Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 70 , Issue 1
Showing 1-33 articles out of 33 articles from the selected issue
  • Shunichi Fukuzumi
    1997 Volume 70 Issue 1 Pages 1-28
    Published: 1997
    Released: June 11, 2006
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    Both thermal and photoinduced electron transfer reactions from one-electron reductants to various organic oxidants such as carbonyl compounds are catalyzed by the presence of acids and metal ions. The acceleration of rates of electron transfer is ascribed to the thermodynamic stabilization of products of electron transfer by the protonation or complexation with metal ions, which results in the positive shift of the reduction potentials of oxidants. In the case of Mg2+-catalyzed electron transfer reduction of p-benzoquinone derivatives, the formation of 1 : 1 and 1 : 2 complexes between semiquinone radical anion and Mg2+ is confirmed by the transient absorption spectra as well as by the ESR spectra. From the spectral change at different Mg2+ concentrations is determined the formation constant (K2) of the 1 : 2 complex. The K2 values of various semiquinone anions determined from the direct detection of the Mg2+ complexes agree well with those estimated from the kinetic analysis on the Mg2+-catalyzed electron transfer reactions. The direct spectroscopic detection of complexes between the semiquinone radical anions and Mg2+, combined with the kinetic analysis of the catalytic effects of Mg2+ on not only the electron transfer reactions but also on various reactions involving p-benzoquinone derivatives such as Mg2+-catalyzed Diels–Alder reactions of anthracenes with p-benzoquinone derivatives, provides a confirmative basis for delineating the catalytic mechanisms of Mg2+ on various types of reactions. A remarkable increase in the reactivity of the photoexcited states of carbonyl compounds in the electron transfer reactions is also found by the complexation with Mg2+. The photoexcitation of the Mg2+ complex results in strong fluorescence in contrast with the nonfluorescent excited states of uncomplexed carbonyl compounds. Thus, various redox reactions of carbonyl compounds via photoinduced electron transfer are made possible by the catalysis of metal ions which form complexes with carbonyl compounds. The fundamental concept and the scope of catalysis on electron transfer are reviewed in this account to provide some insight into the mechanistic viability.
  • Venkataraman Gurumani, Karuppiah Pandiarajan, Meenakshisundaram Swamin ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 29-35
    Published: 1997
    Released: June 11, 2006
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    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 (712) 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.
  • Ponnu Aravindan, Pichai Maruthamuthu, Periasamy Dharmalingam
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 37-45
    Published: 1997
    Released: June 11, 2006
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    The oxidation of benzidine by Ce(IV); the oxoanions MnO4 and Cr2O72−; peroxides, namely potassium peroxomonosulfate (KHSO5), peroxodisulfate (S2O82−) and H2O2; and halogens viz., Cl2, Br2, and I2, to the benzidine mono radical cation (benzidine•+) and further oxidation to the benzidine diradical cation (+•benzidine•+) by the above-mentioned oxidants, except for Br2 and I2, were investigated by a stopped-flow technique. The kinetics of both reactions, the formation and decay of benzidine•+, were monitored by following the absorption of the radical cation at λmax = 603 nm. The reactions were found to follow a total second-order kinetics, first-order each with respect to [benzidine] or [benzidine•+] and the [oxidant]. The effects of the pH and temperature on the formation and decay of benzidine•+ were also investigated. The kinetic and transition-state parameters were evaluated with a suitable reaction mechanism. The radical cation benzidine•+ was converted back to the parent compound, benzidine, by such reducing agents as sulfite (SO32−), thiosulfate (S2O32−), dithionite (S2O42−), and disulfite (S2O52−). The rate constants for these reactions were also estimated. The experimentally determined rate constants for the oxidative electron-transfer reactions were correlated theoretically using Marcus theory; the observed and calculated rate constants show good agreement.
  • Yasuo Kameda, Shun Suzuki, Hidekazu Ebata, Takeshi Usuki, Osamu Uemura
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 47-53
    Published: 1997
    Released: June 11, 2006
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    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.
