Novel [2 + 2] photocycloaddition-induced rearrangement of bichromophoric naphthalene-tethered resorcinol ethers

The first examples of sequential photocycloaddition-rearrangement reactions of naphthalene-tethered resorcinol ethers are described. Bichromophoric aromatic compounds with naphthalene and resorcinol ether moieties were irradiated in the presence/absence of a small amount of acid to give the corresponding cycloaddition-rearrangement products. From the determination of quantum yields, steady-state fluorescence spectral studies, and fluorescence lifetime measurements, the mechanism of this novel photoinduced multistep reaction was elucidated to involve the initial intramolecular exciplex formation, followed by the intramolecular [2 + 2] photocycloaddition between the two aromatic rings and the subsequent acid-catalyzed skeletal rearrangement of the resulting cyclobutane derivative leading to the final products.     

Two new phenylethanoid glycosides from the roots of Phlomis umbrosa

Two new phenylethanoid glycosides were isolated from the roots of Phlomis umbrosa. Their structures were elucidated by spectroscopic methods.     

Hydrostatic compression of the monoclinic form of polyethylene

Lattice constants of the monoclinic form of polyethylene under pressures up to 1.8 GPa at 298 K are investigated by x-ray diffraction. The thermal expansion from 100 K to 300 K at atmospheric pressure is also studied. The equation of state is calculated by Pastine's method, taking into account the zero-point vibration, and is compared with experimental results. The calculated results depend largely on the interatomic potential used and the limit of the interatomic distance for summation of the potentials. A change in the angle γ between the a and b axes results in an anisotropic change in the unit cell dimension with both pressure and temperature; the a and b axes change at nearly the same rate. The monoclinic form may have a higher density than the orthorhombic form at pressures above 1.0 GPa.     

Crystal structure of acetyl 29-methyl-29-methylidene-D:C-friedoolean-8-en-3beta-ol.

Acetyl 29-methyl-29-methylidene-D:C-friedoolean-8-en-3beta-o1 (2), derived from bryonolic acid (D:C-friedoolean-8-en-3beta-ol-29-oic acid) (1), was crystallographically analyzed. Rings A-E of 2 adopted chair, half-chair, half-chair, boat (with bow and stern at C-13 and C-16), boat (with bow and stem at C-19 and C-22) conformations, respectively. Good agreement was found between the structures from X-ray crystallography and that from MM2 calculations.     

Testing the PCAC prediction for the π0 lifetime

We compare the PCAC prediction based on the chiral anomaly for the π⁰ lifetime with a recent experiment. We find that the QED corrections are as large as 3%. After these corrections the experiment and the PCAC prediction disagree by 8.5 ± 2%. We estimate the corrections to the PCAC prediction. We find that reliably calculable corrections are not large enough to account for the discrepancy. However, contributions from the excited π⁰'s may be able to explain the difference.     

Hydrolysis of 4-cyano-1-ethoxypyrimido[1,6-a]benzimidazole: Formation of a ynaminonitrile and benzimidazolidines

The title compound 4 was hydrolyzed to a new type of ynaminonitrile 5 and benzimidazolidines 7 and 9 under acidic or basic conditions. Reaction mechanisms were proposed.     

An analysis of medium noise of Co-Cr double-layer films in perpendicular magnetic recording

The medium noise in perpendicular magnetic recording is discussed. The perpendicular recording mode was expected to prevent zig-zag walls around transitions, and the experimental result of low transition noise in Co-Cr media confirms this. Also, the main origin of the noise is concluded to be irregular clusters of grains in the film.     

A new facile synthesis of chelate reagent via 2-aminomethylpyridine-Co(III) complex: 2,3,5,6-tetra(2-pyridyl)pyrazine

2-Aminomethylpyridine $\text{(1)}$ readily reacted with Co(II) ion to give a chelate complex which reacted with oxygen to form, presumably, a μ-peroxodicobalt(III) complex or a Co(III)-$\text{(1)}$ complex, and finally it was transformed to 2,3,5,6-tetra(2-pyridyl) pyrazine.