Accelerated glycosylation under frozen conditions

O-Glycosylations using thiomethyl glycosides as donors were compared under both frozen and unfrozen conditions. In the presence of MeOTf as a promoter, enormous rate acceleration was observed when the glycosylation was conducted in p-xylene below its freezing point.     

Benzylation of hydroxy groups with tertiary amine as a base

The benzylation of hydroxy groups in the presence of tertiary amines is described. A mixture of an alcohol and a benzyl halide afforded the corresponding benzyl ether in good to excellent yields in the presence of diisopropylethylamine. The importance of solventless conditions was observed. The reaction showed high tolerance to many functional groups including benzoate, even at a reaction temperature of 150 °C. Sodium iodide was found to be an efficient catalyst to accelerate the reaction.     

Long-term stability of sulfated hydrous titania-based electrolyte for water electrolysis

Journal of Solid State Electrochemistry - The long-term stability in water was investigated for an inorganic proton conductor based on sulfated hydrous titania electrolyte in water electrolysis....     

High‐performance liquid chromatography separation of unsaturated organic compounds by a monolithic silica column embedded with silver nanoparticles

The optimization of a porous structure to ensure good separation performances is always a significant issue in high‐performance liquid chromatography column design. Recently we reported the homogeneous embedment of Ag nanoparticles in periodic mesoporous silica monolith and the application of such Ag nanoparticles embedded silica monolith for the high‐performance liquid chromatography separation of polyaromatic hydrocarbons. However, the separation performance remains to be improved and the retention mechanism as compared with the Ag ion high‐performance liquid chromatography technique still needs to be clarified. In this research, Ag nanoparticles were introduced into a macro/mesoporous silica monolith with optimized pore parameters for high‐performance liquid chromatography separations. Baseline separation of benzene, naphthalene, anthracene, and pyrene was achieved with the theoretical plate number for analyte naphthalene as 36 000 m^?1. Its separation function was further extended to cis/trans isomers of aromatic compounds where cis/trans stilbenes were chosen as a benchmark. Good separation of cis/trans‐stilbene with separation factor as 7 and theoretical plate number as 76 000 m^?1 for cis‐stilbene was obtained. The trans isomer, however, is retained more strongly, which contradicts the long‐ established retention rule of Ag ion chromatography. Such behavior of Ag nanoparticles embedded in a silica column can be attributed to the differences in the molecular geometric configuration of cis/trans stilbenes.     

Tetrahedral Oligothiophenes; Synthesis,X‐ray Analysis,and Optoelectronic Properties of Highly Symmetrical, 3D‐Branched Oligothiophenes

Tetrakis(bithienyl)methane and tetrakis(terthienyl)methane have been synthesized from tetrakis(2‐thienyl)methane by use of Suzuki–Miyaura coupling as a key reaction. Their trimethylsilyl (TMS) derivatives are also synthesized. X‐ray analysis reveals that each oligothiophene moiety tends to adopt anti‐conformations and show relatively small torsion angles between the adjacent thiophene rings. While the longest absorption maxima of these tetrakis(oligothienyl)methanes exhibit only a slight bathochromic shift compared to the corresponding linear oligothiophene derivative, tetrakis(bithienyl)methane and its TMS derivative exhibit an appreciable red‐shift in their fluorescence spectra. The intramolecular interaction between thienyl groups of tetrakis(2‐thienyl)methane is supported by DFT calculation.     

Synthesis and spectroscopic studies of CoII, NiII, FeIII and ThIV complexes derived from 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl

The synthesis of 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl (H2L) and its novel metal complexes with Co(II), Ni(II), Fe(III) and Th(IV) salts are reported. The ligand and its metal complexes have been characterized on the basis of analytical, conductance, spectral (IR, UV-vis, 1H NMR, mass) and magnetic susceptibility measurements. The M?ssbauer spectrum of the Fe(III) complex indicates a low-spin octahedral geometry around the Fe(III) ion. The IR and 1H NMR spectral data show that the ligand behaves in a dibasic bidentate fashion coordinating to two metal atoms through the two deprotonated naphthyl OH groups and acts in a dibasic tetradentate manner using both carbonyl oxygen's and the deprotonated naphthyl OH groups coordinating to two metal ions. Thermal studies (TGA, DTA) confirm the presence of solvents either inside or outside the coordination sphere and support the mechanism of the decomposition process. The value of [alpha]D20 for the ligand has been determined in DMSO.     

Regioselective protection of sugars catalyzed by dimethyltin dichloride

The first catalytic process for protection of hydroxyl groups in sugars has been developed. Highly regioselective protection was accomplished along with high chemical yield. The regioselectivity of the benzoylation was realized as an intrinsic character of sugars based on a stereorelationship among their hydroxyl groups. Furthermore, complete protection of alpha-methyl glucoside and beta-methyl xyloside was accomplished.     

Regulated Single‐Axis Rotations of a Carbonaceous Guest in a van der Waals Complex with an Entropy Cost

In a tight host–guest complex assembled solely by nondirectional van der Waals forces, unique motions of the guest, such as solid‐state inertial rotations, emerge. The regulation of dynamic motions is an important element to be explored for novel functions of such complexes, which may be seemingly difficult to achieve because of the nondirectionality of the assembling forces. A regulated, single‐axis rotation was made possible by choosing an appropriate shape of the guest in the tubular host. Specifically, an ellipsoidal guest was made to stand along a cylinder axis of the host, which consequently resulted in single‐axis rotations of the guest in the solid. The rotational frequency was considerably high for solid‐state rotations but was suppressed to 10 GHz, which was 1/20 of the isotropic rotation of a spherical guest. In‐depth kinetic analyses quantitatively revealed that the entropy cost was a determining factor that regulated the dynamics.     

Preparation and characterization of poly(l-phenylalanine) chiral stationary phases with varying peptide length

Three new chiral stationary phases with different lengths of l-phenylalanine peptide were prepared by solid-phase synthesis with tert-butoxycarbonyl (Boc)-l-phenylalanine on silica. The effect of phenylalanine peptide length on enantioselectivity was studied. The best separation of R/S-warfarin was achieved by the chiral stationary phase with intermediate peptide length. These stationary phases were found to exist mainly in alpha-helical conformation by using FT-IR spectra. The end-capping reagents for the N-terminus of the peptide were also evaluated.     

Effect of chemical crosslinking on mechanical and electrical properties of ultrahigh-molecular-weight polyethylene-carbon fiber blends prepared by gelation/crystallization from solutions

In an attempt to improve the mechanical property of polyethylene composite at high temperature, crosslinking of ultrahigh-molecular-weight polyethylene (UHMWPE) and carbon fiber (CF) blends was carried out by using dicumyl peroxide (DCP). The specimens were prepared by gelation/crystallization from solutions. The effect of chemical crosslinking on mechanical and electrical properties of UHMWPE/CF blends with composition of 1/0, 1/0.25, and 1/1 (w/w) were investigated in detail. Electrical conductivity and thermal mechanical properties of the blends with the 1/1 composition were greatly improved by incorporation of enough content of CF and adequate crosslinking network formation. Surprisingly, the Young’s modulus of the 1/1 blend reached 20 GPa at room temperature (20 °C). On the other hand, heat treatment at 135 °C played an important role for obtaining a high PTC effect for the UHMWPE-CF blend in which the PTC intensity reached 10⁷.