Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
ISSN-L : 0009-2673
Volume 60 , Issue 10
Showing 1-50 articles out of 66 articles from the selected issue
  • Yoshifumi Koide, Masazumi Uchino, Kimiho Yamada
    1987 Volume 60 Issue 10 Pages 3477-3483
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Chelating surfactants bearing hydroxyaminocarbonyl and amino groups (RnAHx) and cotelomer-type surfactants bearing hydroxyaminocarbonyl and pyridyl groups (Ls–VP–Q–Hx) were prepared and applied as flotation collectors for a trace amount of uranium. The uranium in an aqueous solution of pH 4–8 and in seawater was floated more effectively by ion flotation using RnAHx or by foam fractionation using Ls–VP–Q–Hx, compared with alkylhydroxamic acid (RnHx) and telomers bearing hydroxyaminocarbonyl groups (Lo–Hx). The effective flotation was concluded to be due to the chelate effects between the two groups on the complex formation and to the HLB of the resulting complex. Furthermore, the uranium recoveries were examined by using a hydroxamic acid polymer (62Hx), a N-methylhydroxamic acid telomer (Ls5.6MHx), and its cotelomer (Ls3.2VP4.5MHx).
  • Yukihiro Yokoyama, Kensuke Takahashi
    1987 Volume 60 Issue 10 Pages 3485-3489
    Published: 1987
    Released: June 27, 2006
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    The 1H, 13C, and 31P NMR spectra were observed for the title salts in several solvents. The formation of the salts by the deprotonation of the neutral precursors causes significant changes in their NMR parameters. First, the delocalization of the excess charges into the phenyl ring of the salts was confirmed from the 1H and 13C chemical-shift data. Second, the parameters concerned with the center of the anions are dependent on the circumstances of the center atom, phosphorus, such as the hybridization. The results are discussed in terms of the effects of the counter cations and the solvents. Third, a strong polar solvent, HMPA, exerts significant effects on the chemical shifts and the one-bond 13C–31P coupling constants. These parameter changes are explained in terms of an equilibrium between two kinds of ion-pairs (contact ion-pairs and solvent-separated ion-pairs). The parameters obtained in this solvent, HMPA, correspond to those of the solvent-separated ion-pairs or the free anions.
  • Tomoaki Hayano, Hisao Takeuchi, Tomoo Miyazaki
    1987 Volume 60 Issue 10 Pages 3491-3497
    Published: 1987
    Released: June 27, 2006
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    The infrared absorption frequency and intensity of the ν1 vibration, referring to the C–H stretching of chloroform vapor, have been calculated from the theoretical potential energy and dipole-moment functions determined by an ab initio molecular orbital calculation. The selection effect of a Gaussian basis set in the ab initio MO method on the calculated frequency and intensity has been studied. It has been pointed out that the theoretical dipole-moment function is sensitive to a slight displacement of the chlorine in the ν1 vibrational mode.
  • Kengo Imamura, Takashi Nogami, Yasuhiko Shirota
    1987 Volume 60 Issue 10 Pages 3499-3504
    Published: 1987
    Released: June 27, 2006
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    The phase transitions of a series of 1-alkyl-1-azoniabicyclo[2.2.2]octane bromides were studied on the basis of DSC, the measurements of the ionic conductivities of the bromide anion, and Raman spectroscopy. Most of the materials exhibited three endothermic signals at Tc1, Tc2, and Tc3 (Tc1<Tc2<Tc3) when they were heated. The temperature dependence of the ionic conductivities of the bromide anion showed conductivity jumps by a factor of 2–4 at around Tc3. In order to clarify the phase transition, the temperature dependences of the Raman spectra were measured. It was found that the phase transition at Tc1 is caused by the molecular rearrangement in the solid, while the transitions at Tc2 and Tc3 are caused by both the conformational change in the alkyl chain and the rotational motion of the ABCO portion.