  • Jacob Pacansky, Robert J. Waltman, Hajime Seki
    1997 Volume 70 Issue 1 Pages 55-59
    Published: 1997
    Released: June 11, 2006
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    Triphenylamine neutral and hole (radical cation) molecules are optimized by ab initio Hartree–Fock calculations at the 3-21G basis set. Modest changes in geometry are computed upon oxidation. The unpaired electron is 59% localized on the amine nitrogen atom. The energy barrier for the hopping process involving the electron transfer between a neutral and ionized (hole) triphenylamine is 0.15 eV. The vibrational mode that is primarily associated with the change in geometry upon hole formation is the C–N stretching mode.
  • Hiroshi Ichikawa, Hirotaka Kagawa
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 61-70
    Published: 1997
    Released: June 11, 2006
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    The constrained Hartree–Fock method provides quantum-mechanically acceptable wave functions of an arbitrary electronic structure without changing the molecular geometry. We have applied this method to the analysis of the behavior of π electrons in benzene finding that there are two types of resonance energy, simple resonance between double bonds and super-stabilization due to the topology of benzene, which were estimated as 54 and 168 kJ mol−1, respectively. According to our method, π electrons in benzene were found to have a propensity for uniform distribution. Namely, the D6h distribution of π electrons gives the minimum values concerning both the π-electronic and total energies, which are brought forth by lowering the kinetic energy of π electrons. The origin of delocalization of π electrons in benzene was attributed to relaxation of the kinetic-energy pressure of π electrons.
  • Ikuo Tokue, Takeyuki Kudo, Masaaki Kobayashi, Katsuyoshi Yamasaki
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 71-78
    Published: 1997
    Released: June 11, 2006
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    Photoemissions at 200—650 nm resulting from the He(23S) Penning ionization of CO2, CS2, OCS, N2O, C6F6, and C6F5H have been studied in the collision energy range of 120—210 meV using a crossed-beam method. The emission cross sections obtained for the excited parent ions were compared with the values measured at thermal energy. The band strengths for the vibrational bands of the OCS+() system are rather different from the values measured by the photoionization of OCS. The dependences of the emission cross sections for triatomic ions on the collision energy have been compared with those of the partial cross sections for the ion states obtained by Penning ionization electron spectroscopy, and the interaction potentials between He(23S) and the triatomic molecules correlating with the Penning ionization are discussed.
  • Yumin Li, Suehiro Iwata
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 79-88
    Published: 1997
    Released: June 11, 2006
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    A series of cyclic isomers of HNOx (x = 2—6) are examined with ab initio MO methods. All of these cyclic isomers have a ring comprised of one nitrogen atom and two to five oxygen atoms. They are classified under the following three types. Type A: NOx ring with an exo hydrogen bonded to a nitrogen; type B: NOx ring with an exo OH bonded to a nitrogen, and type C: NOx ring with an exo OOH bonded to a nitrogen. The geometry optimizations are carried out at the HF and MP2 levels of approximation with 6-31G** basis set, and the energies are evaluated at the MP4SDTQ approximation. We have failed to locate a five-membered ring HNOx at the MP2 level. The geometries and vibrational frequencies are discussed by comparing with the data of the related known stable molecules. The conformational preferences among the isomers are interpreted in terms of an intramolecular long-range hydrogen-oxygen interaction.
  • Katsuyoshi Yamasaki, Akihiro Watanabe
    1997 Volume 70 Issue 1 Pages 89-95
    Published: 1997
    Released: June 11, 2006
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    A new method of analysis for determining the rate constants of vibrational relaxation has been developed. Linearization of the equations of regression makes it possible to resolve the various problems and disadvantages of the conventional non-linear least-squares analyses. Not only the rate constants but also the relative detection sensitivities of different vibrational levels can be determined without information on photochemical parameters by which excitation spectra are usually corrected. Consequently, nascent vibrational distributions of the molecules produced in photolyses or chemical reactions can also be determined from the profiles recorded even under multiple collision conditions. The principles of the new method and how some advantage is offered are described, along with the comparison with the conventional analyses. Application of the method to practical schemes is also shown in detail.
