Synthetic studies on quassinoids: a stereoselective construction of the picrasane skeleton

12β-Hydroxypicrasan-3-one, a compound having the correct relative stereochemistry of all the six ring-juncture chiral centers of the picrasane skeleton, was synthesized from a known tricyclic compound, using the orthoester Claisen rearrangement and lead tetraacetate oxidation as key reactions.     

Field dependence of uniform magnon energies in lamellar CoCl2 and CoBr2 by AFMR experiments

AFMR experiments in the frequency range 77<v<600 GHz and in the magnetic field range 0<H<75 kG on antiferromagnetic CoCl₂ and CoBr₂ single crystals at 4.2 K are reported. The waves propagate along the c axis of the crystals and the steady magnetic field is in the plane of the layers, which is also the easy plane of the spins.The influence of a rotation of the field in the easy magnetization plane is investigated, showing the existence of antiferromagnetic domains.The results of the field dependence of uniform magnon energies are reported in detail for the two compounds CoCl₂ and CoBr₂. In CoBr₂, the two magnon modes at zero field are non degenerate, their frequencies are v₁(0) = 60 GHzandv₂(0) = 675 GHz, and the field required for saturation is H_s⊥ = 74.2 kG.     

Synthesis of polyamideamines from 5-oxazolones

Polyamideamines with a sequence of two amide and one amine linkage in a main chain were synthesized from the polyaddition of 2-isopropylidene-4-alkyl-3-oxazolin-5-ones and primary diamines. The polyaddition reaction proceeded through 1,4-conjugate addition of an amine group to 3-oxazolin-5-one and subsequent ring opening of the intermediate addition product with another amine. Although aliphatic diamines gave oily polymers, xylylenediamines afforded amorphous solid polymers. The reduced viscosities and polymer melt temperature of the polymers were 0.05–0.12 and 90–130°C., respectively.     

Facile formation of water-insoluble cyclodextrin/Nafion composite films on solid surfaces

The water-insoluble poly-beta-cyclodextrin (poly-CD)/Nafion composite film was easily prepared by casting a mixed solution of poly-CD and Nafion onto substrate plates. FT-IR measurements showed that the 50/50 wt% poly-CD/Nafion composite film remained stable on the glass and quartz substrates after immersion in water for more than 3 h, while a pure poly-CD film was almost completely dissolved by immersion within 1 h. The film stability was also evaluated from the amount of p-nitrophenol (p-NP) inclusion in the film, which was determined from the decrease in UV-vis absorbance of the p-NP solution into which the film was immersed. The composition dependence of the inclusion amount showed that the film was stable up to 50 wt% CD, but became less stable with further increase in the CD concentration in the film. From the isotherms for the inclusion of p-NP and 1-naphthoate (1-Naph) into the film, the inclusion (stability) constants were determined to be 3.7x10(3) M(-1) and 1.9x10(2) M(-1), respectively. These results show that the selective inclusion of CD is retained after preparation of the composite film.     

Unusual Attractive Au–π Interactions in Small Diacetylene‐Modified Gold Clusters

It is well known that alkynes act as π‐acids in the formation of complexes with metals. We found unprecedented attractive Au–π interactions in diacetylene‐modified [core+exo]‐type [Au₈]⁴⁺ clusters. The 4‐phenyl‐1,3‐butadiynyl‐modified cluster has unusually short Au–C_α distances in the crystal structure, revealing the presence of attractive interactions between the coordinating C≡C moieties and the neighboring bitetrahedral Au₆ core, which is further supported by IR and NMR spectra. Such weak interactions are not found in mono‐acetylene‐modified clusters, which indicates that they are specific for diacetylenic ligands. The attractive Au–π interactions are likely associated with the low energy of the π* orbital in the diacetylenic moieties, into which the valence electrons of the gold core may be back donated. The [Au₈]⁴⁺ clusters show clear red‐shifts of >10 nm with respect to the corresponding mono‐acetylenic clusters in UV/Vis absorption bands, which indicates substantial electronic perturbation effects of the Au–π interactions.     

The Limits of Common Cause Approach to EPR Correlation

It is often argued that no local common cause models of EPR correlation exist. However, Szabó and Rédei pointed out that such arguments have the tacit assumption that plural correlations have the same common causes. Furthermore, Szabó showed that for EPR correlation a local common cause model in his sense exists. One of his requirements is that common cause events are statistically independent of apparatus settings on each side. However, as Szabó knows, to meet this requirement does not entail that different combinations of common cause events (e.g. meet and join in lattice-theoretic terminology) are statistically independent of measurement settings. This further condition is formulated in two ways. First, the apparatus settings are completely independent of such combinations. Second, the apparatus settings on each side are independent of such combinations. Does a common cause model which meets the former and the latter respectively exist? This problem is considered. In particular, the latter version is Szabó’s and Rédei’s open problem. Negative answers are given to both versions.