Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 71 , Issue 10
Showing 1-24 articles out of 24 articles from the selected issue
  • Hideki Sugimoto, Toshihiko Nagayama, Sachihito Maruyama, Shuhei Fujina ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2267-2279
    Published: 1998
    Released: June 05, 2006
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    A new dinucleating ligand containing a sterically bulky imidazolyl group, Ph-Htidp (N,N,N′,N′-tetrakis[(1-methyl-4,5-diphenyl-2-imidazolyl)methyl]-1,3-diamino-2-propanol), and its μ-alkoxo-diiron(II) complexes [Fe2(Ph-tidp)(RCO2)](ClO4)2, (RCO2 = C6H5CO2 (1), C6F5CO2 (2), CF3CO2 (3), and C2H5CO2 (4)), were synthesized. The structure of complex 1 was determined by X-ray crystallography. Complex 1 crystallizes in the monoclinic space group P21/c with a = 13.464(2), b = 19.223(4), c = 31.358(4) Å, β = 92.84(2)°, and Z = 4. The complex has a doubly-bridged structure with μ-alkoxo of Ph-tidp and μ-benzoate; the two iron centers have a distorted five-coordinate structure with N3O2 donor set. All the complexes showed fairly good reversible oxygenation below −30 °C in CH2Cl2, which was monitored by UV-vis and NMR spectroscopies, and dioxygen up-take measurements. Introduction of 4,5-diphenyl substituents into 2-imidazolyl group stabilized the μ-peroxo diiron species against irreversible oxidation, just as introduction of 6-methyl substituent into 2-pyridyl group did. Phenyl substituents appear to weaken the electron donor ability of a dinucleating ligand to stabilize divalent oxidation state of iron and to form a hydrophobic cavity for a O2 binding site, which would suppress the irreversible oxidation and facilitate the reversible oxygenation. Dioxygen affinities of the Ph-tidp and Me4-tpdp diiron(II), and the tpdp and bpmp dicobalt(II) complexes were measured, [Fe2(Me4-tpdp)(RCO2)]2+ (RCO2 = C6H5CO2 and RCO2 = CF3CO2) and [Co2(L)(RCO2)]2+ (L = tpdp, RCO2 = CH3CO2, and L = bpmp, RCO2 = C6F5CO2, and CF3CO2), where Me4-tpdp, tpdp, and bpmp are N,N,N′,N′-tetrakis[(6-methyl-2-pyridyl)methyl]-1,3-diamino-2-propanolate, N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-diamino-2-propanolate, and 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenolate, respectively. Within a series of the Ph-tidp diiron(II) complexes, dioxygen affinity is well correlated with electron donor ability of bridging carboxylates (1 (C6H5CO2) > 2 (C6F5CO2) > 3 (CF3CO2)). In contrast to the above trend, dioxygen affinities of the Ph-tidp complexes are lower than those of the Me4-tpdp complexes, although electron donor abilities of the Me4-tpdp complexes are weaker than those of the Ph-tidp complexes. Significant enhancement of dioxygen affinity was observed for both iron and cobalt complexes with 2,6-bis(aminomethyl)phenolate bridging skeleton compared to the complexes with a 1,3-diamino-2-propanolate bridging one. Thermodynamic study suggested that the observed enhancement is mainly attributable to a favorable entropy effect along with a steric effect.