  • Sanyo Hamai
    1987 Volume 60 Issue 10 Pages 3505-3508
    Published: 1987
    Released: June 27, 2006
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    The equilibrium constants for the hydrogen bonding between N-phenyl-1-naphthylamine (NPNA) and proton acceptors (1,4-dioxane, nitriles, esters, and amines) in cyclohexane and the corresponding thermodynamic parameters have been determined. The fluorescence of NPNA is quenched by nitriles, esters, and amines. In the cases of nitriles and esters, the quenching is caused by compounds in which a cyano or carboxyl group is conjugated with a double bond. The rate constants for quenching of the NPNA fluorescence by methyl tiglate, methyl 3,4,5-trimethoxybenzoate, and 2,4,6-trimethylpyridine are 81, 73, and 69% of those by methyl acrylate, methyl benzoate, and pyridine, respectively. These findings can be interpreted in terms of the charge-transfer interaction through the hydrogen bond between NPNA (an electron donor) and the proton acceptors (electron acceptors) except for the amines, for which a mechanism different from the charge-transfer mechanism may be important in explaining the fluorescence quenching.
  • Yuji Wada, Akira Morikawa
    1987 Volume 60 Issue 10 Pages 3509-3513
    Published: 1987
    Released: June 27, 2006
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    2-Propanol was catalytically converted to acetone on niobium oxide supported on porous Vycor glass in the presence of oxygen or nitrogen monoxide under UV irradiation. The light of wavelength shorter than 300 nm was effective for the reaction. The VIS-UV absorption measurements showed that niobium oxide was reduced by 2-propanol under the irradiation and Nb4+ formed by the photoreduction was reoxidized by oxygen. The kinetics of the reoxidation was investigated by means of spectroscopic measurements. The redox mechanism is proposed for the photocatalytic oxidation of 2-propanol.
  • Yukio Kobayashi, Yoshio Matsunaga
    1987 Volume 60 Issue 10 Pages 3515-3518
    Published: 1987
    Released: June 27, 2006
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    A series of N,N′-dialkanoyl-2,3,5,6-tetrakis(alkanoyloxy)-1,4-benzenediamines has been prepared and found to be mesogenic over a wide temperature range. The transformation into an isotropic liquid at a temperature between 189 and 209 °C is followed by thermal decomposition. The X-ray diffraction pattern of unoriented specimens in the mesophase consists of two sharp inner peaks and a broad outer one assignable to 100, 110, and 001 reflections respectively, indicating that the phase is hexagonal columnar.
  • Hitoshi Tanaka, Mitsuo Koshi, Hiroyuki Matsui
    1987 Volume 60 Issue 10 Pages 3519-3523
    Published: 1987
    Released: June 27, 2006
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    Thermal decomposition of silane highly diluted in argon was studied behind incident shock waves at the temperatures ranging from 1250 to 1600 K. The decomposition course was followed by monitoring the infrared emission of silane at 4.4 μm. It was confirmed that the effects of consecutive reactions on the decay rate of silane were negligible under our experimental conditions. The unimolecular rate constants obtained directly from the decay curve of silane were found to be smaller than previous experimental values but consistent with the result of the recent trajectory-RRK calculation. It was also found that the addition of molecular hydrogen or nitrogen monoxide to the reactant mixtures had no effect on the decomposition rate of silane.
  • Masaaki Tabata, Isao Yamada
    1987 Volume 60 Issue 10 Pages 3525-3528
    Published: 1987
    Released: June 27, 2006
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    The formation of molecular complexes of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (H2tspp) with cation–18-crown-6 (M(18C6)) has been studied spectrophotometrically at I=0.1 mol dm−3 (MX and MX2, M: Na+, K+, Cs+, NH4+, Ca2+, Sr2+, Ba2+, X: NO3, Cl, Br, I, SCN), and pH 7.0 (N,N′-bis(2-sulfonatoethyl)piperazine: PIPES buffer, 2.0×10−3 mol dm−3). The absorption spectrum of H2tspp considerably changed in the presence of both cation and 18-crown-6, but not in the absence of either of them. The formation constants (logK) of the molecular complexes (M(18C6)·H2tspp) were found to be 2.17±0.05, 2.31±0.03, 2.45±0.03, 2.58±0.02, 1.94±0.03, 2.07±0.02, and 2.12±0.02 for Na+, K+, Cs+, NH4+, Ca2+, Sr2+, and Ba2+, respectively at 25.0±0.5 °C and I=0 mol dm−3. Thermodynamic parameters ΔH/(kJ mol−1) and ΔS/(J K−1 mol−1) are −19.9, −25.0; −33.0, −66.0; −29.3, −50.8; −48.5, −113.7; −21.9, −34.2 and −32.5, −68.0 for Na+, K+, Cs+, NH4+, Sr2+, and Ba2+. The enthalpy changes are linearly correlated to the entropy changes. The equilibrium studies show that charge transfer between M(18C6) and porphyrin π-system is a driving force for the formation of the molecular complex (M(18C6)·H2tspp) as well as hydrophobic interaction.
