bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions of Molybdenocene and Tungstenocene Derivatives with Cobalt Carbonyls and the Related Compounds
Authors: Nakamura Takashi , Minato Makoto , Ito Takashi , Tanaka Masako , Osakada Kohtaro 
Published: June 2006

Abstract
Reactions of molybdenocene and tungstenocene derivatives [M(Cp)2(H)2], [M(Cp)2H(OTs)], or [{M(Cp)2H(μ-Li)}4] (M = Mo, W) with [Co2(CO)8] or [Co(CO)4]− gave [M(Cp)2H(CO)]+[Co(CO)4]− and [M(Cp)2(μ-H)(μ-CO)Co(CO)3] depending on the reaction conditions employed. These ionic heterobimetallic complexes were characterized by IR and NMR, as well as by X-ray diffraction analyses. A possible mechanism for the formation of the complexes is proposed.
Efficient Synthesis of Selenocarbonyl Compounds by Treating Carbonyl Compounds with Bis(1,5-cyclooctanediylboryl) Selenide
Authors: Shimada Kazuaki , Jin Norikazu , Kawaguchi Michiko , Dobashi Kumiko , Nagano Yumi , Fujimura Manabu , Kudoh Eiichi , Kai Tomonari , Saito Noboru , Masuda Jun-ichi , Iwaya Masaki , Fujisawa Hiroyuki , Aoyagi Shigenobu , Takikawa Yuji 
Published: June 2006

Abstract
Selenoaldehydes and selenoketones were generated in situ, by treating aldehydes or ketones, respectively, with bis(1,5-cyclooctanediylboryl) selenide; the resulting selenocarbonyl compounds were trapped with 2,3-dimethyl-1,3-butadiene to give the corresponding [4+2] cycloadducts. The treatment of amides, an ester, and ketones possessing bulky substituents with the reagent also afforded the corresponding selenoamides, a selenoester, and sterically protected selones, respectively, in modest yields. On the other hand, a similar treatment of cinnamaldehyde with the reagent gave the 2,3-dihydroselenophene derivative, which originated from a [4+2]-type self-dimerization of in situ generated 3-phenyl-2-propeneselenal.
Useful Intermediates, 3-C-Dichloromethyl Furanose Derivatives, for the Synthesis of Branched-Chain Functionalized Sugars
Authors: Sato Ken-ichi , Suzuki Katsuhiko , Ueda Miyuki , Kajihara Yasuhiro , Hori Hiroyuki 
Published: June 2006

Abstract
A few novel branched-chain functionalized sugars, which have important functions such as hydroxy, hydro, chloro, or azido at the quaternary carbon, were stereoselectively prepared in good yield via the same intermediary 3-C-,3-O-chloromethylene- or 3-C-dichloromethyl-1,2 : 5,6-di-O-isopropylidene-α-d-furanose derivatives.
Synthesis and Mercurophilic Properties of 2,2′-Oxybis(ethylenethio)ditropone and α-[2-(2-Troponylthio)ethyl]-ω-(2-troponylthio)oligo(oxyethylene)
Authors: Kubo Kanji , Mori Akira , Takeshita Hitoshi 
Published: June 2006

Abstract
The condensation reactions of 2-(p-tolylsulfonyloxy)tropone with 2,2′-oxydiethanethiol and its α-(2-sulfanylethyl)-ω-sulfanyloligo(oxyethylene) derivatives afforded 2,2′-oxybis(ethylenethio)ditropone and α-[2-(2-troponylthio)ethyl]-ω-(2-troponylthio)oligo(oxyethylene). Reflecting the acyclic nature of the polyethylene glycol moiety, they formed the complexes with various metal ions. Among them, mercury(II) salts were exclusively transported through a liquid membrane at least under the conditions used.
Effects of Solvent Fluctuations on the Rate of the Thermal Z/E Isomerization of N-Benzylideneanilines in a Highly Viscous Liquid Hydrocarbon
Authors: Asano Tsutomu , Matsuo Kohei , Sumi Hitoshi 
Published: June 2006