  • Masatoshi Satozawa, Kimio Kunimori, Shigenobu Hayashi
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 97-105
    Published: 1997
    Released: June 11, 2006
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    13C and 1H MAS NMR spectra have been measured at room temperature for benzene and p-xylene adsorbed in H-ZSM-5, Na-, and H-type mordenites with different Si/Al2 ratios, H-Y, Na-Y, Na-X, and FSM-16 to study the dynamics of the guest species in the host materials. The second moments M2 evaluated from the SSB intensity in 13C CP/MAS NMR spectra were used to predict the motion of the guest species. Benzene molecules rotate about the C6 axis freely, and reorientation of the C6 axis takes place in H-ZSM-5. The para axis of p-xylene molecule is fixed in H-ZSM-5. The reorientations of the guest species become isotropic in the faujasite-type zeolites, Na-Y, H-Y, and Na-X. In FSM-16, translation diffusion takes place in addition to the isotropic rotation like in the liquid state. The mobilities of benzene molecules are in the following order, mordenite < H-ZSM-5 < Na-Y < Na-X < H-Y < FSM-16, while those of p-xylene molecules are in the following order. H-ZSM-5 < mordenite < Na-Y < Na-X ≈ H-Y < FSM-16. There is a good correlation between the pore size and the mobility of the guest species, with the exception of the mordenite/benzene systems.
  • Toshio Naito, Hayao Kobayashi, Akiko Kobayashi
    1997 Volume 70 Issue 1 Pages 107-114
    Published: 1997
    Released: June 11, 2006
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    The hybrid donor between bis(ethylenedithio)tetrathiafulvalene and -tetraselenafulvalene (ET and BETS, respectively) has been synthesized and the electrical properties together with the crystal structures of its cation radical salts investigated. All of the crystals studied by X-ray structural analysis turned out to have an orientational disorder at the donor site. Although some of the charge-transfer salts were found to be isostructural with the corresponding ET and/or BETS salts, not all of their electrical properties are parallel to them; some are similar, others are significantly different from those of the parent donor salts. Such a trend indicates that the effect of the disorder on the electrical behavior might not be always equal, and should depend on some factor(s) yet to be clarified.
  • Kiyofumi Murakami, Yuko Kimura, Masahiko Saito
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 115-121
    Published: 1997
    Released: June 11, 2006
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    Thermodynamics of the dimerization of 2-[(2-hydroxy-1-naphthyl)azo]-5-[(4-sulfonatophenyl)azo]benzenesulfonate in the presence of 0.05 mol dm−3 alkali metal cations and tetralkylammonium cations has been studied spectrophotometrically. From the dimerization constant and its temperature dependence, the values of standard enthalpy change and entropy change of dimerization have been calculated. The results show that both of them increase in the order of K+ < Li+ < Na+ < Rb+ < Cs+ and NH4+ < (CH3)4N+ < (C2H5)4N+ < (C3H7)4N+, and further, an enthalpy–entropy compensation relation with the compensation temperature of 300 K does hold. Dimer structure has also been examined using exciton theory. The angle between long molecular axes of monomers in the dimer lies in 43—44° for Na+, K+, Rb+, and Cs+, and is about 52° for Li+, but, that for tetralkylammonium cations has a tendency to increase with an increase in the size of the alkyl chain up to tetraethylammonium ion and somewhat decreases for tetrapropylammonium ion, i.e., 38° (NH4+) < 41° ((CH3)4N+) < 59° ((C2H5)4N+) > 46° ((C3H7)4N+). These results clearly show the participation of the cations in the thermodynamic and structural properties of the dimerization. By comparing the data with those in the absence of added salt, the results have been interpreted in terms of the condensation of cations around the dimer and the hydration structure of cations.
  • Hiroaki Kato, Yoshimasa Takahashi
    1997 Volume 70 Issue 1 Pages 123-127
    Published: 1997
    Released: June 11, 2006
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    A computer program, called SS3D, has been developed for the three-dimensional substructure searching of organic molecular structures. Our approach is based on a clique-finding algorithm that compares chemical graphs containing edges labelled with inter-atomic distances. The program allows one to specify some allowance of the distance for the geometrical matching of 3D-substructures; it also allows one to define some constraints for the query substructure or for the geometrical pattern to be used in the search. The details concerning the program are discussed and several illustrative examples are given.