  • W. Robert Scheidt, C. W. Eigenbrot, Motoyasu Ogiso, Keiichiro Hatano
    1987 Volume 60 Issue 10 Pages 3529-3533
    Published: 1987
    Released: June 27, 2006
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    The synthesis and molecular structure of the title complex was investigated as part of our work into the chemical significance of atropisomerism in porphyrin compounds. The complex crystallizes in the triclinic system, space group P\bar1, a=11.707 (2) Å, b=12.744 (5) Å, c=9.521 (2) Å, α=102.60 (3)°, β=101.31 (2)°, and γ=100.29 (2)°, Z=1. A total of 3737 reflections (average of two forms) were considered observed and used in the solution and refinement of the structure. The structure was refined to a final R=0.081. The molecule, with a crystallographically imposed inversion center, has disordered nicotinamide side chains. This disorder leads to some ambiguity in defining the relative substitution pattern of the phenyl rings. Independent of the assumptions used to define the disorder, the nicotinamide side chains are found to coordinate the zinc ions of adjacent molecules to form a polymeric, linear chain containing six-coordinate zinc ions. The average equatorial Zn–N bond distance is 2.052 (3) Å and the unique axial bond distance is 2.432 (5) Å.
  • Tadashi Hata, Yuji Ohashi, Yoshio Sasada
    1987 Volume 60 Issue 10 Pages 3535-3539
    Published: 1987
    Released: June 27, 2006
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    The crystal structure of the title compound was determined by X-ray diffraction techniques. The final R index was found to be 0.072 for 1187 reflections. The torsional angles of the 2-phenylpropionic acid moiety were comparable to those in other antiinflammatory arylpropionic acids. Force-field energy calculations suggested that the α-methyl substituent to the carboxyl group restricts the rotation of the benzene ring about the Cα-phenyl bond. This restricted conformation may be related to the antiinflammatory activity.
  • Akito Kurosaki, Tetsuhiro Okuyama, Susumu Okazaki
    1987 Volume 60 Issue 10 Pages 3541-3545
    Published: 1987
    Released: June 27, 2006
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    A surface treatment of niobic acid using about l mol dm−3 of phosphoric acid was effective for the enhancement of the surface acidity and the catalytic activity for some acid-catalyzed reactions such as cyclohexanol dehydration and alkylation of benzene with methanol. However, a treatment with phosphoric acid of higher concentration might form a deposit on the surface, which would prevent the penetration of reactants and/or products and, thus, decreased the catalytic activity of niobic acid. The P component added to the niobic acid was hardly removed by steaming at 400 °C, although it could be taken off by soaking in water at room temperature for twelve hours.
  • Masatatu Suzuki, Akira Uehara, Hiroki Oshio, Kazutoyo Endo, Makoto Yan ...