  • Taisuke Hamada, Masaya Tsukamoto, Hiroshi Ohtsuka, Shigeyoshi Sakaki
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2281-2291
    Published: 1998
    Released: June 05, 2006
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    Photoexcited *[Ru(bpy)3]2+ is oxidatively quenched by methylviologen (MV2+) and 1,1′-bis(2-carboxyethyl)-4,4′-bipyridinium (BCEBP2+) with a similar rate constant at pH 2.2; kqobs = 1.48 × 109 and 1.58 × 109 mol−1 dm3 s−1 (30 °C) for MV2+ and BCEBP2+, respectively. However, *[Ru(bpy)3]2+ is much more slowly quenched by MV2+ than by BCEBP0 at pH 5.0, where the superscript “0” represents that BCEBP is neutral; kqobs = 1.01 × 109 and 1.74 × 109 mol−1 dm3 s−1 for MV2+ and BCEBP0, respectively. The reverse electron-transfer reaction between [Ru(bpy)3]3+ and one-electron-reduced ·BCEBP+ (krevobs = 3.33 × 109 mol−1 dm3 s−1) proceeds slightly more rapidly than the reaction between [Ru(bpy)3]3+ and ·MV+ (krevobs = 2.80 × 109 mol−1 dm3 s−1) at pH 2.2 (30 °C), while the former reaction (krevobs = 5.85 × 109 mol−1 dm3 s−1) proceeds 2-times as rapidly as the latter reaction (krevobs = 2.74 × 109 mol−1 dm3 s−1) at pH 5.0. These differences at pH 5.0 between MV2+ and BCEBP0 are interpreted in terms of charge effects on the diffusion and diffusional dissociation of an exciplex and an encounter complex. The electron-transfer reactions in the exciplex and the encounter complex have been analyzed according to Marcus theory. The difference in an electronic coupling matrix element (Hrp) between MV2+ and BCEBP2+ or 0 is discussed in terms of the charge effects and steric effects.
  • Kiyofumi Murakami
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2293-2298
    Published: 1998
    Released: June 05, 2006
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    Binding of sodium 4-(2- or 4-hydroxy-1-naphthylazo)benzenesulfonate and sodium 4-[4-(amino or dialkylamino)phenylazo]benzenesulfonate (alkyl: methyl, ethyl, or butyl) to hen egg white lysozyme has been studied by an equilibrium dialysis method at pH = 7.0 (0.1 mol dm−3 phosphate buffer) and 25 °C. In the case of the (2- or 4-hydroxy-1-naphthylazo)benzenesulfonate system, a single cooperative binding stage has been observed with a maximum binding number of 10. In the case of the 4-[4-(dialkylamino)phenylazo]benzenesulfonate systems, two cooperative binding stages have been observed for the dyes having alkyl groups longer than a methyl group. The maximum binding numbers of the first stage are 14 and 13 for 4-[4-(diethylamino)phenylazo]benzenesulfonate and 4-[4-(dibutylamino)phenylazo]benzenesulfonate, respectively, and those of the second stage were the same as those for the first one. The binding isotherms have been well interpreted by the stepwise binding model, which takes account of the free energy decrease due to interactions between bound ligands and of its reduction as the binding step proceeds, and binding constants have been evaluated. On the basis of the binding constants and the free energy changes of binding, the detailed binding mechanism is discussed.
  • Nobuaki Kanamaru
    1998 Volume 71 Issue 10 Pages 2299-2308
    Published: 1998
    Released: June 05, 2006
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    The “Channel 3” phenomena in benzene were investigated concerning a model scheme as an extension of that applied for a typical intermediate case molecule, pyrazine. Using a multiple doorway-states formalism, the difficulties in interpreting such as insufficient density of states for the intermediate dark levels were eliminated based on a preisomerization diagram involving a benzene isomer, most probably benzvalene. By a detailed examination of information about the title subject in the literature concerning both experiments and theory, several questions were raised and answered while making proposals for further study.
  • Shinsaku Fujita
    1998 Volume 71 Issue 10 Pages 2309-2321
    Published: 1998
    Released: June 05, 2006
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    Q-Conjugacy character tables are proposed for finite groups and applied to combinatorial enumeration. Thus, the maturity of an irreducible representation is related to the maturity of a finite group by means of the relationship between the inherent automorphism of the group and its inner portion. As a result, a character table is transformed into a more concise form called a Q-conjugacy character table. Matured characters are defined as dominant-class functions on the basis of such a Q-conjugacy character table. Thereby, a matured character is represented by a linear combination of Q-conjugacy characters. By starting from Q-conjugacy character tables, characteristic monomial tables for finite groups are obtained. They are applied to combinatorial enumeration of isomers.