Abstract
The effects of the solvent viscosity on the thermal Z/E isomerization of three substituted N-benzylideneanilines were studied in a nonpolar aprotic solvent, 2,4-dicyclohexyl-2-methylpentane. By increasing the pressure to several hundred megapascals, the viscosity of the reaction system was raised high enough to retard the isomerization. The viscosity dependence of the observed rate constant was analyzed by assuming a two-step mechanism based on the two-dimensional reaction-coordinate model proposed by one of the present authors. The rate constant of this mechanism is given by 1/(kTST−1 + kf−1), where kTST represents the rate constant expected from the transition state theory, while kf (&gt;0) represents the part controlled by a solvent rearrangement during thermal fluctuations. The kf values were inversely proportional to a fractional power of the viscosity, in agreement with the theory. It was also found that, compared at the same temperature and viscosity, the kf values in the present solvent are larger than those in a polar aprotic solvent, glycerol triacetate, and in a polar protic solvent, 2-methyl-2,4-pentanediol, reported earlier.
Generation and Trapping of Bis(dialkylamino)silylenes: Experimental Evidence for Bridged Structure of Diaminosilylene Dimers
Authors: Sakamoto Kenkichi , Tsutsui Shinobu , Sakurai Hideki , Kira Mitsuo 
Published: June 2006

Abstract
Reduction of dichlorobis(diisopropylamino)silane and dichlorobis(cis-2,6-dimethylpiperidino) silane by alkali metals gave the corresponding bis(diisopropylamino)silylene and bis(cis-2,6-dimethylpiperidino)silylene, respectively. These were successfully trapped by toluene and benzene as well as by hydrosilane, olefin, and acetylene. As the first evidence for the existence of the bridged-dimer of the diaminosilylenes, we have found scrambling of the amino-substituents on a silicon atom during the simultaneous generation of two different bis(dialkylamino)silylenes in benzene. Diaminosilyenes generated thermally from the other new precursors designed here gave no evidence for the bridged dimer, due to the high temperature required for the generation.
The Catalytic Fries Rearrangement and o-Acylation Reactions Using Group 3 and 4 Metal Triflates as Catalysts
Authors: Kobayashi Shu , Moriwaki Mitsuhiro , Hachiya Iwao 
Published: June 2006

Abstract
Group 3 and 4 metal triflates (Sc(OTf)3, TiCl(OTf)3, Zr(OTf)4, and Hf(OTf)4) were found to be efficient catalysts in the Fries rearrangement of phenyl or 1-naphthyl acylates. It was also found that the o-acylation (direct acylation) reactions of phenols and 1-naphthols with acid chlorides proceeded smoothly in the presence of the triflates. Both reactions were successfully carried out using small amounts of the triflates (catalytically), and comparison of catalytic activities of these metal triflates in these reactions is discussed.
Living Radical Polymerization of Styrene in the Presence of 4-Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and Radical Transformation of the Resulting Polymer by Other Radicals
Authors: Yoshida Eri , Okada Yasushi 
Published: June 2006

Abstract
Radical polymerization of styrene was performed by benzoyl peroxide (BPO) as an initiator, in the presence of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (HTEMPO) at 95 °C for 3.5 h, and then continued at 125 °C for another designated period. The polymerization was found to proceed in the accordance with a living mechanism, because the molecular weight of the polystyrene was in proportion to the conversion and was in inverse proportion to the initial concentration of HTEMPO. Further, it was found that all the resulting polystyrene had the HTEMPO moiety at their chain ends and that the initial concentration of HTEMPO determined the molecular weight of the polymer produced, from 1H NMR analysis. The radical transformation of the HTEMPO-modified polystyrene by 4-methoxy-TEMPO (MTEMPO), was also performed. The transformation proceeded to give the polystyrene with MTEMPO moiety at the chain end, although the degree of the transformation decreased over time. It was found that decomposition of the MTEMPO-modified polystyrene obtained by the reaction occurred during the reaction.
Preparation of SiO2–ZrO2–Na2O Porous Glass Supports
Authors: Tsurita Yasushi , Wada Keisuke 
Published: June 2006

