Solvent‐free synthesis of rotaxanes

Rotaxane‐type (macro)molecules are important materials in various fields of research, with many approaches for their synthesis having been developed over the past 30 years or so. When prepared in solution, the efficiency of interlocking pseudorotaxane complexes into the corresponding rotaxanes relies, to a great extent, on the affinity between the host and guest components; these interactions are not always sufficiently strong to overcome the deleterious effects of high reaction temperatures, competitive solvents, and low concentrations. Upon evaporating the solvent, however, the concentrations of the host and guest species increase significantly and, ultimately, their corresponding pseudorotaxanes can be generated with high efficiency in the solvent‐free residue. Furthermore, in the absence of the solvent, the influence of any disrupting byproducts (generated during the interlocking process) on the complexation equilibrium can also be largely reduced. Therefore, high synthetic efficiency and low consumption of solvents and energy can be expected when synthesizing rotaxanes under solvent‐free conditions. This mini‐review covers the main publications dealing with the solvent‐free syntheses of rotaxanes – those in which the interlocking step involves no solvent (or only a trace of it).     

New chiral morpholine-pyrrolidine ligands affecting asymmetric selectivity in copper catalyzed Henry reaction

In this study, several chiral diamine (35, 36, 37 and 39), triamine (24 and 25), diaminol (38, 42 and 43) and triaminol ligands (29 and 30) having chiral morpholine and pyrrolidine moieties conjugated constitutes, were prepared from commercially available (S)-2-amino-2-phenylacetic acid and (S)-proline. These ligands were complexed with copper (II) salt in situ and applied to asymmetric Henry reaction. Asymmetric addition of various structurally divergent aldehydes and nitromethane in the presence of 5?mol% of chiral ligand with CuCl₂ furnished corresponding β-nitro alcohol in good yields (up to 55–79%) with good enantioselectivity (up to 89%).     

Investigation of U(VI), Th(IV), and Eu(III) ions’ sorption behavior onto silica gel modified with anhydride

Journal of Radioanalytical and Nuclear Chemistry - Modification of silica gel by butanedioic anhydride (SiO2–BDAH) results in efficient adsorbents for removal of U(VI), Th(IV), and Eu(III)...     

Comparative pharmacokinetic study on three formulations of Astragali Radix by an LC–MS/MS method for determination of formononetin in human plasma

Astragali Radix (AR) is a widely used traditional Chinese medicine for healing the cardiovascular, liver and immune systems. Recently, superfine pulverizing technology has been applied to developing novel formulations to improve bioavailability of the active constituents in herbs, such as ultrafine granular powder of AR. In this study, a universal and sensitive quantitative method based on LC–MS/MS was employed for determining formononetin, the main flavonoid in AR, in human plasma for comparative pharmacokinetics of three oral formulations of AR. Formononetin and IS (quercetin) were extracted by ethyl acetate from human plasma and were separated on a C₁₈ column with a mobile phase consisting of acetonitrile and 0.1% formic acid. Positive‐ion electrospray‐ionization mode was applied in mass spectrometric detection. The quantitative method was validated with regards to selectivity, linearity, accuracy and precision, matrix effect, extraction recovery and stability, and was applied to comparing the pharmacokinetics of ultrafine granular powder (UGP), ultrafine powder (UP) and traditional decoction pieces (TDP) of AR after oral administration. The peak concentration and areas under the concentration–time curve of formononetin in UGP and UP were significantly higher than those of TDP. UGP and UP could significantly improve the bioavailability of AR in human compared with TDP after oral administration.     

The effect of polymerization conditions on crystalline of polybutene-1 catalyzed by metallocene catalyst

Polybutene-1 was synthesized stereoselectively with the precursorη5-(pentamethyl-cyclopentadienyl) tribenzyloxide titanium (Cp*Ti(OBz)3) and methylaluminoxane (MAO). The effects of polymerization conditions, trimethyl alumina (TMA) content in MAO and temperature on the crystalline and molecular weight of the products, and catalytic activity were investigated. The structural properties of the polybutene-1 were characterized with 13C NMR and WAXD.     

Mikheyev–Smirnov–Wolfenstein Effect¶for Linear Electron Density

When the electron density is a linear function of distance, it is known that the MSW equations for two neutrino species can be solved in terms of known functions. It is shown here that more generally, for any number of neutrino species, these MSW equations can be solved exactly in terms of single integrals. While these integrals cannot be expressed in terms of known functions, some of their simple properties are obtained. Application to the solar neutrino problem is briefly discussed. Received: 3 April 2000 / Accepted: 10 April 2000     

Total Synthesis of (±)-Iridolactone

A total synthesis of (±)-iridolactone ( 1 ) from bicyclo[2.2.1]ketone 6 is described. Trisubstituted cyclopentenoid aldehyde 7 is a key intermediate.     

On transverse momentum event–by–event fluctuations in string hadronic models

Transverse momentum event–by–event fluctuations are studied within the string–hadronic model of high energy nuclear collisions, LUCIAE. Data on non–statistical fluctuations in p+p interactions are reproduced. Fluctuations of similar magnitude are predicted for nucleus–nucleus collisions, in contradiction to the preliminary NA49 results. The introduction of a string clustering mechanism (Firecracker Model) leads to a further, significant increase of fluctuations for nucleus–nucleus collisions. Secondary hadronic interactions, as implemented in LUCIAE, cause only a small reduction of fluctuations. Received: 23 October 1998 / Published online: 11 March 1999     

Structural and magnetic properties of Mg(In2−xMnx)O4 system

We synthesized the Mn-doped Mg(In_2−xMn_x)O₄ oxides with 0.03?x?0.55 using a solid-state reaction method. The X-ray diffraction patterns of the samples were in a good agreement with that of a distorted orthorhombic spinel phase. Their lattice parameters and unit-cell volumes decrease with x due to the substitution of the smaller Mn³⁺ ions to the larger In³⁺ ions. The undoped MgIn₂O₄ oxide presents diamagnetic signals for 5 K?T?300 K. The M(H) at T=300 K reveals a fairly negative-sloped linear relationship. Neither magnetic hysteresis nor saturation behavior was observed in this parent sample. For the Mn-doped samples, however, positive magnetization were observed between 5 and 300 K even if the x value is as low as 0.03. The mass susceptibility enhances with Mn content and it reaches the highest value of 1.4×10⁻³ emu/g Oe (at T=300 K) at x=0.45. Furthermore, the Mn-doped oxides with x=0.06 and 0.2, respectively, exhibit nonlinear magnetization curves and small hysteretic loops in low magnetic fields. Susceptibilities of the Mn-doped samples are much higher than those of MnO₂, Mn₂O₃ oxides, and Mn metals. These results show that the oxides have potential to be magnetic semiconductors.