  • Chun Qi Ma, Ke An Li, Shen Yang Tong
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 129-133
    Published: 1997
    Released: June 11, 2006
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    A method for the quantitation of proteins in aqueous solution involving the binding of bromopyrogallol red to proteins under acidic conditions has been developed. The binding of the dye to proteins is accompanied by an enhancement of Rayleigh light scattering at 332 nm; the scattering intensity is linear over the range 0.136—6.80 μg ml−1. The reaction is completed immediately after mixing dye and protein solutions, and the scattering signal is stable for at least 3 h. There are very few interference with the method, most of which can be minimized by dilution.
  • Hirochika Naganawa, Shoichi Tachimori
    1997 Volume 70 Issue 1 Pages 135-142
    Published: 1997
    Released: June 11, 2006
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    The hydration of nitric acid in dodecane was determined on the basis of the acid and water distribution between aqueous acid solutions and dodecane at 298 K. By analyzing the distribution data, mono- and decahydrate of nitric acid in addition to the anhydrous acid were found in dodecane. The solvent influence on the formation of the acid hydrates in dodecane was also compared with the results obtained in benzene.
  • Mitsutomo Tsuhako, Mayumi Danjo, Yoshinobu Baba, Masahiko Murakami, Hi ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 143-148
    Published: 1997
    Released: June 11, 2006
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    A synthetic method of a novel cerium(IV) bis(hydrogenphosphate) dihydrate, Ce(HPO4)2·2H2O, hereafter referred to as CeP·2H2O, has been established by the hydrothermal reaction of cerium(IV) oxide with phosphoric acid in an autoclave. The preparation of CeP·2H2O was significantly affected by the reaction conditions: the mixing ratio (P2O5/CeO2) of CeO2 and phosphoric acid, heating temperature and time, and water vapor pressure. The optimum condition for the preparation of CeP·2H2O was the mixing ratio of 1.5—2.0, heating temperature 175—200 °C, heating time 5 h, and water vapor pressure 5.0—7.0 atm.
    The results of X-ray powder diffraction, fluorescent X-ray analysis, differential thermal analysis and thermogravimetry (DTA-TG), IR spectrum, and phase transition showed that CeP·2H2O is a novel crystalline layered cerium(IV) phosphate having a interlayer distance d = 18.0 Å, longer than any layered phosphates (zirconium(IV), titanium(IV), and tin(IV) phosphates) so far reported.
    The reversible phase transition of CeP·2H2O occurred as follows, when exposed to various relative humidities:

    CeP·2H2O dissolved slightly in distilled water and hydrochloric acid, and much more in aqueous sodium hydroxide and aqueous ammonia. CeP·2H2O effectively adsorbed ammonia in an aqueous solution and ammonia gas.
  • Zhaomin Hou, Yugen Zhang, Yasuo Wakatsuki
    1997 Volume 70 Issue 1 Pages 149-153
    Published: 1997
    Released: June 11, 2006
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    The reaction of ytterbium(II) iodide (YbI2) with 4.5 equiv of hexamethylphosphoric triamide (hmpa) in tetrahydrofuran (thf) gave [Yb(hmpa)4(thf)2]I2 (1) as yellow crystals. A similar reaction of SmI2 with hmpa afforded black-purple [SmI2(hmpa)4] (2) after recrystallization from toluene. When 10 equiv of hmpa were used in the reaction with SmI2, [Sm(hmpa)6]I2 (3) was obtained as purple blocks. Complexes 13 have been structurally characterized by crystallographic studies. The structural data of these complexes satisfactorily explain the hmpa effects observed in SmI2-promoted reactions, and also provide a guideline for the use of HMPA in these reactions.
  • Habib Firouzabadi, Behzad Zeynizadeh
    1997 Volume 70 Issue 1 Pages 155-167
    Published: 1997
    Released: June 11, 2006
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    (1,4-Diazabicyclo[2.2.2]octane)(tetrahydroborato)zinc complex is a stable compound which has been used for the selective reduction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyloins and acyl chlorides to their alcohols and aldehydes in THF or CH2Cl2/hexane at room temperature or under reflux conditions.
