)-BINAP, catalytic C-C coupling occurs, providing enantiomerically enriched products of carbonyl allylation. Identical products are obtained upon isopropanol-mediated transfer hydrogenation of donor-acceptor cyclopropanes in the presence of aldehydes. The reaction products are directly transformed to cis-4,5-disubstituted δ-lactones.     

Intramolecular [2+2] photocycloaddition of substituted isoquinolones: enantioselectivity and kinetic resolution induced by a chiral template

From simple to complex: Starting from easily accessible isoquinolones 1 (X=Br, OH), complex cyclobutane photoproducts such as compound 2 can be obtained with high enantioselectivity (88-96?%?ee) through the use of a chiral template. Compound 3, which was isolated in 53?%?ee starting from a racemic substrate, is the product of a unique, unprecedented kinetic resolution process.     

Inelastic proton scattering from Ba and Sm at 30 MeV

Measurements of the inelastic scattering of 30 MeV protons from ¹³⁸Ba and ¹⁴⁴Sm have been carried out with 7–10 keV energy resolution. Differential cross sections were measured for levels up through 3.4 MeV excitation energy. For most of these states J^π assignments are suggested on the basis of angular distributions distinctly characteristic of angular momentum transfer L = 2, 3, 4,or 6.     

Structural investigation of (CuI)0.45–(Ag2WO4)0.55 solid electrolyte using X-ray photoelectron and laser Raman spectroscopies

X-ray photoelectron spectroscopy (XPS) and laser Raman scattering (LRS) techniques have been employed to investigate the structure of amorphous (CuI)_0.45–(Ag₂WO₄)_0.55 solid electrolyte sample. XPS results reveal the presence of both Cu⁺ and Cu²⁺ ions whereas tungsten is found to exist only in the oxidation state of +6. The deconvolution of the O 1s spectrum into non-bridging and bridging oxygen atoms in conjunction with the laser Raman analysis tend to show that the amorphous (CuI)_0.45–(Ag₂WO₄)_0.55 solid electrolyte sample is composed mostly of octahedral WO₆ units that probably form [W₄O₁₆]⁸⁻ tetramer clusters, the existence of which is unique in the case of oxyhalide glasses.     

Conformation of solvent N,N-dimethylpropionamide in the coordination sphere of the zinc(II) ion studied by Raman spectroscopy and DFT calculations

Solvation structure of the zinc(II) ion in N,N-dimethylpropionamide (DMPA) was studied by Raman spectroscopy at varying temperature and by quantum mechanical calculations. No significant ion-pair formation was found for the Zn(ClO4)2 solution in the molality range m(Zn) < 1.5 mol kg(-1), and the solvation number of the zinc(II) ion was determined to be 4, indicating that 6-coordination of DMPA is sterically hindered. Interestingly, DMPA molecules are under equilibrium between planar cis and nonplanar staggered conformers, and the latter is more preferred in the coordination sphere, while the reverse is the case in the bulk. The DeltaG degrees , DeltaH degrees , and TDeltaS degrees values of conformational change from planar cis to nonplanar staggered in the coordination sphere were obtained to be -0.9, -8.5, and -7.5 kJ mol(-1), respectively. Density functional theory (DFT) calculations show that the planar cis conformer is more favorable than the nonplanar staggered one in the 1:2 cluster, as is the case for a single DMPA molecule and H(DMPA)+, indicating that there hardly occurs solvent-solvent interaction through the metal ion in the Zn2+-DMPA 1:2 cluster. On the other hand, the SCF energy of [Zn(planar cis-DMPA)4-n(nonplanar staggered DMPA)n]2+ (n = 0-4) decreases with increasing n, implying that the nonplanar staggered conformer is preferred in the solvate ion. It is thus concluded that solvent-solvent interaction through space, or solvation steric effect, plays a crucial role in the conformational equilibrium in the coordination sphere of the four-solvate metal ion.     

An electric bottle for colloids

Particle concentration is a dominant control parameter for colloids and other soft matter systems. We demonstrate a simple technique, "dielectrophoretic equilibrium," implemented as an "electric bottle," a planar capacitor in a larger volume. The uniform field in the capacitor traps particles in this force-free region at a higher density than in the zero field regions outside. We show how the technique measures the equation of state and we initiate and grow colloidal crystals. "Dielectrophoretic equilibria" enable the study of a complete concentration-dependent phase diagram from a single microscopic sample, obviating the previous need for preparing a large number of samples.