Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 73 , Issue 2
Showing 1-29 articles out of 29 articles from the selected issue
  • Haruo Shizuka, Minoru Yamaji
    2000 Volume 73 Issue 2 Pages 267-280
    Published: 2000
    Released: October 31, 2001
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    Photochemical and photophysical aspects of (1) triplet energy transfer (TET) from triplet benzophenone (BP) to naphthalene derivatives (NpD) and (2) formation and decay processes of triplet exciplexes between 3NpD* and BP have been studied by 355-nm laser photolysis techniques in the liquid phase. As an initial event, TET occurs from 3BP* to NpD competing with H-atom transfer (HT), electron transfer (ET), and induced quenching (IQ) on the nanosecond time scale. The TET rate constant increases with an increase of solvent polarity while that of HT decreases, indicating that the 3(n, π*) state of BP is slightly mixed with 1(π, π*) in polar media. After formation of 3NpD* by TET from 3BP*, chemical reactions via triplet exciplexes between 3NpD* and BP having loose sandwich-like structures with weak charge transfer character take place in the microsecond time scale, depending on the substituent groups of NpD. (1) HT from triplet 2-naphthylammoniun ion and triplet naphthol to BP occurs efficiently to yield the 2-naphthylamine cation radical and naphthoxy radical plus the benzophenone ketyl radical, respectively. The more protic H-atom in NpD is the more reactive in HT. (2) The proton-induced ET from triplet methoxynaphthalene to BP takes place effectively via the protonated triplet exciplex to give the methoxynaphthalene cation and benzophenone ketyl radical. (3) Hydrogen bonding-induced ET from triplet N, N-dialkyl-1-naphthylamine to BP occurs to yield the N-dialkyl-1-naphthylamine cation radical and benzophenone anion radical in the presence of protic solvents.
  • Shireen Basheer Sulthana, Sodankoor Garadi Thirumaleshwar Bhat, Animes ...
    2000 Volume 73 Issue 2 Pages 281-287
    Published: 2000
    Released: October 31, 2001
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    The solution properties of sodium dodecylbenzenesulfonate (SDBS) in an aqueous medium in the presence of additives, like polyethylene glycol 400 (PEG 400), sucrose, and urea, have been investigated. The critical micelle concentration (cmc) was determined by both surface-tension and conductivity methods. The cmc values were found to increase along with an increase in the temperature in both the presence and absence of additives at all of the concentrations studied. The interfacial parameters, such as the maximum surface excess (Γmax) and minimum area per molecule (Amin), were computed from surface-tension data. The thermodynamic parameters of micellization and adsorption at air/water interfaces were also evaluated. Other properties, such as the micellar aggregation number (Nagg), viscosity, foaming, wetting, and detergency by dye solubilization, were also studied.
  • Kazuhiko Honda
    2000 Volume 73 Issue 2 Pages 289-295
    Published: 2000
    Released: October 31, 2001
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    Hydrogen-bond-enhanced interactions were generated for ammonia pairs by ab initio calculations using tempered basis sets. The potential function obtained by the generation of interaction energies was applied to a Monte Carlo simulation for the liquid state of ammonia. The simulated bulk properties were considered compared with a previous ab initio STO-3G based simulation. The thermodynamic properties were obtained in the simulation and compared with those of a liquid water system to which the same manner of enhancement for the hydrogen bond was applied. The qualitative difference between the two liquids was reproduced.
  • Tadayoshi Sakata
    2000 Volume 73 Issue 2 Pages 297-305
    Published: 2000
    Released: October 31, 2001
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    The quantum mechanical theory of electrode reactions was applied to a hydrogen evolution reaction. The dependence of the activation energy of the hydrogen exchange current densities on the kind of electrode metal was explained well by this theory. The magnitude of the hydrogen exchange current densities and hydrogen overvoltages at various metal electrodes were evaluated theoretically. The calculated results and the dependency on the kind of metal were found to agree well quantitatively with the experimental values.
