Showing papers by "Chizuko Kabuto published in 2001"

Energy transfer luminescence of Tb3+ ion complexed with calix[4]arenetetrasulfonate and the thia and sulfonyl analogue. The effect of bridging groups

Abstract: New analogues of calix[4]arenetetrasulfonate (1) were prepared, in which the methylene bridges are replaced by S (2) and SO2 (3). The complexation ability of these calixarene ligands 1–3 toward Tb3+ ion and luminescence properties of the resulting complexes were examined. All the ligands formed complexes with lanthanide ions (Pr3+, Sm3+, Eu3+, Tb3+ and Dy3+), among which the Tb3+ complex exhibited strong energy transfer luminescence. The pH dependence of the luminescence intensity suggested that the analogues 2 and 3 possess higher complexation ability towards Tb3+ than the parent 1, which should be ascribed to the higher acidity of the phenolic OH groups as well as the coordinating ability of the bridging groups S and SO2. The composition of the complexes of 2 and 3 was determined to be Tb3+·2 and Tb3+·3 by a molar ratio method. The photophysical properties such as emission lifetimes (τ) and quantum yields (Φ) of the complexes were estimated. Both Tb3+·2 and Tb3+·3 gave comparable τ values (0.7 ms), which are larger than that of Tb3+·(1)2 (0.6 ms). Comparison of their lifetimes in D2O solution suggested that Tb3+·2 and Tb3+·3 have four to five coordinated water molecules responsible for quenching. On the other hand, complex Tb3+·2 gave the largest Φ value (0.15), whereas Tb3+·(1)2 and Tb3+·3 gave very close Φ values (0.12 and 0.13, respectively). The results of this study showed that thiacalix[4]arenetetrasulfonate 2 and the sulfonyl analogue 3 are promising candidates for the scaffold to construct luminescence devices from the viewpoint of the higher complexation ability and luminescent performance.

Unexpected reactions of an isolable dialkylsilylene with Haloalkanes

Abstract: Reactions of an isolable dialkylsilylene with dichloromethane and (chloromethyl)cyclopropane occur in solution to afford the double silylene insertion product and an unusual 5-silaspiro[4.4]nonane derivative, respectively. The activation of the carbon–chlorine bonds due to the complexation of haloalkanes with the silylene may facilitate the nucleophilic attack of another silylene under the present reaction conditions.

Generation of 1,3-Chalcogenaza-1,3-butadienes by Thermal Cycloreversion of 2,4,6-Trisubstituted 6H-1,3,5-Oxachalcogenazines

Abstract: 1,3-Thiaza- and 1,3-selenaza-1,3-butadienes bearing several substituents at the C-2 and C-4 positions were generated through thermal cycloreversion of 6H-1,3,5-oxathiazines or 6H-1,3,5-oxaselenazines, respectively, and the heterodienes were efficiently trapped by using acetylenic dienophiles. When 6H-1,3,5-oxathiazines or 6H-1,3,5-oxaselenazines were heated in the presence of nucleophiles, such as alcohols or thiols, the corresponding 1,4-adducts of the heterodienes with the nucleophiles were obtained in good yields. On the other hand, heating of 6H-1,3,5-oxathiazines or 6H-1,3,5-oxaselenazines in the absence of trapping agents afforded several products which originated from the in situ generated 1,3-chalcogenaza-1,3-butadienes; also the heterodienes were not isolated or observed directly as the monomeric forms at all.

[2 + 2] Cycloaddition reaction of cycloheptatriene with dichloroketene. A novel and efficient synthetic strategy for the synthesis of 2-hydroxyazulene

Abstract: The reaction of cycloheptatriene with dichloroketene, generated by the treatment of trichloroacetyl chloride with activated zinc in dry diethyl ether, affords 9,9-dichlorobicyclo[5.2.0]nona-2,4-dien-8-one 2 as a major product together with 3′,3′,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-2,4-diene-8,2′-oxetan)-4′-one 3. Structure 3 is elucidated by the X-ray crystallographic analysis of its partially reduced product. Lactone 3 exhibits [1,5] hydrogen-migration in the seven-membered ring to give 3′,3′,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-3,5-diene-8,2′-oxetan)-4′-one 7 without any decarbonylation. The reaction of 2 with diazomethane exhibits ring expansion of the four-membered ring to give 1,1-dichloro-3,3a,4,8a-tetrahydroazulen-2(1H)-one 8. 2-Hydroxyazulene 9 is successfully derived by the reaction of 8 with lithium chloride in good yield. The reaction of 8 with triethylamine exhibits dehydrochlorination to give 3-chloro-8,8a-dihydroazulen-2(1H)-one 10 in high yield. N-(Azulen-2-yl)pyrrolidine is also derived from either 9 or 10 in good yield.

Addition of HCl to a Base-Stabilized Hydrido(silylene)tungsten Complex and Reactivity of the Adduct toward LiAlH4

Abstract: The reaction of cis-Cp*(CO)2HW=SiPh2·Py (1, Py = pyridine) with HCl gave an adduct Cp*(CO)2H2WSiPh2Cl (2). Treatment of 2 with excess LiAlH4 afforded an anionic complex Li[cis-Cp*(CO)2HWSiHPh2] (4), and the same product was obtained by the reaction of 1 with LiAlH4.

Hydrogenation of Silyl-Substituted Alkynes Using Diimide: Application to the Synthesis of Saturated Sila-Macrocycles.

Abstract: The hydrogenation of bistrimethylsilylactylene, bis(trimethylsilyl)-1,3-diynes, and related silylalkynes giving the corresponding saturated compounds were achieved by using diimide prepared in situ from p-toluenesulfonyl hydrazide in diglyme. The present method was applicable to the synthesis of saturated 12- and 18-membered oligosilacycloalkanes.