    1987 Volume 60 Issue 10 Pages 3547-3555
    Published: 1987
    Released: June 27, 2006
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    Dinuclear iron(II, II) complexes, [Fe2(L-py)(RCOO)2]BF4·nH2O (RCOO : CH3COO (1a) and C6H5COO (2a)), and two types of dinuclear mixed valence iron(II, III) complexes [Fe2(L-py)(RCOO)2](BF4)2·nH2O (RCOO : CH3COO (1b) and C6H5COO (2b)) and [Fe2(L-py)(CH3COO)(OH)](BF4)2·2H2O (3) were prepared, where L-py represents 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methyl-phenolate(1–). Only one of the two iron(II) ions in the iron(II, II) complexes is easily oxidized with molecular oxygen in methanol to form the mixed valence complexes, [Fe2(L-py)(RCOO)2](BF4)2·nH2O, which were characterized by chemical analyses and Mössbauer measurements. Magnetic susceptibility measurements over the temperature range 80–300 K revealed that high-spin iron(II) and iron(III) ions are antiferromagnetically coupled with the spin-exchange coupling constants J=−3–−8cm−1. The complexes exhibited an ESR signal of gav≈1.7 near liquid helium temperature. Such an ESR signal arises from an antiferromagnetically spin-coupled high-spin iron(II, III) dimer. An inter-valence charge-transfer transition was observed in the region 7000–8500 cm−1. The electron delocalization parameter α is estimated to be ca. 0.08, which corresponds to the class II mixed valence type in the classification of Robin and Day. Cyclic voltammogram of the complex 2b in acetonitrile showed two reversible couples at +0.05 and +0.73 V (vs. SCE), which were assigned to the redox reactions of Fe(II, III)/Fe(II, II) and Fe(III, III)/Fe(II, III), respectively. The comproportionation constants of 1b and 2b at 20 °C are 1.6×1012 and 5.0×1011, respectively, implying that the present mixed valence complexes are significantly stabilized.
  • Hiromichi Yamada, Miyuki It\={o}, Masateru Mizuta
    1987 Volume 60 Issue 10 Pages 3557-3562
    Published: 1987
    Released: June 27, 2006
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    The extraction of copper(II) with cyclohexanecarboxylic acid in benzene was carried out at 25 °C and at the aqueous ionic strength of 0.1 mol dm−3 (NaClO4). The partition constant, KD,HA of cyclohexanecarboxylic acid between benzene and water, and the dimerization constant, K2,HA of cyclohexanecarboxylic acid in benzene were determined: logKD,HA=0.90 and logK2,HA=1.54, respectively. The monomeric and dimeric copper(II) cyclohexanecarboxylates were responsible for the extraction:
    Cu2++(HA)2,o \ ightleftharpoons (CuA2)o+2H+
    Cu2++2(HA)2,o \ ightleftharpoons (CuA2(HA)2)o+2H+
    2Cu2++2(HA)2,o \ ightleftharpoons (Cu2A4)o+4H+
    2Cu2++3(HA)2,o \ ightleftharpoons (Cu2A4(HA)2)o+4H+
    with the extraction constants, logKex(10)=−8.34, logKex(12)=−7.33, logKex(20)=−12.47, and logKex(22)=−11.73, respectively. By comparing the overall formation constant of the dimeric copper(II) cyclohexanecarboxylate, Cu2A4(HA)2 in the aqueous phase with that of copper(II) decanoate and lipoate, the cyclohexane ring was found to inhibit the formation of the dimeric copper(II) carboxylate.
  • Hideo Kurosawa, Aki Tsuboi, Yoshikane Kawasaki, Masanori Wada
    1987 Volume 60 Issue 10 Pages 3563-3567
    Published: 1987
    Released: June 27, 2006
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    Neutral and cationic 1-3-η-(2-methylallyl) complexes of Pd and Pt containing tris(2,6-dimethoxyphenyl)phosphine (abbreviated as P(2,6)3), M(1-3-η-CH2CMeCH2)Cl{P(2,6)3} and [M(1-3-η-CH2CMeCH2){P(2,6)3}]BF4, were prepared. The latter contained a weakly coordinated OMe group of P(2,6)3 which was readily replaced by carbon monoxide to afford [M(1-3-η-CH2CMeCH2)(CO){P(2,6)3}]BF4. Owing to large steric bulk and high nucleophilicity of P(2,6)3, addition of P(2,6)3 to these complexes did not result in coordination of the second molecule of the phosphine to the metal atom but ready attack at the metal-bound 2-methylallyl and methoxyl carbon atoms to give the corresponding (2-methylallyl)phosphonium and methylphosphonium ions. From these reactions were isolated a neutral 1-3-η-(2-methylallyl)platinum(II) complex involving chelate coordination of a tertiary phosphine ligand which was derived from the loss of methyl of one methoxyl group in P(2,6)3 and the resulting phenoxo ligand, and a cationic, binuclear Pt(I) carbonyl complex bridged by the 2-methylallyl group. Also prepared in this study were 1-3-η-(2-methylallyl)(acetylacetonato) complexes of Pd and Pt, M(1-3-η-CH2CMeCH2)(acac){P(2,6)3}. In the platinum analog, the acetylacetonato ligand was suggested to coordinate to the metal in a monodentate fashion via the central carbon atom. Both complexes afforded moderate yields of CH2=CMeCH2CH(COMe)2 upon treatment with carbon monoxide, while the reaction of M(1-3-η-CH2CMeCH2)(CO){P(2,6)3}+ with sodium acetylacetonate failed to give the same coupling product.