  • Wei Hua Tan, Takahiro Ishikura, Aya Maruta, Tatsuyuki Yamamoto, Yoshih ...
    1998 Volume 71 Issue 10 Pages 2323-2329
    Published: 1998
    Released: June 05, 2006
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    Complexation of γ-cyclodextrin (γ-CD) with the 2,6-naphthalenedicarboxylate ion (2,6-NDC) in alkaline D2O was greatly enhanced by the addition of 2,6-bis(1-pyridiniomethyl)naphthalene dibromide (2,6-PMN) as a space-regulator. Formation of a ternary 1 : 1 : 1 complex between γ-CD, 2,6-NDC, and 2,6-PMN was confirmed by means of 1H NMR spectroscopy, together with the measurements of induced circular dichroism spectra and UV absorption spectra. Changes in chemical shifts (δ) of the γ-CD protons in the presence of an excess amount of 2,6-PMN with the addition of NDC regioisomers were analyzed by a curve-fitting procedure to give binding constants (K6) for complexation of NDC’s with a γ-CD–2,6-PMN binary complex. The K6 values increased in the order of 1,5-NDC < 1,4-NDC < 1,8-NDC < 1,3-NDC < 1,6-NDC < 2,3-NDC < 2,7-NDC < 2,6-NDC, indicating that a binary complex of γ-CD with 2,6-PMN is able to recognize the molecular structures of NDC’s. The open space between the γ-CD cavity and 2,6-PMN will be favorable for the accommodation of a slender molecule such as 2,6-NDC, but unfavorable for the accommodation of a bulky molecule such as 1,5-NDC.
  • Tetsuya Nanba, Atsushi Uemura, Akifumi Ueno, Masaaki Haneda, Hideaki H ...
    1998 Volume 71 Issue 10 Pages 2331-2337
    Published: 1998
    Released: June 05, 2006
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    Alumina-supported cobalt oxide catalysts were prepared by three different methods: The impregnation and sol/gel methods using either an acid or a base as a precipitant. The catalysts prepared by sol/gel methods, followed by calcination at 773 K, exhibited a significant activity for the selective catalytic reduction (SCR) of NO with propene as a reductant. The catalyst prepared by impregnation showed poor activity when it was calcined at 773 K, but exhibited enhanced activity when calcined at 1073 K. This is attributed to tiny CoAl2O4 crystallites formed during calcination of the catalyst at 1073 K. However, in sol/gel catalysts, finely-divided CoAl2O4 crystallites were formed during calcination, even at 773 K, because of the high dispersion of Co ions in the alumina support. Thus, the active species of alumina-supported cobalt oxide catalysts for SCR of NO with propene were concluded to be tiny CoAl2O4 crystallites dispersed on alumina.
  • Ting-Bin Wen, Bei-Sheng Kang, Cheng-Yong Su, Da-Xu Wu, Li-Ge Wang, Sen ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2339-2343
    Published: 1998
    Released: June 05, 2006
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    The reaction of Cp2TiCl2 with o-mercaptophenolate in the presence of a base (Et3N or NaOMe) afforded the complex (BnMe3N)2[Ti(o-SC6H4O)3] or (Et4N)2[Ti2(o-SC6H4O)4(OMe)2]·2H2O under slightly varied conditions. Single-crystal X-ray diffraction studies showed that the Ti(IV) geometry in both complexes is a severely distorted octahedron with average trans-angles of 162.2° and 159.1(2)°, respectively. Crystallographic data for (BnMe3N)2[Ti(o-SC6H4O)3]: a = 9.884(3), b = 16.501(7), c = 23.028(7) Å; β = 99.89(3)°, V = 3700.2(22) Å3, Z = 4, final R = 0.050 for 3134 observed reflections; for (Et4N)2[Ti2(o-SC6H4O)4(OMe)2]·2H2O: a = 8.953(4), b = 10.148(3), c = 14.527(3) Å; α = 73.16(2)°, β = 73.00(3)°, γ = 83.56(4)°, V = 1207.4(9) Å3, Z = 1, final R = 0.082 for 2233 observed reflections. The isolation of (BnMe3N)2[Ti(o-SC6H4O)3] provides strong evidence for the synthon character of [Ti(mp)3]2−, which was previously predicted to be present in the complex (Et4N)2[Ti(mp)3Na(MeOH)2]2. Both electronic and 1H NMR spectra showed a similar rigidity of the mp chelate rings to Ti(IV) in the complexes.
