Isatin N-protected ketimines with nitromethane catalyzed by chiral binol linked monomeric macrocyclic Cu(II)–salen complex

Chiral Cu-1B generated in situ was used as an efficient catalyst for the synthesis of β-nitroamines in high yield (88%) with excellent enantioselectivity (ee up to 99%) at RT in absence of co-catalyst via asymmetric aza-Henry reaction of various isatin derived N-Boc ketimines with nitromethane. This catalytic system did not work well with other nitroalkanes under the above optimized reaction conditions. To examine this catalytic behaviour, quantum chemical DFT calculations were performed with the nucleophiles (CH₂NO₂^? and CH₃CHNO₂^?) for the conversion of 1a to 2a using macrocyclic Cu-1B complex. The DFT calculated results have shown that the reaction with CH₂NO₂^? is more favourable than the corresponding CH₃CHNO₂^?. The calculated activation barriers suggest that the reaction with CH₂NO₂^? is ～8.0?kcal/mol energetically favoured than CH₃CHNO₂^?. This catalytic protocol was further used to obtain chiral β-diamines (a building block for pharmaceuticals) at gram scale. In order to elucidate the reaction mechanism of asymmetric aza Henry reaction kinetic experiments were performed with different concentrations of the catalyst Cu-1B, nitromethane and 1g as the representative substrate. The reaction of isatin N-Boc ketimine was first order with respect to the concentration of the catalyst and the nitromethane but did not depend on the initial concentration of the substrate. A possible mechanism for the aza Henry reaction was proposed.     

Investigation of production routes for the 161Ho Auger-electron emitting radiolanthanide, a candidate for therapy

The radiolanthanide ¹⁶¹Ho (2.48 h) is a promising Auger-electron emitter for internal radiotherapy that can be produced with particle accelerators. The excitation functions of the ^natDy(p,xn)¹⁶¹Ho and ^natDy(d,x)¹⁶¹Ho reactions were measured up to 40 and 50 MeV respectively by using the stacked foil activation method and γ-ray spectrometry. The experimental data were compared with results of the TALYS code available in the TENDL 2011 library [1]. The main parameters of different production routes are discussed.     

Analysis of a Simplified Model of Rigid Structure Floating in a Viscous Fluid

Journal of Nonlinear Science - We study the interaction of surface water waves with a floating solid constraint to move only in the vertical direction. The first novelty we bring in is that we...     

Josephson effects in long superconducting bridges with variable thickness

We have studied the properties of long (L≈20μm) superconducting threads (Pb or Sn) formed by pulse electrical breakdown in monocrystalline silicon. These long bridges with variable thickness have well defined d.c. and a.c. Josephson effects in large temperature range (T/T_c?0.2 and 0.4 for Pb and Sn, respectively) and high magnetic fields (up to 0.14T for Pb at 4.2 K). In the whole temperature range, the critical current has linear temperature dependence, as for “ideal” Josephson junctions. The results are interpreted by coherent motion of vortices. Some interesting results about satellites of quasiparticle gap structures and the asymmetry of these structures with respect to the current direction are presented.     

The range of validity of the critical-velocity model in superconductors

From the distribution function of normal electrons in the energy gap of the superconductor, the influence of the electric current on the density of superconducting electrons is calculated and the maximum lossless velocityv _c of the electrons is determined. The value ofv _c limits also the range of validity of the critical-velocity model, calculated under the assumption of a rigidly pinned vortex lattice. The range of applicability of the critical-velocity model is shown to be restricted to the immediate vicinity of the upper critical field.     

Synthesis of a diazacrown ether containing polymers and formation of complexes with alkaline earth metals

We report the synthesis of a polymer that contains the diaza‐18‐crown‐6 moiety on the polymer main chain. Metal containing polymers were obtained when the respective barium or strontium complexes were used as monomers. These polymers emitted greenish blue light in solution, and the metal had little influence on absorption and emission energies. In the solid state, the position of the emission peaks was different probably due to a different degree of aggregation.