Abstract
A new method for preparing porous supports was investigated by heating a sol-gel-derived SiO2–ZrO2 and SiO2–TiO2 microspherical gel in the presence of NaCl. In the SiO2–ZrO2 system, the surface of the products comprised a sponge-like structure similar to the porous glasses manufactured by the phase-separation method. Their pore volume ranged from 1.48 to 3.18 cm3 g−1 and the surface area ranged from 10 to 48 m2 g−1. They contained a significant amount of Na2O, whereas the Cl content was less than 0.1 wt%. The alkaline durability was excellent, as was expected from the composition of SiO2–ZrO2–Na2O. On the contrary, a heat treatment of the sol-gel-derived SiO2–TiO2 microspherical gel, together with NaCl, caused crystallization of titania and silica, and the formation of glassy mixed oxide was not observed.
Conformational Studies of Some 1-Hetera-2,6-diphenylcyclohexan-4-one Oximes Using NMR Spectra-Evidence for Boat Form Contributions to trans-2,6-Diphenyl Systems
Authors: Gurumani Venkataraman , Pandiarajan Karuppiah , Swaminathan Meenakshisundaram 
Published: June 2006

Abstract
1H NMR spectra have been recorded for cis- and trans-2,6-diphenyltetrahydrothiopyran-4-ones (1 and 5), cis- and trans-2,6-diphenyltetrahydropyran-4-ones (2 and 6), 3-methyl- and 3-ethyl-2,6-diphenyltetrahydropyran-4-ones (3 and 4) and their oximes (7 — 12) at 270 MHz. For the oximes, 13C NMR spectra have also been recorded. The coupling constants suggest that the oximes 7, 8, 9, and 10, which have the phenyl groups in cis orientation, largely exist in chair conformations with equatorial disposition of the substituents. Analysis of the vicinal coupling constants of trans-2,6-diphenyltetrahydrothiopyran-4-one oxime (11) suggests that boat forms 11c and 11d must make significant contributions to it. Moreover, chair conformation 11a, which has the axial phenyl group in the syn-side, should be more populated than chair conformation 11b, which has the axial phenyl group in the anti-side. These conclusions are corroborated using 13C chemical shifts. The NOESY spectrum of 11 gives definite evidence for the contribution of 11c. The coupling constants of 12 suggest that the chair conformation 12a with axial phenyl group in the syn-side should be more populated than chair conformation 12b with the axial phenyl group in the anti-side. By analogy boat form should contribute to 12 also.
Conformational Studies Using Molecular Mechanics on Model Peptides with 1-Aminocycloalkane 1-Carboxylic Acid Residues
Authors: Rao Shashidhar N , Chan Ming Fai , Balaji Vitukudi N 
Published: June 2006

Abstract
Peptides with conformationally restricted 1-aminocyclopropane-1-carboxylic acid (Acc3) moieties were previously shown to exhibit preference for γ-turn structures in the solution phase and solid phase. We present conformational energy calculations on model compounds containing 1-aminocycloalkane carboxylic acid with 4, 5, and 6-membered rings using molecular mechanics methods. The low-energy models adopt conformations characteristic of a variety of regular structures, such as the α-helix, γ-turn, and polyproline-II-type three- and four-fold helices. The energetically most favored models adopt the γ-turn (2.27 helix) conformation in the model peptide of 1-aminocyclobutane-1-carboxylic acid (Acc4), similar to Acc3 peptides, while they adopt the α-/310-helical conformation (of either handedness) in the corresponding compounds with cyclopentane (Acc5) and cyclohexane (Acc6). The salient features of our investigations are qualitatively consistent with the crystal structures of peptide analogs containing Acc4, Acc5, and Acc6 and the previously reported solution phase and conformational studies on peptides containing Acc5. Our results have implications for the design of γ-turn and α-/310-helical peptidomimetics.
Surface Enhanced Raman Spectroscopic Study of 2- and 3-Bromothiophenes in Silver Hydrosol
Authors: Mukherjee Kana M , Misra T N 
Published: June 2006