  • Keizo Horiuchi, Himiko Takayama, Shin'ichi Ishimaru, Ryuichi Ikeda
    2000 Volume 73 Issue 2 Pages 307-314
    Published: 2000
    Released: October 31, 2001
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    1H NMR spin-lattice relaxation times T1 and T1ρ as well as the electrical conductivity were measured as a function of temperature in (n-C5H11NH3)2ZnCl4 and (n-C12H25NH3)2ZnCl4. The highest-temperature solid phase in both compounds was found to be the rotator phase, where rod-like cations perform uniaxial reorientations about the molecular long axes accompanied by conformational disordering and translational self-diffusion of the cations within the layer perpendicular to c-axis. In the rotator phase, the cations are considered to have a non-intercalated double layer structure. These rotator phases were shown to be quite analogous to those reported in n-alkylammonium chlorides. (n-C5H11NH3)2ZnCl4 undergoes four structural phase transitions, while (n-C12H25NH3)2ZnCl4 exhibits a single transition above ca. 120 K. All of these transitions were shown to be of order-disorder type.
  • Hideaki Takahashi, Kazuhiro Okuda, Tomoshige Nitta
    2000 Volume 73 Issue 2 Pages 315-319
    Published: 2000
    Released: October 31, 2001
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    The intermolecular interaction between a CO2 molecule and an MgO cluster has been investigated by ab initio molecular orbital method in order to test a selection rule for chemical modifications of surfaces. Favorable adsorption geometry has been determined by partial geometry optimizations initiated from three possible formations of the molecular complex. A CO3-form where the carbon atom is coordinated to an O atom of the MgO cluster is found to be most stable. The Kitaura-Morokuma energy decomposition analysis has been carried out to investigate the nature of the intermolecular interaction between a CO2 molecule and an MgO cluster. It is found that charge transfer energy from the MgO cluster to CO2 is the dominant component in the total stabilization energy. Two Mg atoms are replaced by two Ca atoms to enhance the electron flow from an MgO cluster to a CO2 molecule, which resulted in the increase in the adsorption energy. The effect of the chemical modification is examined by the energy decomposition analysis. We confirm that the increase of the cohesive energy is a consequence of the increase in charge transfer interaction from the cluster to the CO2 molecule. The mechanism of the charge transfer is also studied by the molecular orbital analysis.
  • John F. Ogilvie, Hiromichi Uehara, Koui Horiai
    2000 Volume 73 Issue 2 Pages 321-327
    Published: 2000
    Released: October 31, 2001
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    With laser diodes we measured spectra of RbCl vapor near 1000 K in absorption in a region 43800—46400 m-1 and assigned vibration-rotational transitions, 226 of 85Rb35Cl up to ν = 9 and J = 160, 158 transitions of 85Rb37Cl and 125 of 87Rb35Cl, all with Δν = 2. We made a global fit of these 509 new data plus 28 published pure rotational transitions. Of eight evaluated parameters, six are adjusted, pertaining to a function for potential energy, and two are constrained, pertaining to nonadiabatic rotational effects; these parameters suffice to reproduce these data generally within uncertainties of their measurement. Comparison is made with corresponding spectral parameters of HCl, LiCl, NaCl and KCl.
  • Shinsaku Fujita
    2000 Volume 73 Issue 2 Pages 329-339
    Published: 2000
    Released: October 31, 2001
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    Generalized partial cycle indices have been proposed as a generalization of partial cycle indices (PCIs) in order to enumerate isomers with a given set of subsymmetries. To evaluate the coefficient of each term appearing in such a generalized PCI, the natures of a mark table and of its inverse have been examined after the proposal of (modified) bisected mark tables and their inverses as well as of (modified) bisected tables of unit subduced cycle indices with chirality fittingness (USCI-CFs). The inverse of a (modified) bisected mark table and the (modified) bisected USCI-CF table have been applied to the enumeration of chiral isomers and achiral isomers.
