Photodimerization of benzene -photochromism of layered dithiacyclophane-

A novel cage compound was obtained by irradiation of a quadruple-layered dithiacyclophane and showed thermally reverse reaction.     

Synthesis of pyrimidinopurinophanes

Synthesis and structures of the title compounds 2a–d are described. In spite of non-parallel orientation of the two base rings, fairly large hypochromism was observed for 2a–d.     

The nature of europium ion in carbonate solution and polarographic determination of micro amounts of europium

The nature of the complex europium carbonate ion in concentrated carbonate solution was studied polarographically. A polarographic method for the determination of micro amounts of europium ion in the presence of diverse ions (and especially lanthanides) was developed.     

Effects of metal salts on polymerization. Part VII. Radical polymerization and spectra of vinylpyridine in the presence of cobaltous chloride

The radical polymerizability of vinylpyridines in the presence of cobaltous chloride was studied in DMF solution, and the results were correlated with the spectroscopic data obtained for methanol solution. In general, the behavior of vinylpyridine complexed with cobaltous chloride is qualitatively the same as that of zinc complexes reported previously. The rates of polymerization were enhanced by the addition of cobaltous chloride when 4-vinylpyridine(4-VP) or 2-methyl-5-vinylpyridine(MVP) was the monomer, whereas the polymerization of 2-vinylpyridine(2-VP) was retarded by cobaltous chloride. The monomer reactivity of all the vinylpyridines was also enhanced by complex formation as studied by copolymerization with styrene. The enhancement of reactivity of 4-VP complexed with cobaltous chloride is somewhat smaller than that of the corresponding zinc complex.     

Cross-chiral examinations of molecular enantioselective recognition by fast atom bombardment mass spectrometry: Host–guest complexations between chiral crown ethers and chiral organic ammonium ions

Using fast atom bombardment (FAB) mass spectrometry (MS), cross-chiral relationships were confirmed for the first time for the diasteromeric host-guest complexations between the chiral crown ether host (1) and the chiral organic ammonium ion guest (2) on the basis of the relative peak intensities (RPI). Both host–guest combinations (R, R, R, R) – 1, (R) – 2 and (S, S, S, S) – 1, (S) – 2 obviously provided larger RPI values than the combination of both (R, R, R, R) – 1, (S) – 2 and (S, S, S, S) – 1, (R) – 2 by a factor of 1.6 as an averaged value: 1.87 (n = 4)/1.16 (n = 4) = 1.6. These results are consistent with the expected stabilities of the host-guest complexations by CPK model examinations. Successfully observed cross-chiral examinations strongly suggest a potentially useful FABMS/RPI methodology for rapidly searching newly designed and synthesized crown ether-like host compounds with a higher degree of enantioselectivity.     

Effects of metal salts on polymerization. VI. Photo and thermally catalyzed polymerization of N-vinylimidazole in the presence of metal salts

Polymerization of 2-methyl-1-vinylimidazole (MVI) and 2-ethyl-1-vinylimidazole (EVI) was found to be markedly photosensitized in the presence of oxidizing metal salts such as UO₂(NO₃)₂, Ce(NH₄)₂(NO₃)₆, Hg(CH₃COO)₂, AgNO₃; non-oxidizing metal salts such as Zn^II did not act as photosensitizers. The interaction of monomer with a metal salt is discussed on the basis of infrared and electronic spectroscopy. This photopolymerization is very specific with respect to the kind of monomer. The polymerization of noncomplexing monomer (styrene) is not photosensitized by these metal salts. Consequently, photosensitized electron transfer between monomer and metal salt via complex formation is considered to be the most probable initiation mechanism. Cupric acetate and sodium chlorolaurate, which have been reported as efficient initiators for the polymerization of vinylpyridine and N-vinylcarbazole, respectively, act as linear terminators of growing radicals. The radical polymerizability of the zinc complex of MVI was studied by means of copolymerization with styrene. The reduction of the reactivity of MVI on complexing was explained by correlating with the spectroscopic observations. Because the polymerization system is heterogeneous, a detailed discussion was not possible.     

Pyrolysis of Dibenzyl Selenides to Bibenzyls

The formation of carbon-carbon bond by sulfur extrusion such as pyrolysis of cyclic sulfones is well known as an important synthetic method, especially for the synthesis of cyclophane framework.¹⁾ Little is known about selenium extrusion as the counterpart, though organoseleniums have been properly appreciated as a useful tool for manipulating a functional group.²⁾ Lardon reported that the thermal decomposition of dibenzyl diselenide led to a mixture of dibenzyl selenide and polyselenides.³⁾ In contrast, recent reports showed that at 210°C, heating bis(diphenylmethyl) diselenide resulted in ready selenium extrusion to 1,1,2,2-tetraphenylethane⁴⁾, and dianthrylmethyl mono- and diselenides to 1,2-dianthrylethane.⁵⁾ Therefore,- it is worthwhile to study the thermal behavior of dibenzyl selenide itself.     

Studies on the Syntheses of Multilayered [2. 2] Paracyclophanes

It is well-known that a number of double-layered compounds such as [2. 2]paracyclophane show anomalous physical and chemical properties due to the transannular π-electronic interaction between the stacked aromatic rings.²) Moreover, the interaction significantly increases with an increase of the layers as observed in a series of multilayered [2. 2]paracyclophanes³) and thereby it is of great interest to search a possibility of an organic semiconductor or its suitable model in them or their derivatives. However, such a study has been severely limited by great difficulty on the syntheses of the layered cyclophanes. While a number of synthetic methods have been developed for cyclophanes,²) only 1,6-Hofmann elimination method has so far been adopted to the preparation of multilayered [2.2]paracyclophanes.³) In practice, however, the yield is very low and becomes markedly poor with the increasing layers. Now we have studied some practical improvements on the preparation of multilayered [2.2]paracyclophanes.     

Synthesis,Structure, and Reactivity of Lewis Base Stabilized Plumbacyclopentadienylidenes

Plumbacyclopentadienylidenes, in which the lead atoms have divalent states and are coordinated by THF, pyridine and N‐heterocyclic carbene, were synthesized and characterized. The THF‐ and pyridine‐stabilized compounds can be regarded as rare examples of hypervalent 10‐X‐4 species. The equilibrium between the THF adduct and the free plumbacyclopentadienylidene was evidenced by spectroscopic analysis and theoretical calculations. The THF adduct in benzene converted into a plumbylene dimer, where one of the lead centers is coordinated by THF and the other lead atom is coordinated by a divalent lead atom, the dimer gradually decomposing into spiroplumbole. The THF adduct unexpectedly reacted with trifluoroborane and trichlorogallane to afford fluoroborole and chlorogallole, which are the first examples of non‐annulated fluoroborole and gallole, respectively.