Abstract
Surface enhanced Raman spectra (SERS) of 2- and 3-bromothiophene molecules in silver sol are compared with those of molecules in acetonitrile solution. The experimental results suggest that the 2-isomer is adsorbed on the metal surface through both the sulfur and the bromine atoms, with the thiophene molecular plane almost normal to the surface, whereas the 3-isomer is adsorbed principally through the sulfur atom. The Raman excitation profile of the molecules in the surface adsorbed state follows surface plasmon resonance frequency, reflecting the contribution of classical electromagnetic effect to SERS in silver sol. The observed “first layer effect”, i.e. maximum enhancement on a monomolecular layer formation on the metal surface, suggests charge transfer contribution to SERS of these molecules. Further, appearance of Ag–Br and Ag–S stretching modes in the SER spectra of 2-isomer indicates chemisorption of the adsorbate molecules on the metal surface.
Ion Association of Protonated Poly(vinylamine) and Poly(ethylenimine) with Poly(vinyl sulfate) and Dodecylbenzenesulfonate as Special Reference for Colloidal Titration
Authors: Hattori Toshiaki , Katai Kazuhito , Hattori Sadao , Kato Masanao 
Published: June 2006

Abstract
Ion association constants of two types of poly(vinylamine) and poly(ethylenimine) were determined from pH measurements of the polyamine/counter ion mixtures at an aqueous solution of the polymers (5 × 10−4 equiv mol dm−3). The results are discussed in terms of chemical structure (distance between reacting groups, and straight or branched chain), molecular weight, and ionic strength. The ion association at very low concentration protonated polyamines was promoted by the close location of amino groups. When the bound counter ions became close to each other, further ion association was inhibited by counter ions which had already bounded. From the colloidal titration of these polyamines, the stoichiometry could be discussed, especially under the conditions where all amino groups on the polymer are converted into ammonium ions. The results of the colloidal titration indicated that the stability constant for the ion association was drastically increasing near the equivalence point of the colloidal titration.
Solubility Product and Solubility of Cyclodextrin Inclusion Complex Precipitates in an Aqueous Medium
Authors: Sanemasa Isao , Wu Ji-Shi , Toda Kei 
Published: June 2006

Abstract
Cyclodextrins (CyD’s) have been precipitated as inclusion complexes with guest hydrocarbons from an aqueous medium, in which the guest hydrocarbon of interest was present in various concentrations. The solubility product constant of the CyD precipitate at 25 °C was determined by measuring the CyD concentration in the supernatant aqueous solution. Five model hydrocarbons were used as guests: hexane, cyclohexane, benzene, naphthalene, and biphenyl. The solubility products and the solubility in water of α-, β-, and γ-CyD inclusion complex precipitates with 36 varieties of guests were calculated based on the solubility of the guest hydrocarbon in water and the concentration of free CyD in the supernatant aqueous medium.
Cyclodextrin Precipitates with Normal Alcohols in an Aqueous Medium and Their Stability on Being Left Standing in Air
Authors: Sanemasa Isao , Wu Ji-Shi , Toda Kei 
Published: June 2006

Abstract
Cyclodextrin (CyD) precipitates with normal alcohols (guests, 1-butanol to 1-decanol) were prepared at 25 °C by introducing an alcohol vapor into an aqueous CyD solution and circulating it in a closed system. The guest/CyD molar ratio of the precipitates was measured immediately after preparation and after having been allowed to stand in air at room temperature for 30 or 40 d. Precipitates were obtained with alcohols higher than 1-pentanol for α-CyD, 1-hexanol for β-CyD, and 1-butanol for γ-CyD. The reason that CyD does not precipitate with lower alcohols could be explained in terms of the solubility product. There was a linear relationship between the apparent solubility (derived from the solubility product) of the CyD precipitates in water and the guest–CyD association constant. Upon drying in air, the guest/CyD molar ratio in the precipitates gradually decreased with days allowed to stand. In the cases of α- and γ-CyDs, the ratio remained constant after one week.
Spin Trapping of Phosphorus-Centered Radicals Produced by the Reactions of Dibenzoyl Peroxide with Organophosphorus Compounds
Authors: Sueishi Yoshimi , Miyake Yuzo 
Published: June 2006