  • Vedachalam Sundaramurthy, Nachiappan Lingappan
    2000 Volume 73 Issue 2 Pages 341-346
    Published: 2000
    Released: October 31, 2001
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    Pentasil zeolite, B-ZSM-5 and Al-ZSM-5, have been synthesized hydrothermally using orthoboric acid and sodium aluminate, respectively, with ethyl silicate-40 so as to obtain a gel mix with SiO2/M2O3 = 22 (where M = B or Al) employing a tetrabutylphosphonium bromide (TBPBr) template at temperatures of 423, 448, and 473 K. The crystallization kinetics followed by XRD, FTIR, and SEM studies clearly demonstrate the influence of the size of the hetero atoms on the rate of nucleation and crystallization. The values of the apparent activation energies for nucleation and crystal growth indicate that both nucleation and crystal growth are faster for the Al-ZSM-5 system than for the B-ZSM-5 system. Avrami-Erofeev parameters for both systems have been evaluated. Correlations were found between the kinetics of crystallization and the characteristics of the formed crystal. SEM pictures show similar, but larger sized, crystals for the Al-ZSM-5 system than those of the B-ZSM-5 system. XRD, FTIR, and chemical analysis have revealed that the mechanism operating during crystallization is the same, and that hetero atoms become incorporated with the framework during the nucleation step, itself, with boron at a slower rate.
  • Masashi Hojo, Tadaharu Ueda, Kazushi Kawamura, Masanori Yamasaki
    2000 Volume 73 Issue 2 Pages 347-355
    Published: 2000
    Released: October 31, 2001
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    With the addition of alkali metal (M+) and alkaline earth metal (M2+) perchlorates, the cause of the color changes of several sulfonephthaleins of various pKa values, i.e., Thymol Blue, Phenol Red, Bromothymol Blue, and Bromocresol Green, in acetonitrile solutions were examined by means of spectrophotometry and 1H NMR. Upon the addition of ≥ 0.1 mol dm-3 LiClO4 to 1.0 × 10-4 mol dm-3 Phenol Red, the γ-sultone ring of the sulfonephthalein was cleaved to give absorption bands at around 410 and 500 nm. The band at 500 nm was assigned to the acid form, and that around 410 nm to a quinonoid structure (the intermediate form) which would be formed by deprotonation from the acid form. The effects of NaClO4 were much smaller than those of LiClO4. Magnesium and barium perchlorates caused larger effects than LiClO4; however, a nonmetallic salt, Et4NClO4, caused almost no effects. In addition, a purple-red colored species (λmax = 563 nm), a basic form, was also produced from Phenol Red by the addition of ≥ 0.2 mol dm-3 Mg(ClO4)2. Interestingly, the metal ions assisted not only the acid effects of CH3SO3H, but also the base effects of Et3N or 1,1,3,3-tetramethylguanidine on Phenol Red or Bromothymol Blue in acetonitrile. 1H NMR spectra of the sulfonephthaleins confirmed the opening of the γ-sultone rings in the presence of the metal salts. The ring cleavage upon the addition of the metal ions was considered from the standpoint of not ``medium effects'', but a direct chemical interaction between the metal ions and the sulfonate ion (function) in the sulfonephthaleins.
  • Nimma Rajaiah Sangeetha, Samudranil Pal
    2000 Volume 73 Issue 2 Pages 357-363
    Published: 2000
    Released: October 31, 2001
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    Dark-brown complexes of {OV(μ-O)VO}4+ with the general formula [(VOL)2O] were isolated from reactions of bis(acetylacetonato)oxovanadium(IV) and aroylhydrazones of salicylaldehyde or of 5-methoxysalicylaldehyde (H2L, two H stand for the dissociable protons at the phenol and the amide functionalities) in acetonitrile. The infrared spectra of these complexes are consistent with the dianionic form of the ligands. The electronic spectral profiles are very similar and display strong absorptions in the range 425—263 nm due to ligand-to-metal charge transfer and intraligand transitions. The proton NMR spectra suggest that in solution the two ligands in each complex are magnetically equivalent. The complexes are redox active and display a reduction response in the potential range -0.28—0.47 V (vs. Ag/AgCl). The molecular structures of the complexes were determined by X-ray crystallography. The deprotonated dianionic planar ligands coordinate the metal ions through the phenolate-O, the imine-N, and the amide-O atoms forming a six-membered and a five-membered chelate ring. The metal ions in each complex are essentially in a square-pyramidal O4N coordination sphere. The O, N, O-donor ligand and the bridging oxygen atom constitute the square plane and the oxo group occupies the apical position. The metal center is displaced from the basal plane towards the apical oxo group by 0.44—0.57 Å. The V-O-V bridge angles in the complexes are very similar and within the range 112.86(13) to 115.89(12)°.
