A simple preparation of 1,3,5-triazine derivatives from 4-pyridones

The reaction of 4-pyridone or 4-quinolone with methyl or benzyl isocyanate in the presence of triethylamine or 1,1,3,3-tetramethylguanidine base gave the corresponding 1,3,5-triazine derivative (e. g., II) in a good yield via stepwise additions.     

Facile synthesis of quinone epoxides and 5,6-epoxy-4-hydroxy-2-cyclohexenones via the retro-diels-alder reaction

From commercially available quinoes, quinone epoxides and 5,6-epoxy-4-hydroxy-2-cyclohexenones were easily prepared through the retro-Diels-Alder reactions under rather mild conditions.     

Microgravimetric corrosion study of magnetron-sputtered Co-Cr-Mo and Ni-Cr-Mo alloys in an oxygen-containing atmosphere

A quartz crystal microbalance (QCM) has been used for in situ corrosion studies of magnetron-sputtered Co-Cr-Mo and Ni-Cr-Mo alloys, which are of great importance in various technical and medical applications. The corrosion monitoring has been performed in an oxygen-containing atmosphere and in NaCl solution. The alloys were deposited on quartz substrates by means of DC magnetron sputtering. X-ray photoelectron spectroscopy analysis showed that the composition of the deposits was similar to that of the magnetron-sputtering targets. X-ray diffraction revealed an amorphous structure of the sputtered deposits, while the casting alloys had a crystalline structure. The polarization resistance of sputtered alloys in NaCl solution was higher than the activity of conventional alloys, which implied a superior corrosion resistance of the sputtered deposits. Corrosion was initiated by supplying oxygen gas into a wet argon atmosphere and the QCM detected corrosion with nanogram resolution as the increase in mass. Corrosion currents were calculated from the mass versus time curves. The QCM appeared to be an effective tool for corrosive characterization of sputtered alloys in gaseous environments. A corrosion current calculation in solution was complicated by metal transfer to the liquid phase. Electronic Publication     

Absolute configuration of (−)-solanapyrone A

Absolute configuration of (?)-solanapyrone A was confirmed by the application of CD exciton chirality method to the dibenzoate derivative.     

Observation of doubly charged mercury cluster ions Hg n 2+, n=1-10 using secondary ion mass spectrometry

Mass spectra of doubly charged mercury clusters (m/z=30-1065) were investigated by secondary ion mass spectrometry. Positively charged ions were generated from an amalgam of mercury and silver by bombardment with a xenon ion beam and mass analysis by a grand-scale sector type mass spectrometer. Hg _n ²⁺, n=1-10 and Hg _n +, n =1- 5 were observed. Some doubly charged mercury clusters, (Hg _n ²⁺) survived at least for 0.1 ms.     

Anomalous octahedral distortion and multiple phase transitions in the metal-ordered manganite YBaMn2O6

By means of powder X-ray diffraction, powder neutron diffraction and transmission electron microscopy (TEM), we determined the crystal structures of a metal-ordered manganite YBaMn₂O₆ which undergoes successive phase transitions. A high-temperature metallic phase (T_c1=520 K<T) crystallizes in a triclinic P1 with the following unit cell: Z=2, a=5.4948(15) Å, b=5.4920(14) Å, c=7.7174(4) Å, α=89.804(20)°, β=90.173(20)°, γ=91.160(4)°. The MnO₆ octahedral tilting is approximately written as a⁰b⁻c⁻, leading to a significant structural anisotropy within the ab plane. The structure for T_c2<T<T_c1 is a monoclinic P2 (Z=2, a=5.5181(4) Å, b=5.5142(4) Å, c=7.6443(3) Å, β=90.267(4)°) with an a⁻b⁻c⁻ tilting. The structural features suggest a d_x²−y² orbital ordering (OO). Below T_c2=480 K, crystallographically inequivalent two octahedra show distinct volume difference, due to the Mn³⁺/Mn⁴⁺ charge ordering. The TEM study furthermore revealed a unique d_3x²−r²/d_3y²−r² OO with a modified CE structure. It was found that the obtained crystal structures are strongly correlated to the unusual physical properties. In particular, the extremely high temperature at which charge degree of freedom freezes, T_c2, should be caused by the absence of the structural disorder and by heavily distorted MnO₆ octahedra.     

Polarized ethylene. V. Synthesis of 1-substituted indolizine,pyrazolo[1,5-a]pyridine,and their related compounds using methoxyethylene derivatives

The reaction of pyridinium or isoquinolinium N-ylides with methoxy-substituted ethylenes gave the corresponding indolizine and pyrrolo[2,1-a]isoquinoline derivatives bearing acetyl, aroyl, cyano, ester group at the 1-position in one step. Pyrazolo[1,5-a]pyridine, pyrazolo[1,5-a]quinoline, and pyrazolo[5,1-a]isoquinolines were also synthesized in good yields from the corresponding aromatic N-imines and methoxyethylene derivatives.