Abstract
The reactions of dibenzoyl peroxide (BPO) with organophosphorus compounds have been studied by means of an ESR technique combined with spin trapping. The intermediate phosphorus-centered radicals were trapped by N-benzylidene-t-butylamine N-oxide (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The spin adducts with a characteristic hyperfine coupling constant (hfcc) due to a phosphorus atom were observed. From identification of trapped radicals, possible mechanisms of the reactions have been proposed. The hfccs due to β-hydrogen and phosphorus atoms exhibited a large temperature dependence for phosphoranyl–PBN spin adducts, while for phosphinyl–PBN spin adduct the dependence was small. Based on the P and H hfccs, the conformational positions of the adducts trapped by PBN and DMPO are discussed.
Antioxidant Activities of Phenothiazines and Related Compounds: Correlation between the Antioxidant Activities and Dissociation Energies of O–H or N–H Bonds
Authors: Yamamura Tatsuo , Suzuki Kyouichi , Yamaguchi Tatsuya , Nishiyama Tomihiro 
Published: June 2006

Abstract
The antioxidant activities of phenothiazines, carbazoles, and related diphenylamines were evaluated in the oxidation of tetralin at 60 °C and linoleic acid micelles in aqueous dispersion at 37 °C induced by an azo initiator. Phenothiazines were highly antioxidant in both systems. Although diphenylamine and carbazole were not good antioxidants, those having a hydroxy group as a substituent at the ortho or para position to the amino group were potently antioxidant. The antioxidant activity of o-hydroxydiphenylamine was much greater than that of other compounds in both systems due to a stabilization of the phenoxyl radical by delocalization of the unpaired electron to the p-type lone pair of the amino group. A semiempirical MNDO-AM1 calculation was applied to study hydrogen abstractions of antioxidants in the chain process of autoxidation. These results indicated that the rates of oxidation during the induction period correlated with the dissociation energies of the O–H or N–H bonds.
A New
α
-Iodination of Ketones Using Iodine-Ammonium Cerium(IV) Nitrate in Alcohol or Acetic Acid
Authors: Horiuchi C Akira , Kiji Shinji 
Published: June 2006

Abstract
The direct α-iodination of various ketones using iodine-ammonium cerium(IV) nitrate in acetic acid or alcohol gave the corresponding α-iodo ketones in high yields. The effect of cerium salt on the iodination of ketones, and the iodination of 5α-cholestan-3-one using several methods are also discussed. In the reaction of 3,3,5-trimethylcyclohexanone and unsymmetrical ketones, such as 2-hexanone and 2-heptanone, using methanol, ethanol, 1-propanol, and 2-propanol, the regioselective iodination product was obtained. In the case of bromination, the reaction of ketones with bromine and ammonium cerium(IV) nitrate also yielded the corresponding α-bromo ketones.
The Total Synthesis of a Glycosidase Inhibitor, Nagstatin
Authors: Tatsuta Kuniaki , Miura Shozo , Gunji Hiroki 
Published: June 2006

Abstract
A glycosidase inhibitor, nagstatin, has been synthesized from protected l-ribofuranose through the inter- and intra-molecular nucleophilic reactions of the imidazole moieties and the regioselective introduction of a carboxymethyl group.
Palladium-Catalyzed Cross-Coupling Reaction of Alkyltrifluorosilanes with Aryl Halides
Authors: Matsuhashi Hayao , Asai Satoshi , Hirabayashi Kazunori , Hatanaka Yasuo , Mori Atsunori , Hiyama Tamejiro 
Published: June 2006

Abstract
A cross-coupling reaction of alkyltrifluorosilanes with aryl halides was achieved using a catalytic amount of tetrakis(triphenylphosphine)palladium(0) and excess of tetrabutylammonium fluoride (TBAF) at 100 °C with high chemoselectitvity. Functional groups like nitro, ketone carbonyl, and formyl tolerated the coupling conditions. Because potassium(18-crown-6) alkyltetrafluorosilicates also underwent a cross-coupling reaction in the presence of an additional molar amount of TBAF, the active species of the coupling reaction was assumed to be pentacoordinate silicates. TBAF in excess was considered to be required for trapping the tetrafluorosilane produced in the catalytic cycle of the cross-coupling reaction.
Aromatic Allylsulfenylation with in Situ Generated Allylic Thiols under the Heck Conditions
Authors: Harayama Hiroto , Nagahama Takayuki , Kozera Toyohiro , Kimura Masanari , Fugami Keigo , Tanaka Shuji , Tamaru Yoshinao 
Published: June 2006