  • Takashi Fujii, Kazuo Miyamura
    2000 Volume 73 Issue 2 Pages 365-368
    Published: 2000
    Released: October 31, 2001
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    A monolayer of bis(5-butylsalicylidene)ethylenediaminatonickel(II), prepared on highly oriented pyrolytic graphite by the Langmuir-Blodgett method, was observed by scanning tunnelling microscopy. The image revealed that one of the monolayers was comprised dimers of complexes, similar to that observed in the crystalline phase. The π-A isotherms of the analogues of various alkyl chain lengths were measured, and the critical area of the monolayer was found to decrease by 20% when the alkyl chain length decreased from 3 (propyl) to 2 (ethyl). This decrease of the critical area is explained by the presence of CH-π interactions between the π conjugated system of the salen moiety, and α- and γ-methylenes of the alkyl side chain.
  • Gakuse Hoshina, Masanobu Tsuchimoto, Shigeru Ohba
    2000 Volume 73 Issue 2 Pages 369-374
    Published: 2000
    Released: October 31, 2001
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    A dehydrogenation reaction of the red-brown powder of [Ni(3-EtOsal-meso-stien)] (H2(3–EtOsal–meso–stien) = N,N-bis(3-ethoxysalicylidene)-(R,S)(S,R)-1,2-diphenyl-1,2-ethanediamine) did not occur by heating solely in the air up to 210 °C. However, the reaction occurred upon heating together with [VO(salen)] (H2(salen) = N,N-disalicylidene-1,2-ethanediamine) in the air at 190 °C, and a red powder of [Ni(3-EtOsalton)] (H2(3-EtOsalton) = N,N-bis(3-ethoxysalicylidene)-1,2-diphenyl-1,2-ethenediamine) was obtained. The dehydrogenation reaction could also be carried out under Ar at 160 °C by mixing with [VO(salen)]NO3. These facts revealed that the oxidants in solid state dehydrogenation in air are the VV species originating from the VIV=O complex. The crystal structures of [Ni(3-EtOsal-meso-stien)]·CH3CN·H2O, (1); [Ni(3-EtOsal-rac-stien)]·0.5H2O, (2); and [Ni(3-EtOsalton)]·CH3OH·1.33H2O, (3) were determined by X-ray analyses. [Ni(3-EtOsalton)] was prepared in a dioxane solution of [Ni(3-EtOsalstien)] using DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) as an oxidant. The rac complex, [Ni(3-EtOsal-rac-stien)] (H2(3–EtOsal–rac–stien) = N,N-bis(3-ethoxysalicylidene)-(R,R)(S,S)-1,2-diphenyl-1,2-ethanediamine), is less reactive in dehydrogenation than the meso in the solid state as well as in solution. The molecular structures in (1) and (2) indicate that the benzylic H atoms are sterically protected by phenyl groups in the rac complex, but are exposed to the oxidant in the meso complex.