  • Masaru Kimura, Yuko Shiga, Keiichi Tsukahara
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2345-2350
    Published: 1998
    Released: June 05, 2006
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    The vanadium(V) ion, which is described as VV herein, could hardly oxidize the iodide ion to iodine at pH ≥ 2.8; however, the oxidation reaction occurred catalytically upon adding traces of copper(II) ion. When a copper(II) solution of 10−8—10−5 M (M = mol dm−3) was mixed with an iodide solution, after a rapid formation of iodine, the iodine concentration remained constant. After such iodine formation had occurred, if a VV solution was added into the reacting mixture, the iodine began to form again in accordance with a rate law of 2(d[I2]/dt) = −d[VV]/dt = k[CuI][VV], in which [CuI] is a steady-states’ concentration in a chain cycle CuI+/CuI. The reaction rate was independent of the time to add the VV ion, and the formation of iodine I2 (or triiodide ion I3) stopped at the time when all of the VV was consumed, indicating the stoichiometry to be 2I + 2VV → I2 + 2VIV. The initial rate (Vi) after VV addition was proportional to the concentrations of not only the added VV over the range 10−6—10−5 M, but also the added copper(II) ion. Although a self-inhibiting effect did not appear over the pH range 2.8—3.6, it occurred at pH > 3.6. It was found that such a retarding effect was caused by the vanadium(IV) ion (denoted as VIV herein), which was the reduced product of VV; the VIV inhibiting effect was extremely dependent on the pH in the reacting solution. The mechanisms for the retardation reaction as well as iodine formation are discussed in terms of accounting for the obtained results.
  • Takeo Akiyama, Masaki Amino, Tsutomu Saitou, Koutoku Utsunomiya, Ken-i ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2351-2358
    Published: 1998
    Released: June 05, 2006
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    The X-ray structures and electrochemical properties of the dinuclear cobaltadithiolene complexes, μ-(1,4-disubstituted 1,3-butadiene-1,2,3,4-tetrathiolato)-bis[(η5-cyclopentadienyl)cobalt(III)], have been investigated. In the diphenyl derivative, two benzene rings in the same molecule are located face to face with the distance of 3.5 Å, while in the dimethyl derivative, two methyl groups are in remote positions. However, in the electrically neutral dinuclear complexes, there is no evidence for the intramolecular interaction between two aryl groups in solutions. Electrochemical and spectrochemical investigations revealed that in electrically neutral state, the interaction between two cobaltadithiolene moieties is small, while in monoanioic state it becomes greater. The Hammett’s plot for ΔEr1/2Er1/2 = Er1/2(red.1) − Er1/2(red.2)) shows that the electron-attracting substituents can stabilize the mixed-valence state, [Co(II)–Co(III)]. The smaller ΔEr1/2 values for the complexes having aryl substituents are due to the smaller interactions between the anioic and neutral moieties, because of the steric hindrance of aryl groups which inhibit the conjugation of the two cobaltadithiolene rings.
  • Hajime Katano, Mitsugi Senda
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2359-2363
    Published: 1998
    Released: June 05, 2006
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    The behavior of potential sweep voltammograms for the ion-transfer across the liquid/liquid interface with preceding chemical reactions is discussed. The theoretical results are expressed in the form of the working curves for the peak current, peak potential, and half-peak potential as a function of the kinetic-current parameter, which contains the rate and equilibrium constants of the preceding chemical reaction and the rate of the potential sweep. The working curves are applied to analyze the voltammograms for the transfer of Pb2+ ion to nitrobenzene facilitated by 1,4,7,10,13,16-hexathiacyclooctadecane present in nitrobenzene from aqueous medium containing citrate3− ion. The dissociation and association rate constants and the formation constant of Pb2+–citrate3− complex in W-phase are 4.5 × 104 s−1 and 8.0 × 1010 M−1 s−1and 106.3 M, respectively.
