Catalytic Enantioselective Cyclopropylalkynylation of Aldimines Generated In Situ from α-Amido Sulfones

A convenient procedure of synthesis of N-carbamoyl-protected propargylic amines substituted with a cyclopropyl group from α-amido sulfones and cyclopropylacetylene is described. The reaction is catalyzed by a chiral BINOL-type zinc complex and provides the corresponding products in good yields and enantioselectivities.     

Studies on the Regioselectivity of Horner-Wadsworth-Emmons (Hwe) Reactions on 3,4-Enuloses. Further Evidence of Phosphonate-Phosphate Rearrangements Through Five Membered Cyclic Intermediates.

ABSTRACT

The Horner-Wadsworth-Emmons (HWE) reaction was performed on methyl 3,6-di-O-benzoyl-2-deoxy-α-D-glycero-hex-2-enopyranosid-4-ulose (1) with the potassium enolates of dimethyl [(methoxycarbonyl)methyl]phosphonate (2) or diethyl [(ethoxycarbonyl) methyl]phosphonate (3) under different conditions (metallic cation and solvent) in order to study regio- and stereochemical aspects of the reaction. In the presence of lithium ions, no reaction took place. When sodium enolates were employed, 1,2-addition was the main reaction in chelating solvents, whereas the 1,4-adduct is favoured in the less polar, non chelating toluene. Only 1,2-addition was observed with potassium enolates. Evidence of phosphonate-phosphate rearrangements through five membered cyclic intermediates is described.     

The Forwarding Indices of Random Graphs

A routing R of a graph G is a set of n(n ? 1) elementary paths R(u, v) specified for all ordered pairs (u, v) of vertices of G. The vertex-forwarding index ξ(G) of G, is defined by Where ξ(G, R) is the maximum number of paths of the routing R passing through any vertex of G and the minimum is taken over all the routings of G. Let G_p denote the random graph on n vertices with edge probability p and let m = np. It is proved among other things that, under natural growth conditions on the function p = p(n), the ratio Tends to 1 in probability as n tends to infinity.     

The electrochemistry of arylated anthraquinones in room temperature ionic liquids

Arylated anthraquinone derivatives of different sizes and different π‐basicities have been prepared, and the electrochemical behaviour of these substances has been studied on screen printed graphite electrodes in the three room temperature ionic liquids (RTILs), 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]), 1‐hexyl‐3‐methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) and 1‐octyl‐3‐methylimidazolium hexafluorophosphate ([C₈MIM][PF₆]). Half redox potentials for the first and second one electron reduction waves were identified, and the diffusion coefficient values were estimated from cyclic voltammetry measurements. The influence of the nature of the RTIL and of the substitution pattern of the anthraquinone on the solvodynamic radii were studied. A correlation of the reductive potentials with the corresponding Hammett constants of the substituents was tested. Copyright © 2013 John Wiley & Sons, Ltd.     

Design of the cold atom PHARAO space clock and initial test results

In this paper we describe the cold atom clock PHARAO, designed for microgravity operation. All elements of the PHARAO engineering model have been manufactured and delivered to CNES, the French space agency. We present the clock design, its main characteristics, and initial science operation. PHARAO is one of the main components of the Atomic Clock Ensemble in Space payload that is scheduled to fly on board the International Space Station in 2010. PACS 07.87.+v; 06.30.Ft; 95.55.Sh; 32.80.Pj     

Temperature dependence of ESR anisotropy in La7/8Sr1/8MnO3

We report X-ray diffraction, DC-susceptibility, electron spin resonance (ESR), and dilatometry measurements carried out on an La_7/8Sr_1/8MnO₃ single crystal. Thermal expansion was measured along different crystallographic axes using a three-terminal dilatometer. The sharp anomalies observed in the temperature dependence of Δl/l allowed us to locate the Jahn–Teller transition at T_JT=285(1) K. ESR experiments were carried out in the paramagnetic regime from 220 to 570 K, at 9.4 GHz. We measured the ESR line width ΔH_pp(T) with the magnetic field parallel to the crystallographic directions [1 0 0] and [0 0 1], referred to the orthorhombic (Pbnm) axes. We correlate the temperature dependence of ΔH_pp with the structural changes of the lattice.