  • Haruo Naruke, Toshihiro Yamase
    2000 Volume 73 Issue 2 Pages 375-382
    Published: 2000
    Released: October 31, 2001
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    Two isostructural anions, [Ln(BW11O39)(W5O18)]12- (Ln = Ce and Eu), were isolated as K+ salts from aqueous solutions containing tungstate, Ln3+, and BO33-, at pH = 7. An X-ray crystallographic analysis showed that the Ln3+ center in the anion is chelated by two kinds of tetradentate polyoxotungstate ligands, [W5O18]6- and α-[BW11O39]9- with a square antiprismatic LnO8 configuration, which are monovacant derivatives of [W6O19]2- and α-[BW12O40]5-, respectively. The anion is of approximate Cs symmetry, and the observable asymmetry of K-O bonding between two different K+ cations and the anion causes the two mirror planes within [(W5O18)Ln]3- and [(BW11O39)Ln]6- moieties to be canted to each other by 5.2° for Ln = Ce and 4.1° for Ln = Eu.
  • Tetsuaki Fujihara, Koji Hoshiba, Yoichi Sasaki, Taira Imamura
    2000 Volume 73 Issue 2 Pages 383-390
    Published: 2000
    Released: October 31, 2001
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    Reversibility in the formation reaction of a series of the oxo(peroxo)porphyrinatomolybdenums, [MoVIO(tmp)(O2)] 1, [MoVIO(tdcpp)(O2)] 2, [MoVIO(ttp)(O2)] 3, [MoVIO(tdmpp)(O2)] 4, and [MoVIO(tpp)(O2)] 5, was studied. In these dioxygen complexes with various porphyrin rings, two complexes, 2 and 4, were newly prepared by the solid-state reactions of corresponding Mo(IV) complexes with O2. All the complexes were characterized by IR, 1H NMR, and UV-vis spectroscopic measurements. In the reaction of O2 with [MoIVO(tdcpp)] 2r, which has bulky substituents with an electron-withdrawal character, the association rate constant was determined to be 1.2 × 10-2 dm3 mol-1 s-1 in toluene at 20 °C. The value of the rate constant is about one thirtieth of that for [MoIVO(tmp)] 1r, which also has bulky substituents. The result indicates that the electronic effects of the porphyrin rings, which reflect on the redox potentials of the central molybdenum ion, are important in determining kinetic and thermodynamic stability of the dioxygen complexes. All the dioxygen complexes undergo deoxygenation upon photoirradiation to give corresponding [MoIVO(por)]. The redioxygenation profiles of [MoIVO(por)] in the dark were also significantly affected by the steric bulkiness of the porphyrin ligands. While the bulky porphyrin complexes of 1 and 2 gave full recovery of the dioxygen complexes in the dark, less bulky porphyrin complexes of 3, 4, and 5 undergo some side reactions to Mo(V) species. The rate and extent of the Mo(V) complex formations increase with decreasing steric bulkiness.
  • Kunihisa Sugimoto, Takayoshi Kuroda-Sowa, Masahiko Maekawa, Megumu Mun ...
    2000 Volume 73 Issue 2 Pages 391-394
    Published: 2000
    Released: October 31, 2001
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    Oxidation of [Pd(mnt)2]2- by H2O2 produces a sulfonyl-containing [Pd(mnt){O2S2C2(CN)2}]2- (12-). Addition of AgClO4 to 12- results in the formation of [AgPd(mnt){O2S2C2(CN)2}]22- (22-). Both compounds crystallize with a bulky cation Bu4N+ to form (Bu4N)21 and (Bu4N)22, which are characterized by single crystal X-ray analyses. 12- retains a planar structure except for the sulfonyl oxygen atoms. The electronic absorption band observed at 387 nm (sh) is assigned to d-d transition. 22- has a double-decker structure consisting of two [Pd(mnt){O2S2C2(CN)2}]2- anions bridged by two Ag(I) ions through Ag-S bonds. Two terminal CN groups in 22- coordinate to the neighboring Ag(I) ions, forming a one-dimensional chain structure. Crystallographic data are as follows. (Bu4N)21: PdS4O2N6C40H72, triclinic, P1-, a = 12.145(2), b = 10.991(3), c = 10.156(2) Å, α = 65.09(2), β = 88.93(2), γ = 84.97(2)°, Z = 1. (Bu4N)22: Ag2Pd2S8O4N10C48H72, monoclinic, P21/c, a = 9.649(2), b = 13.235(2), c = 25.107(2) Å, β = 91.03(1)°, Z = 2.