  • Yutaka Fukuda, Keiko Yamagata, Thomas A. Kaden
    1987 Volume 60 Issue 10 Pages 3569-3574
    Published: 1987
    Released: June 27, 2006
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    A new series of nickel(II) complexes containing 1,4-diazacycloheptane-N,N′-dicarboxylates (dachdx, where x=a means the acetate derivative, x=m, e, and p are the α-methyl, α-ethyl, and α-propyl substituents of the carboxyl side chain, respectively) were prepared as solids, Ni(dachdx)Ln (L=H2O or pyridine, n=0, 1, or 2). These complexes can be classified according to their geometry into three types: (1) Octahedral [Ni(dachda)(H2O)2], (2) square planar [Ni(dachdx)](x=m, p, or e) and (3) penta-coordinate [Ni(dachdm)(py)]. In the solid state the strength of the bonds between the metal ion and the carboxylate groups increases in the order: Octahedral<penta-coordinate<square planar. In solution, some of these compounds show chromotropic behavior, e.g. solvatochromism, thermochromism, and inert salt or active salt effects. The stability constants of the Ni2+ complexes were determined by pH-titrations and spectrophotometry. The following equilibria were found:
    [Ni(aq)]2++dachdx2−\ ightleftharpoons[Ni(dachdx)];
    [Ni(dachdx)]+X\ ightleftharpoons[Ni(dachdx)X];
    where X=NCS, Cl, or Br. It is shown that the substituent of the carboxylate side chain plays an important steric role, thus determining the value of the stability constant of [Ni(dachdx)].
  • Kaoru Horiuchi, Masahiro Mikuriya, Hisashi Okawa, Sigeo Kida
    1987 Volume 60 Issue 10 Pages 3575-3580
    Published: 1987
    Released: June 27, 2006
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    A pentadentate salen analog with a pendant thioether group, N,N′-disalicylidene-2-methyl-4-ethylthio-1,2-butanediamine (H2L), formed two types of cobalt(III) complexes, [Co(L)]ClO4·H2O (1) and [Co(L)NH3]PF6·H2O (2). Based on infrared and electronic spectra, the complex 1 was revealed to have a square-pyramidal configuration with the pendant sulfur coordination at the apex. The structure of the complex 2 was determined by single-crystal X-ray analysis. The molecule has a six-cooridnate structure with the coordination of the pendant sulfur and the ammonia molecule at the apical sites, the Co–S and Co–N(NH3) distances being ca. 2.25 and 2.0 Å, respectively. Electrochemical measurements (CV and DPP) for 2 and [Co(salen)(R-NH2)2]PF6 as the reference have revealed that the substitution of thioether sulfur for one of the apical amine ligands results in a positive shift of the CoIII/CoII redox potential. It is also found that the CoIII/CoII reduction of five-coordinate 1 occurs at a significantly high potential compared with six-coordinate 2 and [Co(salen)(R–NH2)2]PF6.
  • Jun-ichi Aihara
    1987 Volume 60 Issue 10 Pages 3581-3584
    Published: 1987
    Released: June 27, 2006
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    Large compact polycyclic aromatic hydrocarbons (PAHs) are photochemically very stable. These PAHs have been considered as excellent candidates for explaining the interstellar infrared emission lines. Since the large compact PAHs exhibit the first electronic absorption band in a rather low-energy region, it is possible and very probable that fluorescence from such PAHs are responsible for the red emission humps of several nebulae such as the Red Rectangle, a nebula surrounding the binary star HD 44179.