Abstract
A wide structural variety of S-allylic thiocarbamates 2 can be prepared in good yields by the rearrangement of O-allylic thiocarbamates 1 under three different conditions: thermal activation (neat, 120—150 °C), palladium(0) (25—65 °C), and palladium(II) catalysis (25—65 °C). Of the two possible regioisomers of unsymmetrical S-allylic thiocarbamates 2, those of higher thermodynamic stability can be prepared in high purity under either thermal activation or palladium(0) catalysis. Although the thermodynamically less stable regioisomers of 2 are, in general, hard to be prepared in high purity, some of them (e.g., 2d and 2h′) can be obtained with an exclusive or high selectivity by the catalysis of palladium(II). The stereoisomeric pair of 2j and 2j′ can be prepared selectively by the palladium(0)-catalyzed rearrangement of 1j and 1k, respectively. These reactions proceed with retention of configuration at the allylic stereocenters. S-Allylic (2) and S-alkyl thiocarbamates (7) undergo fragmentation to generate thiolates in the presence of inorganic bases (e.g., K2CO3, K2CO3·Et4N+I−) by heating in an aprotic solvent; the thus-formed thiolates react with aromatic iodides and vinyl bromides in the presence of palladium(0) complexes to furnish aryl and vinyl sulfides, respectively. A wide variety of aryl sulfides can be prepared in good yields irrespective of the kind of substituents and their substitution positions (o-, m-, p-) under conditions B [Pd(OAc)2, PPh3, K2CO3·Et4N+I−, dioxane, 100 °C]. Under conditions E [Pd(OAc)2, PPh3, Cs2CO3, dioxane, 100 °C], better yields result specifically for the sulfenylation of aromatic iodides bearing substituents having large Hammett σ constants.
The Short-Range Structure around Li+ in Highly Concentrated Aqueous LiBr Solutions
Authors: Kameda Yasuo , Suzuki Shun , Ebata Hidekazu , Usuki Takeshi , Uemura Osamu 
Published: June 2006

Abstract
Neutron diffraction measurements have been carried out on aqueous 10, 25, and 33 mol% LiBr solutions. The 6Li/7Li isotopic substitution technique was applied to determine the local structure around Li+ in these solutions. The least-squares fitting analysis was successfully adopted both for the observed Li+ difference interference function, ΔLi(Q), and for the Li+ distribution function GLi(r). The nearest neighbor Li+···O distance in the solutions was obtained to be 1.96 ± 0.02 Å, which agrees well with that reported in previous neutron diffraction studies. The average hydration number of Li+ decreases from ca. 6 for the 10 mol% LiBr solution to ca. 4 for the 25 mol% LiBr solution. The tetrahedral hydration structure around Li+ appeared to stay even in the 33 mol% LiBr solution. The Li+···Br− correlation was found at 3.4 Å in the 33 mol% LiBr solution. This value rather suggests the formation of the solvent-shared ion pair, Li+···D2O···Br−.
Synthesis and Properties of the Inner Salt, 3,3-Dipiperidino-3-propylium-1-dithioate: Adduct of 1,1-Dipiperidinoethene and Carbon Disulfide
Authors: Akimoto Keiichi , Masaki Kazuto , Nakayama Juzo 
Published: June 2006

Abstract
The nucleophilic addition of 1,1-dipiperidinoethene to carbon disulfide gives an inner salt, 3,3-dipiperidino-3-propylium-1-dithioate (8), in good yield. The inner salt 8 exists as an equilibrium mixture with its tautomer 3,3-dipiperidinodithioacrylic acid in the ratio of 9 : 1 in CDCl3 at 22 °C. The air-oxidation of 8 leads to bis(3,3-dipiperidinothioacryloyl) disulfide. The inner salt 8, prepared in situ, reacts with a wide variety of alkyl halides to provide a convenient synthesis of alkyl 3,3-dipiperidinodithioacrylates in one-pot.