Palladium-catalyzed isomerization of 1-hexene

The isomerization of 1-hexene over Pd(acac)₂ + BF₃OEt₂ and Pd(acac)₂ + PPh₃ + BF₃OEt₂ catalyst systems proceeds by the consecutive-parallel scheme. Tetracoordinate square-planar Pd hydrides bearing two vacant coordination sites are likely to be catalytically active species for the isomerization of hexene-1. This revised version was published online in June 2006 with corrections to the Cover Date.     

On asymptotic independence of the exit moment and position from a small domain for diffusion processes

If ξ(t) is the solution of homogeneous SDE in R ^m , and T _∃ is the first exit moment of the process from a small domain D _∃, then the total expansion for the following functional showing independence of the exit time and exit place is

The global stability conditions for solutions of nonstationary differential equations with instant impulsive effects in pseudolinear form

We obtained the sufficient conditions for the stability of solutions of a class of nonlinear differential equations with fixed instant impulsive effects in the Banach space. With the use of the Slyusarchuk’s condition and methods of the theory of operators in a partially ordered Banach space, the problem is reduced to the study of the stability of a linear system of second-order impulsive differential equations.     

Synthesis of Spirocyclic and Fused Isoxazoline Building Blocks

A highly efficient multigram synthesis of spirocyclic and fused isoxazoline building blocks is described. Isoxazoline-3-carboxylates were synthesized via a regioselective 1,3-dipolar cycloaddition reaction of 2-chloro-2-(hydroxyimino)acetate and carbo- or heterocyclic alkenes bearing endo- or exocyclic C=C double bonds, resulting in fused or spirocyclic isoxazolines, respectively. The preparation of up to 300 g of these compounds was achieved in a single run. The ester group of isoxazolines was then subjected to common synthetic transformations for the synthesis of corresponding building blocks, including alcohols, chlorides, azides, amines, aldehydes, carboxylic acids, amino acids and their derivatives, difluoromethyl-substituted compounds, and bicyclic γ-lactones. Additionally, a direct cycloaddition-based approach to the synthesis of aminoalkyl- and chloromethyl-substituted isoxazolines was proposed to improve their preparation. The described isoxazoline building blocks are expected to be valuable tools for drug discovery.     

Tb2–xNdxZn17–yNiy (x = 0.5, y = 4.83): a new intermetallic with a maximum disordered structure and its hydrogen storage properties

The ternary Tb_2–xNd_xZn_17–yNi_y (x = 0.5, y = 4.83) disordered phase belongs to the structural family based on the rhombohedral Th₂Zn₁₇ structure type. The structure is maximally disordered since all the sites are occupied by statistical mixtures of atoms. The Tb/Nd mixture of atoms occupies the 6c site (site symmetry 3m). The statistical mixtures Ni/Zn consisting of more Ni atoms are located in the 6c and 9d (symmetry .2/m) sites. In the following 18f (site symmetry .2) and 18h (site symmetry .m) sites are located Zn/Ni statistical mixtures which consist of more Zn atoms. Zn/Ni atoms form three-dimensional networks with hexagonal channels that fill statistical mixtures of Tb/Nd and Ni/Zn. The Tb_2–xNd_xZn_17–yNi_y compound belongs to the family of intermetallic phases capable of absorbing hydrogen. In the structure, there are three types of voids, namely, 9e (site symmetry .2/m), 3b (site symmetry m) and 36i (site symmetry 1), in which hydrogen can be inserted, and the maximum total absorption capacity can reach 1.21 wt% H₂. Electrochemical hydrogenation shows that the phase absorbs 1.03% of H₂, which indicates partial filling of the voids with H atoms.