  • Ananda S. Amarasekara, W. Wimal Pathmasiri
    2000 Volume 73 Issue 2 Pages 395-399
    Published: 2000
    Released: October 31, 2001
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    Maleimides react with 2-furaldehyde phenylhydrazone 1 at the furan ring to give 4-(phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones when equimolar mixtures are refluxed in benzene for shorter reaction times. Excess maleimides and longer reaction times give mixtures of 4-(phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones and 3-(1,3-dihydro-1,3-dioxo-4-isoindolyl)-1,6a-dihydropyrrolo[3,4-c]pyrazolo-4,6(3aH,5H)-diones resulting from [4+2] and [3+2] double-cycloaddition. Reactions of 1 with dimethyl acetylene dicarboxylate give the double-cycloaddition product dimethyl-3[4-hydroxy-2,3-bis(methoxycarbonyl)phenyl]-1-phenylpyrazole-4,5-dicarboxylate. Methyl acrylate and acrylonitrile gives only the [3+2] cycloaddition products, 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carboxylic methyl ester and 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carbonitrile, respectively.
  • Kazunari Yoshizawa, Takehiro Ohta, Masataka Eda, Tokio Yamabe
    2000 Volume 73 Issue 2 Pages 401-407
    Published: 2000
    Released: October 31, 2001
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    A possible two-step mechanism for the hydrocarbon hydroxylation by the oxoferryl active species of cytochrome P450 is discussed. We propose that the catalytic reaction is initiated by the formation of a reactant complex involving a five-coordinate carbon species or a σ-complex, followed by concerted hydrogen and alkyl migrations which lead to the formation of a product complex involving alcohol as a ligand. The porphyrin ring is predicted from molecular mechanics and extended Hückel calculations to be significantly bent in the reactant complex and in the hydroxy intermediate to form an energetically preferred octahedral environment at the iron active center. Such bent structures for the porphyrin ring are consistent with observed cis-coordination geometries for the M(porphyrin)L2 complexes, in which M is a large transition-metal ion and L is a ligand. We suggest that possible inversion at the five-coordinate carbon species in the reactant complex can occur to lead to partial inversion of stereochemistry at a labeled carbon.
  • Toshiyuki Itoh, Hitomi Inoue, Sachie Emoto
    2000 Volume 73 Issue 2 Pages 409-416
    Published: 2000
    Released: October 31, 2001
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    Synthesis of (1S,2R)-1-[(E)-hex-1-en-1-yl]-2-vinylcyclopropane (dictyopterene A), which was isolated from the essential oil of algae of the genus Dictyopteris in Hawaii, has been demonstrated using optically active tributylstannylcyclopropane as a starting chiral synthon.
  • Chiaki Kuroda, Atsushi Ochi, Noritoshi Nakane, Takashi Umeyama, Nobuko ...
    2000 Volume 73 Issue 2 Pages 417-422
    Published: 2000
    Released: October 31, 2001
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    (2S,5S)-5-(3-Formyl-6-iodo-4-methoxybenzyl)-1-t-butoxycarbonyl-2-t-butyl-3-methyl-4-imidazolidinone (11), a chiral intermediate towards NCA PET tracer 6-[18F]fluoro-L-dopa (1), was synthesized from 3-iodoanisole in four steps. 3-Iodoanisole was first bischloromethylated to 2,4-bis(chloromethyl)-5-iodoanisole (14). Regio- and enantio-selective alkylation of 14 with (S)-1-(t-butoxycarbonyl)-2-t-butyl-3-methyl-4-imidazolidinone (12) afforded 33, which was then hydrolyzed and oxidized to the desired intermediate 11.
  • Tomoyuki Hasegawa, Hisashi Yamamoto
    2000 Volume 73 Issue 2 Pages 423-428
    Published: 2000
    Released: October 31, 2001
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    (R)-2-Propyloctanoic acid has been developed as a novel therapeutic agent for Alzheimer's disease. A large-scale synthesis of this candidate was achieved by using Oppolzer's camphorsultam as a chiral auxiliary under improved conditions. It was essential for the successful synthesis of this compound to utilize a new removal method for the chiral source with a combination of tetrabutylammonium hydroxide and hydrogen peroxide. The present process afforded the desired product in high yield with high optical purity.
