Isoxazole --> benzisoxazole rearrangement promoted cascade reactions affording stereodefined polycycles

[reaction: see text] A new chemo-, regio-, and stereoselective cascade reaction features a novel isoxazole --> benzisoxazole rearrangement and affords highly functionalized, differentially protected compounds. The products of this reaction are directly converted to a number of complex, structurally diverse polycyclic molecules. These transformations highlight the unique chemistry inherent to readily prepared fused isoxazoles.     

Novel Zn/ZnI2-promoted cross-coupling of acrylic acid esters with arylaldehydes to alpha-aroyladipic acid esters

Cross-coupling of alkyl acrylates and arylaldehydes was achieved by treatment with metallic zinc and zinc(II) iodide in DMF, giving dialkyl alpha-aroyladipates in moderate yields.     

The Effect of Start-Up Conditions on Deactivation of Hydrotreating Catalyst for Heavy Residue with High Asphaltene Content

This article describes a pilot plant test, which was carried out to examine the effect of start-up operation conditions on catalytic performance in the commercial hydrotreating equipment. From the simulated several pilot tests, it was found that the operation conditions of this commercial equipment were very severe and the hydrogen supply to the catalyst active site was critical. When the heavy residue containing large amount of asphaltene was supplied at the start of run (SOR) in the commercial equipment, the permanent adsorption of carbonaceous deposit on the active site should cause leading the catalyst deactivation.     

Theory of ring formation in a reversible system: general solutions

The enumeration theory is extended in this work into a more general theory, taking back-reactions into consideration. The solutions may faithfully reproduce real processes from arbitrary starting points to a steady-state. Therefore, the presented theory includes the equilibrium theory by Jacobson-Stockmayer, the numerical solution by Gordon-Temple, and the irreversible theory by the present authors. The solutions are described first in general forms of transition probabilities {P}, and then explicitly with the aid of rate equations; simple proofs are given. The presented theory was applied to an experimental data: the distribution of cyclic species in poly(ethylene terephthalate). We shall show that agreement between theory and experiment is nearly perfect.AB model N ₀ Total number of units - V System volume - C ₀=N ₀/N _A ·V Initial concentration (N _A : Avogadro's number) - L _x AB type chain x-mer; (AB)_x - N _x Number of AB type x-mers - R _x Ring x-mer - N _Rx Number of ring x-mers - E Small molecule eliminated by bond-formation - N _E Number of small molecules eliminated by bond-formation - h _k Number of reacted functional units (f.u.) in statek - _k Number of reacted functional units (f.u.) in chains in statek - _k Total number of units in chains in statek - D=h _k /N ₀ Extent of reaction in statek - D ^*= _k / _k Extent of reaction in chains in statek - k _L Chain-propagation rate constant - k _Rx Cyclization rate constant of chain x-mers - k _B Bond breakage rate constant of chains - k _B,Rx Bond breakage rate constant of cyclic x-mers - <k _Rx > _k Mean cyclization rate constant in statek - g(x)=k _B,Rx /k _B Ring-opening factor of cyclic x-mers - P _Lx,k Probability that a chain x-mer will be formed in statek - {P} Set of transition probabilities per single jump in forward direction or reverse direction (see the text on individual transition probabilities) AB model M _A Total AA monomer unit number - M _B Total BB monomer unit number - M ₀=M _A +M _B Total particle number - _A,i =2M _A –h _i Unreacted A functional unit (f.u.) number in statei - _B,i =2M _B –h _i Unreacted B f.u. number in statei - _Ax Unreacted A f.u. number on x-mers - h _i Number of reacted A (or B) f.u. in statei - _i Number of reacted A (or B) f.u. in chains in statei - _A,i =2M _A –h _i + _i A f.u. number in chains in statei - _B,i =2M _B –h _i + _i B f.u. number in chains in statei - _i =2(M ₀–h _i + _i ) Total f.u. number in chains in statei - D=h _i /M ₀ Extent of reaction in statei - D _A ^* = _i / _A,i Extent of reaction of A f.u. in chains in statei - D _B ^* = _i / _B,i Extent of reaction of B f.u. in chains in statei - D ^*=2 _i / _i Extent of reaction in chains in statei - L _x (AA-BB)_x-1-AA type chain x-mer;x=1,2,3,... - L _x BB-(AA-BB)_x type chain x-mer;x=0,1,2,... - L _x (AA-BB)_x type chain x-mer;x=1,2,3,... - N _x Number of type x-mers - N _x Number of type x-mers - N _x Number of type x-mers     