  • Takashi Nakamura, Makoto Minato, Takashi Ito, Masako Tanaka, Kohtaro O ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 169-174
    Published: 1997
    Released: June 11, 2006
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    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.
  • Hiroshi Ogawa, Tetsuya Hosomi, Toshiaki Kosaka, Shigeyoshi Kanoh, Akih ...
    1997 Volume 70 Issue 1 Pages 175-187
    Published: 1997
    Released: June 11, 2006
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    A series of polyoxetanes were prepared by the cationic ring-opening polymerization of 4-(4-alkoxyphenylazo)phenyl 4-[7-(3-methyl-3-oxetanyl)-1,6-dioxaheptyl]benzoates using 0.08 molar amount of THF·BF3 in dichloromethane at 20 to 30 °C. Although the product polymers indicated GPC-average molecular weights of around 9000 to 23000, in most cases, they did not have an unimodal molecular weight dispersity. The liquid-crystalline mesophases of the polymers were examined by differential scanning calorimetry and polarized optical microscopy; these textures were observed due to nematic and/or smectic mesophases over a wide temperature range from about 250 °C to room temperature. The benzoate moiety, the longer p-substituted alkoxy tails, and the oxetane main chain play important roles in maintaining highly ordered, stable mesophases.
  • Kohtaro Osakada, Take-aki Koizumi, Takakazu Yamamoto
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 189-195
    Published: 1997
    Released: June 11, 2006
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    [RhClL2] (L = P(i-Pr)3) reacts with tris(2-phenylethyl)silane in pentane to give a dinuclear Rh(IV) complex, [LRh(H)2{μ-Si(CH2CH2Ph)2}2Rh(H)2L] (1), and several organic products including ethylbenzene, chloro{tris(2-phenylethyl)}silane, and tetrakis(2-phenylethyl)silane. Results of X-ray crystallography and NMR study of 1 indicate a symmetrical molecular structure containing two Rh(IV) centers which are bonded to each other through two bridging silylene ligands. [1, triclinic, space group with a = 12.886(4), b = 13.217(3), c = 10.388(3) Å, α = 104.78(2), β = 106.50(2), γ = 61.70(2)°, V = 1478 Å3, Z = 1, R = 0.073, Rw = 0.081 for 3930 reflections with I > 3σ(I) and 289 variables]. The initial reaction products contain mononuclear Rh(III) complexes, [RhCl(H)2L2] (2) and [RhCl(H) {Si(CH2CH2Ph)3}L2] (3), the latter of which is turned into 1 on further stirring. Reactions of tribenzylsilane and of tris(p-methylbenzyl)silane with [RhClL2] cause immediate separation of [RhL(R3Si)H(μ-Cl)2RhH(SiR3)L] (4: R = CH2Ph, 5: R = CH2C6H4Me-p). X-Ray crystallography of 4 has revealed the structure containing two Rh(III) centers with distorted trigonal bipyramidal coordination [4, monoclinic, space group P21/n with a = 11.513(3), b = 28.227(9), c = 20.883(5) Å, β = 94.14(2)°, V = 6769 Å3, Z = 4, R = 0.071, Rw = 0.066 for 4249 reflections with I > 3σ(I) and 637 variables]. A prolonged reaction of tribenzylsilane leads to formation of chlorotribenzylsilane.
  • Kazuaki Shimada, Norikazu Jin, Michiko Kawaguchi, Kumiko Dobashi, Yumi ...
    1997 Volume 70 Issue 1 Pages 197-206
    Published: 1997
    Released: June 11, 2006
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    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.