  • Tohru Nakashima, Ryoji Fujiyama, Hyun-Joong Kim, Mizue Fujio, Yuho Tsu ...
    2000 Volume 73 Issue 2 Pages 429-438
    Published: 2000
    Released: October 31, 2001
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    Solvolysis rates of 3-(aryldimethylsilyl)propyl p-toluenesulfonates were determined in various solvents. The reaction mechanism of this simple γ-silyl system was clarified based on the solvent effect and the substituent effect analyses. The solvent effect on this system clearly showed the nucleophilic assistance of solvent, but failed to correlate linearly with the extended Winstein-Grunwald equation, substantiating that the reaction should not proceed through either the formation of the cation intermediate or the SN2 mechanism. This suggests that the reaction takes place in competition between γ-silyl-assisted (kSi) and solvent-assisted (ks) pathways, and that the competition ratio varies with solvents and with aryl substituents. Product analysis revealed that the former pathway gave only cyclopropane and the latter gave only the substitution products. The overall kt value could be dissected into the partial rate constants kSi and ks for the two pathways by using product ratios. The effects of aryl substituents at the γ-silyl atom on kSi pathway were correlated with unexalted σ° parameter, giving the ρ values of -1.0 in 60E and -1.32 in 97Tw, and reflecting the delocalization of incipient carbocationic charge by participation of the Si-Cγ bond. The substituent effects on the ks pathway were negligibly small; this is in line with the remote reaction center in the concerted SN2 mechanism.
  • Toru Arai, Takashi Imachi, Tamaki Kato, Norikazu Nishino
    2000 Volume 73 Issue 2 Pages 439-445
    Published: 2000
    Released: October 31, 2001
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    Amphiphilic 21-peptides with six and nine L-2-(2,2,2-trifluoroethyl)glycines as the hydrophobic amino acids and lysine and glutamic acid as the hydrophilic amino acids were synthesized. The CD spectra showed that these peptides with L-2-(2,2,2-trifluoroethyl)glycines took a random conformation in H2O. On the contrary, similar amphiphilic 21-peptides with leucine as the hydrophobic amino acids took a helical conformation in H2O. The peptides with L-2-(2,2,2-trifluoroethyl)glycines took a helical conformation in H2O containing a > 20% volume of 2,2,2-trifluoroethanol. These facts suggested the hydrophobic nature of the L-trifluoroethylglycines. The peptide with six L-2-(2,2,2-trifluoroethyl)glycines took a helical structure in methanol, however it slowly changed into the β-structure within 24 h. Interestingly, the peptide with nine L-2-(2,2,2-trifluoroethyl)glycines formed a stable helix under the same conditions. The peptide with nine L-2-(2,2,2-trifluoroethyl)glycines preferred a helical structure, probably because the assembling of the Tfeg side chains was more effective in forming its helix rather than the β-structure.
  • Yutaka Ukaji, Yuuko Shimizu, Yuuichi Kenmoku, Alauddin Ahmed, Katsuhik ...
    2000 Volume 73 Issue 2 Pages 447-452
    Published: 2000
    Released: October 31, 2001
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    The catalytic asymmetric addition of dialkylzinc to a carbon-nitrogen double bond in 3,4-dihydroisoquinoline N-oxides was achieved by utilizing a catalytic amount of 2-magnesium 3-zinc salt of dicyclopentyl (R,R)-tartrate to afford (S)-1-alkyl-2-hydroxy-1,2,3,4-tetrahydroisoquinolines. In order to realize higher enantioselectivity, it was crucial to add the nitrones slowly into dialkylzinc in the presence of a catalytic amount of the 2-magnesium 3-zinc salt of (R,R)-tartrate.