  • Toru Ozeki, Kazuko Murata, Hiroshi Kihara, Seiichiro Hikime
    1987 Volume 60 Issue 10 Pages 3585-3589
    Published: 1987
    Released: June 27, 2006
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    When alkali metal or alkaline earth metal chloride, (except magnesium chloride) was added to a solution of sodium molybdate, similar Raman spectra were observed. When magnesium chloride was added to the molybdate solution, however, the intensity of the peak (ν1) based on the symmetric stretching vibration of the tetrahedral molybdate decreased and a new peak (νx) appeared at a higher wavenumber than ν1. The wavenumber of the new peak is almost equal to that observed for solid magnesium molybdate. This suggests that the new peak can be ascribed to the molybdates of the distorted octahedral structure, since the molybdate ion exists as an octahedral in the solid state of magnesium molybdate. The tetrahedral and the octahedral molybdates seem to be in equilibrium in the solution.
  • Tomokazu Matsue, Atsushi Aoki, Isamu Uchida, Tetsuo Osa
    1987 Volume 60 Issue 10 Pages 3591-3595
    Published: 1987
    Released: June 27, 2006
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    The interaction of several electroinactive cationic drugs (hexamethonium, quinidine, neostigmine, nicotine and acetylcholine) with Nafion and the applicability of Nafion-coated electrodes to determination of the drugs have been investigated. The addition of a drug to an electrolyte solution containing (ferrocenylmethyl)trimethylammonium (FA+) induced a decrease in the peak current and a shift in the apparent half-wave potential of a cyclic voltammogram for FA+. The decrease in the peak current has been used for determination of the drugs at low concentrations less than 10−3 mol dm−3. The ion-selectivity coefficients of Nafion for the drugs have been determined by an electrochemical method. These drugs showed quite large values and the values seemed to be dependent on the hydrophobicity of the drugs.
  • Atsushi Kijima, Shizen Sekiguchi
    1987 Volume 60 Issue 10 Pages 3597-3601
    Published: 1987
    Released: June 27, 2006
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    The kinetics of the alkaline hydrolysis of N-methyl-2,4-dinitroacetanilide (2), N-ethyl- (3), and N-methyl-N-(5-nitro-2-pyridyl)acetamide (4) was carried out. The reaction path consists of two stages: the first one is the rate-limiting formation of the first tetrahedral intermediate (monoanionic) and the second one the fast decomposition of the intermediate. The latter fast decomposition of the intermediate (monoanionic) involves two processes: one is the direct decomposition of the intermediate to the products and the other is a proton abstraction of the hydroxyl group of the intermediate by OH giving the second tetrahedral intermediate (dianionic), followed by its deconposition to the products. For the alkaline hydrolysis of 24, the decomposition of the first intermediate occurred predominantly via the latter process.
  • Seiji Yamaguchi, Mayumi Takai, Isao Hanazome, Yûko Okada, Yoshiy ...
    1987 Volume 60 Issue 10 Pages 3603-3605
    Published: 1987
    Released: June 27, 2006
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    One step cyclization of 2′,4′,6′-trihydroxyacetophenone with 1,4-dibromo-2-methyl-2-butene gave two 2-isopropenyl-2,3-dihydrobenzofuran-4,6-diols and a new 3-methyl-2,5-dihydro-1-benzoxepin-6,8-diol. The structure of natural remirol was confirmed by comparison with monomethylated compounds of the former products. Racemic remirol was synthesized from 3,5-dimethoxyphenol in three steps.
  • Kohji Suda, Toshio Tsujimoto, Masashige Yamauchi
    1987 Volume 60 Issue 10 Pages 3607-3611
    Published: 1987
    Released: June 27, 2006
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    Substituent effects on the chemical shifts of the conjugation sites in α-phenyl-N-arylnitrones (2) have been investigated. Resonance effects predominate at these positions. The electronic effects of the substituents should be treated separately between electron-donating groups and electron-withdrawing ones. A plausible mechanism for the transmission of the substituent effects in 2 has been proposed.