  • Hiroshi Kitajima, Katsuji Ito, Yuko Aoki, Tsutomu Katsuki
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 207-217
    Published: 1997
    Released: June 11, 2006
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    The newly introduced title compounds were found to be efficient chiral auxiliaries for the asymmetric Simmons–Smith cyclopropanation of allylic alcohols and for asymmetric addition of diethylzinc to aldehydes. For example, Simmons-Smith cyclopropanation of cinnamyl alcohol in the presence of N,N,N′,N′-tetraethyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamide (1b) proceeded with high enantioselectivity of 94% ee and addition of diethylzinc to benzaldehyde in the presence of N,N,N′,N′-tetraisopropyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamide (1e) proceeded with enantioselectivity of 99% ee. Although the reaction mechanism of these reactions is still nuclear, a monomeric seven-membered 2,2′-dihydroxy-1,1′ -binaphthyl-3,3′-dicarboxamide (1)–Zn complex is considered to be an active species which catalyzes the above reactions, on the basis of NMR experiments.
  • Pawel Kazmierczak, Lech Skulski
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 219-224
    Published: 1997
    Released: June 11, 2006
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    Oxidative anion metatheses in the crude title iodides and chlorides produced the corresponding pure hydrogensulfates, nitrates, tetrafluoroborates, triflates, tosylates, as well as bromides and chlorides (only from the iodides) in 54—86% yields. These procedures are easier and shorter than earlier methods. By using modified oxidative metatheses in the title iodides (in the presence of HBr or HCl) it was possible either to isolate, or to detect only, the intermediate dihaloiodates(I), [Ar2I]+[IX2] (X = Br or Cl). A complex Ph2I+Cl·1/2I2 was also obtained in 56% yield. Tetraethylammonium iodide was similarly converted into pure tetrafluoroborate or dibromoiodate(I) in 75 and 76% yields, respectively.
  • Ken-ichi Sato, Katsuhiko Suzuki, Miyuki Ueda, Yasuhiro Kajihara, Hiroy ...
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 225-230
    Published: 1997
    Released: June 11, 2006
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    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.
  • Kanji Kubo, Akira Mori, Hitoshi Takeshita
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 231-237
    Published: 1997
    Released: June 11, 2006
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    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.
  • Tsutomu Asano, Kohei Matsuo, Hitoshi Sumi
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 239-244
    Published: 1997
    Released: June 11, 2006
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    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 (>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.
  • Jun Tang, Hiroshi Shinokubo, Koichiro Oshima
    1997 Volume 70 Issue 1 Pages 245-251
    Published: 1997
    Released: June 11, 2006
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    The treatment of 4-benzyloxy-1-butyne with PhMe2SiMgMe in the presence of a catalytic amount of MnCl2 gave a monosilylated product, (E)-PhCH2OCH2CH2CH=CHSiMe2Ph, selectively after an aqueous workup. Meanwhile, the reaction of isoprene with PhMe2SiMgMe under manganese catalysis and the subsequent addition of iodomethane afforded 4-dimethylphenylsilyl-2,3-dimethyl-1-butene in good yield.
  • Kenkichi Sakamoto, Shinobu Tsutsui, Hideki Sakurai, Mitsuo Kira
    1997 Volume 70 Issue 1 Pages 253-260
    Published: 1997
    Released: June 11, 2006
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    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.
  • Masahiro Kuragaki, Masahiko Sisido
    1997 Volume 70 Issue 1 Pages 261-265
    Published: 1997
    Released: June 11, 2006
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    Highly efficient energy transfer from tryptophan units of an avidin tetramer to biotin-linked pyrenylalanine was observed. The energy transfer efficiency reached 85% when two of the four subunits were occupied with biotin-linked pyrenylalanine. The transfer efficiency vs. pyrenylalanine/binding site curve was simulated taking the distribution of the biotin derivatives among the four binding sites and the difference of Förster’s r0 values for polar and nonpolar tryptophans, into account. The results showed a qualitative agreement with the experimental data.
  • Shu Kobayashi, Mitsuhiro Moriwaki, Iwao Hachiya
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 267-273
    Published: 1997
    Released: June 11, 2006
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    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.
  • Eri Yoshida, Yasushi Okada
    1997 Volume 70 Issue 1 Pages 275-281
    Published: 1997
    Released: June 11, 2006
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    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.
  • Yasushi Tsurita, Keisuke Wada
    Type: Accounts
    Subject area: AI
    1997 Volume 70 Issue 1 Pages 283-291
    Published: 1997
    Released: June 11, 2006
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    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.
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