  • Masato Oshima, Toshiaki Sakamoto, Yooichiroh Maruyama, Fumiyuki Ozawa, ...
    2000 Volume 73 Issue 2 Pages 453-464
    Published: 2000
    Released: October 31, 2001
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    In order to gain insight into the mechanism of the regioselective formation of alkenes in the palladium-catalyzed reductive cleavage of allylic carboxylates or carbonates with formic acid, two types of (η3-1-methylallyl)palladium formates (P1 and P2 types) have been prepared as simple models of catalytic intermediates. The P1 type is a neutral complex coordinated with one tertiary phosphine ligand and a formato ligand: [Pd(η3-MeCHCHCH2)(O2CH)(L)] (L = PMePh2, PMe2Ph, PMe3, P(o-tolyl)3); the P2 type is a cationic complex bearing two tertiary phosphine ligands and a formate counter anion: [Pd(η3-MeCHCHCH2)L2]+CO2H- (L = PMePh2, PMe2Ph, PMe3). The structures and dynamic behavior of the complexes in solution have been examined in detail by NMR spectroscopy. Studies on the thermolysis of the P1 and P2-type complexes have clearly provided the following mechanistic viewpoints: (1) 1-butene and 2-butene are formed from the P1 species; (2) butadiene is liberated from the P2 species; (3) the ratio of 1-butene to 2-butene increases as the bulkiness of phosphine ligand increases. A mechanism involving two geometrical isomers of [Pd(η3-MeCHCHCH2)(H)(L)], which are formed by decarboxylation of the P1-type complexes, has been proposed for the formation of butenes.
  • Jing Ling Zheng, Feng Qi Chen, Takashi Hirano, Yoshihiro Ohmiya, Shoji ...
    2000 Volume 73 Issue 2 Pages 465-469
    Published: 2000
    Released: October 31, 2001
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    A photoreactive analogue of coelenterazine having an azido group was synthesized. The analogue showed similar chemi- and bioluminescence properties to those of the natural coelenterazine. Photolysis of the analogue in the presence of diethylamine gave a derivative azepine as the major product.
  • Kiyoshi Kanie, Yoichiro Tanaka, Kazundo Suzuki, Manabu Kuroboshi, Tame ...
    2000 Volume 73 Issue 2 Pages 471-484
    Published: 2000
    Released: October 31, 2001
    JOURNALS RESTRICTED ACCESS
    Trifluoromethyl ethers R-OCF3 are easily synthesized from the corresponding dithiocarbonates R-OCS2Me (R = aryl or primary alkyl) by a reagent system consisting of 70% HF/pyridine and an N-halo imide. When the reaction is applied to R-OCS2Me wherein R = secondary alkyl, tertiary alkyl, or benzylic group, fluorination leading to the corresponding alkyl fluorides R-F is achieved, whereas a combination of 50% HF/pyridine and N-bromosuccinimide affords the corresponding trifluoromethyl ethers R-OCF3 (R = secondary).
  • Ryoichi Kuwano, Masaya Sawamura, Junya Shirai, Masatoshi Takahashi, Yo ...
    2000 Volume 73 Issue 2 Pages 485-496
    Published: 2000
    Released: October 31, 2001
    JOURNALS RESTRICTED ACCESS
    Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001—0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)-secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
  • Krishanthi Padmarani Jayasundera, Hideki Kinoshita, Katsuhiko Inomata
    2000 Volume 73 Issue 2 Pages 497-505
    Published: 2000
    Released: October 31, 2001
    JOURNALS RESTRICTED ACCESS
    Total syntheses of phycocyanobilin and its derivative bearing a photoreactive group at the D-ring were accomplished by developing a new and efficient method for the construction of A,B-rings component, which consists of the Wittig-type new coupling reaction of 4-(1-methoxyethyl or 1-tosylethyl)-3-methyl-5-tosyl-1,5-dihydro-2H-pyrrol-2-one and a 2-formyl pyrrole derivative in the presence of nBu3P and a base, followed by reduction with aluminum amalgam and a subsequent acid or base treatment.
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