  • Hideo Kise, Hitoshi Shirato, Hidetaka Noritomi
    1987 Volume 60 Issue 10 Pages 3613-3618
    Published: 1987
    Released: June 27, 2006
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    N-Acetylated aromatic amino acids were esterified by α-chymotrypsin suspended in alcohols. The reaction rate and the yields of the esters depended primarily on the amount of the aqueous buffer solution in which α-chymotrypsin was dissolved. The reaction rate increased but the equilibrium yield of the esters decreased with increasing concentration of water. High substrate selectivity and stereospecificity were observed for L-aromatic amino acids; and therefore, in this system α-chymotrypsin was considered to be an effective catalyst which maintains its native conformation. When the amount of the substrate was increased, the present reactions gave higher yields of the esters than the reactions in chloroform (two-phase method).
  • Fumio Moriwaki, Hiromi Kaneko, Akihiko Ueno, Tetsuo Osa, Fumio Hamada, ...
    1987 Volume 60 Issue 10 Pages 3619-3623
    Published: 1987
    Released: June 27, 2006
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    Host–guest complexation of β-Cyclodextrin bearing two naphthyl moieties (1) has been studied by circular dichroism and fluorescence spectroscopic methods. The circular dichroism spectrum exhibits a positive band around 225 nm while the fluorescence spectrum exhibits a predominant monomer peak with a shoulder of excimer emission. These data suggest that 1 can take two forms, one of two naphthyl moieties being included in the cavity of the predominant form (A) while both naphthyl moieties being located outside of the cavity in another form (B). With increasing concentration of guests, the dichroism intensity diminishes but the excimer intensity increases. This result indicates that 1 moves the included naphthyl moiety outward from the interior of the cavity during guest binding and then the two naphthyl moieties act as hydrophobic caps. The binding of 1 was stronger for cyclohexanol and 1-adamantanecarboxylic acid but weaker for cyclododecanol than that of the corresponding γ-cyclodextrin derivative in correspondence with size-fitting between the guests and hosts.
  • Kazunari Taira, David G. Gorenstein
    1987 Volume 60 Issue 10 Pages 3625-3632
    Published: 1987
    Released: June 27, 2006
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    Ab initio molecular orbital calculations have been performed on the reaction profile for the addition/elimination reaction between ammonia and formic acid, proceeding via a tetrahedral intermediate: NH3+HCO2H→H2NCH(OH)2→NH2CHO+H2O. For the addition of ammonia two transition state conformations, of which one possesses a lone pair, on the hydroxyl oxygen of formic acid, antiperiplanar to the attacking nitrogen (T1 conformer) and the other possesses a hydrogen atom, of the OH group, antiperiplanar to the nucleophile ammonia (T1′ conformer), have been identified as characteristic transition state structures. Calculated transition state energies for the first addition step of the reaction revealed that a lone pair on the oxygen of the OH group, which is antiperiplanar to the attacking nitrogen (T1 conformer), stabilized the transition state by 7.4 kcal mol−1 compared to the T1′ conformer. Similarly, for the second water elimination step of the reaction, two conformers (T2 and T2′) have been identified as transition state structures, of which the T2 conformer possesses a lone pair on the nitrogen, antiperiplanar (app) to the leaving water and the T2′ conformer possesses a hydrogen atom, of the NH2 group, app to the leaving water molecule. Again, calculated transition state energies for the T2 and T2′ structures revealed that a lone pair on the nitrogen of the NH2 group, which is app to the scissile C–O bond (T2 conformer), stabilized the transition state by 3.1 kcal mol−1, thus supporting the hypothesis of stereoelectronic control for this reaction. The significance of these stereoelectronic effects for the mechanism of action of serine proteases is discussed and a novel mechanism is proposed.
  • Shigeru Sugiyama, Tohru Tsuda, Akira Mori, Hitoshi Takeshita, Mitsuaki ...