  • Reki Sakamoto, Masaaki Ohba, Nobuo Fukita, Kazuhiro Takahashi, Hisashi ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2365-2373
    Published: 1998
    Released: June 05, 2006
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    5-Carboxysalicylaldehyde (H2casal) formed two mixed-ligand complexes, [Cu(Hcasal)(bpy)]ClO4 (1) and [Cu(casal)(bpy)]·2H2O (2) (bpy = 2,2′-bipyridine) and the Schiff bases H2L1 and H2L2 derived by condensing H2casal with N,N-dimethylethylenediamine and bis(3-aminopropyl)amine, respectively, formed [Cu(L1)]·0.25H2O (3) and [Cu(L2)]·H2O (4), respectively. X-Ray crystallographic studies were done for 1, [Cu(casal)(bpy)(MeOH)] (2′), [Cu(L1)]·4H2O (3′) and 4. 1: Monoclinic, space group C2/c, a = 18.457(5), b = 19.215(5), c = 12.237(3) Å, α = 90, β = 121.76(2), γ = 90°, V = 3690(1) Å3, and Z = 8. It has a dimeric structure with a perchlorato bridge between two [Cu(Hcasal)(bpy)]+ moieties. In the bulk the dimeric units are assembled by interligand noncovalent interactions providing a pseudo 2-D sheet. 2′: Monoclinic, space group P21/m, a = 9.791(4), b = 6.850(4), c = 25.56(1) Å, α = 90, β = 98.99(3), γ = 90°, V = 1692(1) Å3, and Z = 4. The casal2− combines one copper at the mixed-ligand site and the carboxylato group unidentately coordinates to the adjacent molecule, providing a 1-D zipper-like chain. The 1-D chains are further assembled through the interchain bpy/bpy stacking to form a pseudo 2-D network extended on the bc plane. 3′: Tetragonal, space group I41/a, a = b = 16.006(3), c = 27.745(7) Å, α = β = γ = 90°, V = 7108(2) Å3, and Z = 16. It has a 1-D helical structure extended by Cu–NNO(spacer)OO–Cu linkages along c axis (Fig. 6): The nearest Cu–Cu separation in the chain is 9.60 Å. The four water molecules exist in the helical column but are readily removed in the air. 4: Monoclinic, space group P21/c, a = 9.149(6), b = 17.566(6), c = 11.004(6)Å, α = 90, β = 110.03(4), γ = 90°, V = 1661(1) Å3, and Z = 4. It has a 1-D zigzag chain structure extended by Cu–NNNO(spacer)O–Cu linkages. Further, the 1-D chains align through noncovalent interchain interaction to provide a pseudo 2-D sheet. The interplay of the two dissimilar metal-binding sites of H2casal and its Schiff bases and the intermolecular noncovalent interaction contributing to the network and bulk structures of the complexes are discussed.
  • Yanan Xiao, Shinjiro Hayakawa, Yohichi Gohshi, Masaharu Oshima, Hiroki ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2375-2380
    Published: 1998
    Released: June 05, 2006
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    We performed an in-advance simulation and experiments involving resonant X-ray powder diffraction with the incident X-ray energy being near to the absorption edge of a particular element in order to distinguish two chemical states of that element based on the principle of spectro-diffractometry. According to the simulation, we found reflections that are relatively sensitive to the exchange of the two anomalous scattering factors (f′) of the specified element at two crystallographic sites. The simulation and experiment results demonstrated that it is possible to obtain f′ curves for the two chemical states by measuring only a few peaks that are sensitive to f′ without greatly increasing the refinement errors, and that the way of selecting the peaks greatly influence the results. In other words, in-advance simulations are very important in this method. This method may make it possible to obtain nearly the same result in one-tenth machine time, and, moreover, to obtain site-selective XANES for powder samples using limited machine time.
