X‐ray crystallographic analysis and differential scanning calorimetry of two polymorphic forms of 2,6‐diphenyl‐1,4‐dithiin

2,6‐Diphenyl‐1,4‐dithiin 2 exists in the two polymorphic forms. The dithiin 2L , mp 62–63°C, was assigned as the metastable form, while the dithiin 2H , mp 79–80°C, was assigned as the stable form, mainly on the basis of differential scanning calorimetry (DSC) analysis. X‐Ray crystallographic analysis showed that the largest difference in the molecular structure between 2L and 2H is found in the coplanarity between the benzene ring and the double bond part of the dithiin ring; the benzene ring and the double bond are nearly coplanar for 2L , whereas these are far from being coplanar for 2H . © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:424–427, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20035     

Absorption-free calibration on X-ray fluorescence analysis of high-speed steel with glass bead preparation

This article describes a novel idea on preparation of a glass bead for X-ray fluorescence spectrometry, to determine alloyed elements in high-speed steel without any matrix correction. The quantification method using the glass bead is generally effective to reduce secondary X-ray absorption and enhancement (matrix effect) by coexisting elements in a sample. Although the glass bead is normally prepared based on a flux-to-sample ratio, the suggested method mainly controls an absolute amount of the sample in the glass bead to prevent from any interference with the matrix elements. As a result, the alloyed elements, except tungsten, in high-speed steels could be determined with high precision and accuracy, independent of the flux-to-sample ratio. However, the fluorescent X-ray intensity of tungsten Lα line (8.40 keV) was obviously influenced by the sample amount (iron content) in a glass bead; in this case, the Mα line (1.77 keV) could be employed alternatively.     

Synthesis of biodegradable thermoplastic elastomers from ε‐caprolactone and lactide

This article reports the synthesis and the properties of novel thermoplastic elastomers of A‐B‐A type triblock copolymer structure, where the hard segment A is poly(l ‐lactide) (PLLA) and the soft segment B is poly(ε‐caprolactone‐stat‐d ,l ‐lactide) (P(CL‐stat‐DLLA)). The P(CL‐stat‐DLLA) block with DLLA content of 30 mol % was applied because of its amorphous nature and low glass transition temperature (T_g = approximately ?40 °C). Successive polymerization of l ‐lactide afforded PLLA‐block‐P(CL‐stat‐DLLA)‐block‐PLLAs, which exhibited melting temperature (T_m = approximately 150 °C) for the crystalline PLLA segments and still low T_g (approximately ?30 °C) of the soft segments. The triblock copolymers showed very high elongation at break up to approximately 2800% and elastic properties. The corresponding d ‐triblock copolymers, PDLA‐block‐P(CL‐stat‐DLLA)‐block‐PDLAs (PDLA = poly(d ‐lactide)) were also prepared with the same procedure using d ‐lactide in place of l ‐lactide. When the PLLA‐block‐P(CL‐stat‐DLLA)‐block‐PLLA was blended with PDLA‐block‐P(CL‐stat‐DLLA)‐block‐PDLA, stereocomplex crystals were formed to enhance their T_m as well as tensile properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 489–495     

Total Synthesis of Aquayamycin

An efficient and practical total synthesis of aquayamycin has been accomplished. The highly oxidized and stereochemically complex tetracyclic ring system was constructed using three key reactions: 1) highly diastereoselective 1,2‐addition of C‐glycosyl naphthyllithium to a cyclic ketone, 2) indium‐mediated site‐selective allylation‐rearrangement sequence of naphthoquinone, and 3) diastereoselective intramolecular pinacol coupling. This synthetic strategy offers a novel and efficient pathway to prepare aquayamycin‐type angucycline antibiotics.     

High Pressure Study of Rotational Dynamics of Perylene and Sodium 8-methoxypyrene-1,3,6-trisulfonate in Imidazolium-Based Ionic Liquids

Rotation times of perylene and 8-methoxypyrene-1,3,6-trisulfonate (MPTS) in 1-alkyl-3-methylimidazolium tetrafluoroborate and 1-alkyl-3-methylimidazolium hexafluorophosphate under high pressure have been examined by means of time-resolved fluorescence anisotropy measurements. The isothermal compression of sample solutions by the application of high pressure can change the solvent viscosity alone over a wide range, allowing for an observation of the pure viscosity dependence of rotation times at a constant temperature (45 °C). Rotation times of both perylene and MPTS show a considerably nonlinear dependence on the solvent viscosity and a substantial deviation from the predictions of hydrodynamic and quasihydrodynamic theories, particularly at high pressures.     

Modeling for heat and mass transfer with phase change in porous wick of CPL evaporator

A mathematic model is developed to describe heat and mass transfer with phase change in the porous wick of evaporator of capillary pumped loop (CPL). This model with six field variables, including temperature, liquid content, pressure, liquid velocity, vapor velocity and phase-change rate, is closed mathematically with additional pressure relationships introduced. The present model is suitable to the numerical computation, as the established equations become comparatively easy to solve, which is applied to CPL evaporator. The numerical results are obtained and the parameter effects on evaporator are discussed. The study demonstrates that instead of an evaporative interface, there exists an unsaturated two-phase zone between the vapor-saturated zone and the liquid-saturated zone in the wick of CPL evaporator.     

PyBidine/Copper Catalyst: Asymmetric exo′‐Selective [3+2] Cycloaddition using Imino Ester and Electrophilic Indole

Electrophilic indoles having two electron‐withdrawing groups undergo nucleophilic attack at C2 and electrophilic functionalization at C3. This is the first enantioselective formal [3+2] cycloaddition using electrophilic indoles. The PyBidine/Cu catalyst smoothly promoted highly enantio‐ and exo′‐selective [3+2] cycloaddition using imino esters and 3‐nitroindoles. This reaction provides a method for the preparation of diverse and complex chiral pyrroloindoline compounds.