Shi Epoxidation:A Great Shortcut to Complex Compounds

Shi epoxidation provides an extremely powerful tool to access optically active epoxides,which undoubtedly belongs to one of the earliest and most successful org...     

Origin of visible-light-induced photocatalytic properties of S-doped anatase TiO2 by first-principles investigation

Electronic structures and optical absorption spectra of S-doped anatase TiO₂ are calculated by means of the first-principles pseudopotential total energy method. Electronic structure analyses demonstrate that isolated S 3p states which appear on the upper edge of the valence band cause the narrowing of the band gap of S-doped TiO₂. These changes of electronic structure exert great influence on the optical responses of S-doped TiO₂. Our results are in line with recent experimental observations that the redshift of optical absorption could be attributed to these isolated S 3p states on the upper edge of the valence band of S-doped TiO₂.     

Separation of the two enantiomers of naproxcinod by chiral normal-phase liquid chromatography

A normal-phase enantioselective high-performance liquid chromatographic method was developed for the enantiomeric resolution of naproxcinod, the most advanced cyclooxygenase-inhibiting nitric oxide donator of anti-inflammatory drugs designed for treatment of osteoarthritis. The enantiomers of naproxcinod were resolved on a Chiralpak AD-H (250 × 4.6 mm, 5 μm) column using a mobile phase system containing n-hexane and 2-propanol (95:5, v/v). The resolution between the enantiomers was found to be more than 2.0. The limit of detection and limit of quantitation of (R)-enantiomer were found to be 5 and 15 ng/mL, respectively, for 20 μL injection volume. The sample solution and mobile phase were found to be stable for at least 48 h. The final optimized method was successfully applied to separate (R)-enantiomer from naproxcinod and was proven to be reproducible and accurate for the quantitative determination of (R)-enantiomer in bulk drugs.     

Local and parallel finite element methods based on two-grid discretizations for the nonstationary Navier-Stokes equations

Numerical Algorithms - In this paper, some local and parallel finite element methods based on two-grid discretizations are proposed and investigated for the unsteady Navier-Stokes equations. The...     

A decomposition theorem on Euclidean Steiner minimal trees

The Euclidean Steiner minimal tree problem is known to be an NP-complete problem and current alogorithms cannot solve problems with more than 30 points. Thus decomposition theorems can be very helpful in extending the boundary of workable problems. There have been only two known decomposition theorems in the literature. This paper provides a 50% increase in the reservoir of decomposition theorems.     

Synthesis of 1-aminoisoquinolines via Rh(III)-catalyzed oxidative coupling

[RhCp*Cl(2)](2) can catalyze the oxidative coupling of N-aryl and N-alkyl benzamidines with alkynes to give N-substituted 1-aminoisoquinolines in high selectivity.     

Preparation of hydrophilic/hydrophobic porous materials

A novel porous material was designed and prepared in this work. A hydrophobic open-celled porous polystyrene (PS) was first synthesized via a concentrated emulsion polymerization of water in styrene. Subsequently the porous polystyrene was saturated with an aqueous solution of acrylamide (AM) and an initiator, which was subjected to another polymerization and the resulted polyacrylamide (PAM) penetrated in the cells and intercellular pores of the PS matrix. The PAM would change its volume according to the environmental humidity and thus adjusted the permeation of the material. The morphology, pore size distributions, water absorption, and vapor permeation of the materials were investigated.