  • Jacir Dal Magro, Rosendo Augusto Yunes
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2381-2385
    Published: 1998
    Released: June 05, 2006
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    The reaction of nitrosobenzene with N-methylhydroxylamine was studied. The pH-rate profile exhibits a negative break at between pH 0.5 and 3.0, which is considered to be caused by a change in the rate-determining step of the reaction from an attack of the amine on nitrosobenzene at low pH, to the dehydration of an addition intermediate previously formed between the reagents at higher pH. This behavior is different from that of the reaction between N-phenylhydroxylamine and nitrosobenzene where, over the entire pH range, the only rate-determining step is dehydration of the addition intermediate. This fact confirms the special behavior of phenylhydroxylamine as a nucleophile, as was observed in its reactions with aromatic aldehydes.
  • Ayman Wahba Erian, Fathi Ali Abu-Shanab
    1998 Volume 71 Issue 10 Pages 2387-2391
    Published: 1998
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    The reaction of azine-thiones with ethyl chlorofluoroacetate afforded 2-fluorothienoazines. The latter underwent self-condensation and gave multi-fused heterocyclic compounds. A wide range of unique heterocycles could be obtained on treatment of 2-fluorothienoazines with nitrogen nucleophilic reagents. The reactivity of the pyrimidine-thiones towards a variety of electrophilic reagents was studied. Chemical and spectroscopic evidence of the newly synthesized compounds are described.
  • Yoshihiro Ohba, Kazuaki Ito, Hiroyuki Maeda, Hiroaki Ebara, Shin Takak ...
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2393-2402
    Published: 1998
    Released: June 05, 2006
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    Several ligands for a new type of Lewis acid, which incorporates two linked phenols, were synthesized and the reaction of these ligands with trimethylaluminum quantitatively gave Lewis acids. These Lewis acids were found to be an efficient promoter for the rearrangement of epoxides to carbonyl compounds as well as a useful protector of acetophenone against hydride-reduction. The VT-NMR spectrum and NOESY spectrum of a 1 : 1 complex of Lewis acid 2a (methyl[2,2′-(m-xylene-α,α′-diyl)bis(4,6-di-t-butylphenoxido)aluminum and acetophenone provided data on the structure of a complex of acetophenone and 2a.
  • Shoji Hara, Hisashi Shudoh, Shigeyuki Ishimura, Akira Suzuki
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2403-2408
    Published: 1998
    Released: June 05, 2006
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    The effect of substituents on the double bond of α,β-unsaturated ketones for the 1,4-addition reaction rate of alkenylboronic acids induced by cyanuric fluoride was studied in detail. When the steric hindrance around the β-carbon of the unsaturated ketones increased, the 1,4-addition reaction rate significantly decreased. An alkyl substituent on the α-carbon was also found to significantly affect the 1,4-addition reaction. From these results, unsymmetric α,β,α′,β′-unsaturated ketones (10af) were designed for the regioselective 1,4-addition reaction with alkenylboronic acids (4aj). Since they have substituents to disturb the 1,4-addition reaction on only one double bond, the alkenylboronic acids reacted with them from only one side to selectively provide γ,δ,α′,β′-unsaturated ketones (11aq). Further transformations of the resulting γ,δ,α′,β′-unsaturated ketones were also performed.
  • Kazunori Hirabayashi, Eisuke Takahisa, Yasushi Nishihara, Atsunori Mor ...
    1998 Volume 71 Issue 10 Pages 2409-2417
    Published: 1998
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    Alkenylsilanols are prepared by the reaction of hexamethyltrisiloxane (D3) with alkenyllithiums or alternatively by the reaction of cyclic siloxanes substituted by an alkenyl group with organolithiums and transformed to the corresponding cyclopropylsilanols using diiodomethane and diethylzinc. Lithium alkenylsilanolates, primary products of the preparation, also undergo cyclopropanation. As in the case of allylic alcohols, the silanol functionality is found to enhance the rate of cyclopropanation compared with that of alkenyltrialkylsilane or alkoxydialkylsilane. The obtained cyclopropylsilanols are further converted into the corresponding cyclopropanols by the Tamao oxidation.