Spectrometric determination of various metals by high-frequency plasma torch

Summary Several analytical conditions and detection limits of various metal elements were examined with regard to the determination of these elements by photoelectric spectrometry in the combination of high-frequency plasma torch apparatus and Ebert-type grating spectrometer (GE-340), using nitrogen as the carrier gas. All the calibration curves for the elements showed good linearity and standard deviations of calcium, zinc, tin, lead, and bismuth were in the range of 1.0–3.2%. It was found that, among the various elements, aluminium, zinc, tungsten, and lead, which are difficult to be determined by flame-spectrometric analysis, can be determined with good sensitivity and high precision by the present method.

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Zusammenfassung Zur spektrometrischen Bestimmung verschiedener Metalle wird eine Kombination von hochfrequenter Plasmaflamme und Gitterspektrometer vom Ebert-Typ (GE-340) benutzt, wobei Stickstoff als Trägergas dient. Alle Eichkurven weisen eine gute Linearität auf; die Standardabweichungen für Ca, Zn, Sn, Pb und Bi liegen im Bereich von 1,0 bis 3,2%. Al, Zn, W und Pb, deren Bestimmung nach der flammenspektrometrischen Methode Schwierigkeiten bereitet, können mit Hilfe des beschriebenen Verfahrens mit guter Empfindlichkeit und hoher Genauigkeit bestimmt werden.

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Dedicated to Prof. Dr. H.Kaiser on his 60th birthday.     

Polymorphic and pseudomorphic transformation behavior of acyclovir based on thermodynamics and crystallography

Acyclovir (ACV) has two polymorphs, anhydrate 1 and anhydrate 2, and two hydrates, 2/3 hydrate and dihydrate. The effect of polymorphic transformation of ACV on the temperature and humidity was evaluated by simultaneous XRD-DSC and vapor sorption analysis. Each crystal structure of ACV was analyzed by single crystal analysis and powder X-ray diffraction analysis. On the polymorphic and pseudomorphic transformation, anhydrate 1 did not directly transform to anhydrate 2, but transform through 2/3 hydrate and dihydrate due to relative humidity and temperature. According to the molecular packing for four crystals, there are two packing manners for purine moiety. Anhydrate 1, anhydrate 2, 2/3 hydrate and dihydrate were packed in parallel, anti parallel, mixture of parallel–anti parallel and parallel manners, respectively. Base on the packing manner of ACV, it can be seen why the phase transformation occurs with readily or with difficulty. The thermodynamic relation of anhydrate form 1 and form 2 was evaluated by DSC and microcalorimetry. It was found that these two forms are monotropic forms, with anhydrate form I is stable form and it transform to a new form 3 at 443.2 K.     

Crystal Structure of Europium C60 Compounds

Abstract

We have studied crystal structures of europium C₆₀ compounds by high resolution x-ray diffraction measurements. In the systematic synthesis of Eu _x C₆₀ for x (0 ≤ x ≤ 6), two stable phases appear at x = 3 and 6. Eu₆C₆₀ has a bcc structure, which is an isostructure to M ₆C₆₀ (M represents an alkali or alkaline earth metal). Eu₃C₆₀ has a superstructure derived by doubling the fcc pristine C₆₀ crystal along three principal axes. This superstructure comes from an ordering of cation vacancies, which is analogous to Yb_2.75C₆₀.