  • Kenji Arakawa, Tadashi Eguchi, Katsumi Kakinuma
    1998 Volume 71 Issue 10 Pages 2419-2426
    Published: 1998
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    Described in this paper is a practical synthesis of the specifically deuterated 36-membered macrocyclic diether lipid 4 and its acyclic deuterated counterpart 5, both of which are essential to the detailed biophysical studies of the conformational order of phospholipids in vesicles. The synthesis of 4 was principally composed of the preparation of deuterated diether 15, subsequent macrocyclization of the crucial dialdehyde 21 by McMurry coupling, and final transformation into the phosphocholine derivative. The acyclic deuterated counterpart 5 was also synthesized from the common intermediary tosylate 16.
  • Masaaki Mishima, Hiroshi Yamataka
    1998 Volume 71 Issue 10 Pages 2427-2432
    Published: 1998
    Released: June 05, 2006
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    Ab initio molecular-orbital calculations were carried out for two carbocation-generating reactions, the SN1 reaction of protonated 1-phenylethyl alcohol (H2O leaving group) and the acid-catalyzed hydration of styrene. Separated reactants, reactant complexes, transition states (TSs), product complex, and separated products were optimized at MP2/6-31G* and the vibrational frequencies were analyzed. The SN1 TS lies halfway between the reactant and the product with respect to the bond lengths, charge distribution, and secondary deuterium isotope effects. The degree of the π-orbital overlap between the benzylic carbon and the phenyl ring is almost the same in the SN1 TS and the 1-phenylethyl cation. The proton-transfer TS of the hydration, on the other hand, reaches earlier, and the π-orbital overlap in the TS is less effective. These differences are responsible for the difference in the experimental substituent effect reported in the literature for the two reactions.
  • Katsuhide Ohi, Kyoko Shima, Kozue Hamada, Yoshio Saito, Naoki Yamada, ...
    1998 Volume 71 Issue 10 Pages 2433-2440
    Published: 1998
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    The C1—C13 fragment of amphidinolide B (1) was synthesized from D-erythrose (3). The Evans alkylation reaction protocol allowed the introduction of the stereogenic center at the C11 position, which was unambiguously confirmed by a single X-ray crystallographic analysis.
  • Hideo Nagashima, Akihiro Suzuki, Mitsuharu Nobata, Katsuyuki Aoki, Ken ...
    1998 Volume 71 Issue 10 Pages 2441-2448
    Published: 1998
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    Hydrogenation of di-, tri-, and tetranuclear ruthenium carbonyl complexes bearing guaiazulene or 4,6,8-trimethylazulene as the bridging ligand to bind the multimetallic framework was studied: [μ2 : η-guaiazulene)Ru2(CO)5 (1a)], [μ2 : η-4,6,8-trimethylazulene)Ru2(CO)5 (1b)], [(μ3 : η-guaiazulene)Ru3(CO)7 (2a)], [(μ3 : η-4,6,8-trimethylazulene)Ru3(CO)7 (2b)], [(μ3 : η-guaiazulene)Ru4(CO)9 (3a)], and [(μ3 : η-4,6,8-trimethylazulene)Ru4(CO)9 (3b)]. Reactions of these di-, tri-, and tetraruthenium complexes with dihydrogen (PH2 = 5—10 atm) at 100 °C resulted in cluster fragmentation and addition of five hydrogen atoms to the azulene ligands to form mononuclear ruthenium carbonyl hydride compounds, [(η5-pentahydroguaiazulenyl)RuH(CO)2 (4a)] or [(η5-pentahydrotrimethylazulenyl)RuH(CO)2 (4b)]. Despite potential formation of several stereoisomers dependent on the addition modes of hydrogen atoms, only one isomer of 4a or 4b was obtained in the hydrogenation. The crystal structure of a derivative of 4a revealed that the addition of hydrogen atoms occurred from the face of the azulene ligand originally bonded with the ruthenium species. Hydrogenation of the di-, tri-, and tetranuclear ruthenium complexes below 100 °C revealed that only the triruthenium compounds reacted with H2 at 50 °C via triruthenium dihydride intermediates: [(μ2: η-tetrahydroguaiazulene)Ru3H2(CO)7 (6a)] or [(μ2: η-tetrahydrotrimethylazulene)Ru3H2(CO)7 (6b)]; this indicates that there exists a reaction pathway to achieve facile activation of dihydrogen by the triruthenium clusters.
  • Masafumi Unno, Hiroyuki Masuda, Hideyuki Matsumoto
    Type: Accounts
    Subject area: AI
    1998 Volume 71 Issue 10 Pages 2449-2458
    Published: 1998
    Released: June 05, 2006
    JOURNALS RESTRICTED ACCESS
    Reaction of dichlorophenylthexylsilane (thexyl = 1,1,2-trimethylpropyl) with lithium naphthalenide in tetrahydrofuran at −65 °C gave cis,cis- and cis,trans-1,2,3-triphenyl-1,2,3-trithexylcyclotrisilane 1 (cis,cis-1 and cis,trans-1) in yields of 19 and 52%, respectively. The structures of both isomers were determined by X-ray crystallography. The ring-opening reaction of each isomer with bromine leads to the formation of 1,3-dibromo-1,2,3-triphenyl-1,2,3-trithexyltrisilane (2); cis,cis-1 gave only (1R,3R)/(1S,3S)-1,3-dibromo-1,2,3-triphenyl-1,2,3-trithexyltrisilane ((1R,3R)/(1S,3S)-2) (87% yield). While cis,trans-1 formed (1R,2s,3S)- and (1R,2r,3S)-1,3-dibromo-1,2,3-triphenyl-1,2,3-trithexyltrisilane ((1R,2s,3S)-2 and (1R,2r,3S)-2, in 13 and 31% yields) as well as (1R,3R)/(1S/3S)-2 (44% yield). The structures of (1R,3R)/(1S,3S)-2 and (1R,2r,3S)-2 were confirmed by X-ray crystallography. From the stereochemical results observed in the ring-opening reactions, it is concluded that the cleavage of the Si–Si bonds occurs with retention–inversion of the configuration of the silicon atoms. In the chlorination, cis,cis-1 gave (1R,3R)/(1S,3S)-1,3-dichloro-1,2,3-triphenyl-1,2,3-trithexyltrisilane ((1R,3R)/(1S,3S)-3, 40% yield) and (1R,2r,3S)-1,3-dichloro-1,2,3-triphenyl-1,2,3-trithexyltrisilane ((1R,2r,3S)-3, 30% yield); cis,trans-1 gave (1R,3R)/(1S,3S)-3 (33% yield), (1R,2r,3S)-3 (14% yield), and (1R,2s,3S)-1,3-dichloro-1,2,3-triphenyl-1,2,3-trithexyltrisilane in 40% yield. The structure of (1R,2r,3S)-3 was confirmed by X-ray crystallography. The result indicates that stereoselectivity was lower in the ring-opening by chlorine than in that by bromine.
  • Yoshinobu Izumi, Shunichi Kawanishi, Noriaki Takagi, Shigeo Honda, Tad ...
    1998 Volume 71 Issue 10 Pages 2459-2463
    Published: 1998
    Released: June 05, 2006
    JOURNALS RESTRICTED ACCESS
    Vinylidene chloride–vinyl chloride copolymer (Saran® copolymer) film was irradiated with ArF and KrF excimer laser light in a vacuum at ambient temperature. The irradiation of ArF and KrF excimer laser light mainly caused the formation of diene and triene structures, respectively. From the dependence on the laser intensity it was concluded that diene and triene were formed via single-photon and multi-photon processes, respectively. The wavelength dependence was explained by photochemical and photothermal effects for the ArF and KrF lasers, respectively.
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