    1987 Volume 60 Issue 10 Pages 3633-3638
    Published: 1987
    Released: June 27, 2006
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    Thermal reactions of tropone with furan and 2-methoxyfuran mainly gave the endo-[4+2] cycloadducts, the kinetically controlled products, at 3000 bar. In the latter case, the product further reacted with tropone to yield 2:1-adducts. On the other hand, the reaction with 3,4-dimethoxyfuran under similar conditions yielded mainly the exo-[4+2] adducts, the thermodynamically controlled products. The predominant formation of the endo-Diels–Alder adducts with furans under the high-pressure conditions may be valuable from a synthetic point of view.
  • Takashi Matsumoto, Sachihiko Imai, Takashi Yoshinari
    1987 Volume 60 Issue 10 Pages 3639-3643
    Published: 1987
    Released: June 27, 2006
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    In order to elucidate the absolute configuration of C-15 in natural lycoxanthol, (15R)-11,16-dihydroxy-12-methoxymethoxy-8,11,13-abietatrien-7-one and its (15S)-epimer were transformed into (15R)-12,16-epoxy-6,11,14-trihydroxy-5,8,11,13-abietatetraen-7-one (1a) and its (15S)-epimer, respectively. The synthetic 1a was identical with natural lycoxanthol. Thus, the stereochemistry of C-15 in the natural compound was conclusively assigned as R-configuration.
  • Kiyoshi Matsumoto, Takane Uchida, Yukio Ikemi, Toshio Tanaka, Momoyo A ...
    1987 Volume 60 Issue 10 Pages 3645-3653
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Pyridinium and diazinium dicyanomethylides underwent 1,3-dipolar cycloaddition-extrusion reactions with phenylsulfinylethene, producing the corresponding 3-cyanoindolizines in moderate to good yields. 1,3-Dipolar cycloadditions of these ylides with bis(trimethylsilyl)ethyne gave either the 1,2-bis(trimethylsilyl)-3-cyanoindolizines or the 1-trimethylsilyl-3-cyanoindolizines, or mixtures of these, depending on the substituents and the presence of another nitrogen atom in the pyridine ring. 1,2-Bis(trimethylsilyl)-3-cyanoindolizines underwent regiospecific protodesilylation at the 2-position upon a treatment with silica gel in refluxing chloroform, yielding 1-trimethylsilyl-3-cyanoindolizines. The 1,2-bis(trimethylsilyl)-, and 1-trimethylsilyl-3-cyanoindolizines suffered from quantitative protodesilylation under catalysis by tetrabutylammonium fluoride to afford 1,2-unsubstituted 3-cyanoindolizines.
  • Kazuhiko Saigo, Hiroki Kimoto, Hiroyuki Nohira, Kazunori Yanagi, Masak ...
    1987 Volume 60 Issue 10 Pages 3655-3658
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The Crystal structures of (+)-1-phenylethylamine·cinnamic acid salt and (+)-1-(4-isopropylphenyl)ethylamine·cinnamic acid salt were determined by X-ray analysis. The crystal structures of these two salts provided for the first time some insights into the mechanism of the formation of a conglomerate crystal. In each crytal, two amine components and two acid components form a helical column by hydrogen bonds. On the basis of this similarity in the molecular arrangements, the role of cinnamic acid, an achiral acid, is discussed, and the criteria for the choice of an achiral acid in the transformation of the racemic modification of an amine into a conglomerate crystal is proposed.
  • Shigeyoshi Kanoh, Hiroki Muramoto, Natsumi Kobayashi, Masatoshi Motoi, ...
    1987 Volume 60 Issue 10 Pages 3659-3662
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Racemic 6,6′-dimethylbiphenyl-2,2′-dicarboxylic acid (1) could be conveniently synthesized and efficiently resolved by the recrystallization of the brucine salts in satisfactory yields. Each enantiomer, thus obtained, was confirmed to be optically pure from a high-performance liquid chromatographic (HPLC) analysis on an optically active column.
  • Ichiro Okura, Katsumi Kurabayashi, Shigetoshi Aono
    1987 Volume 60 Issue 10 Pages 3663-3666
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The regeneration of nicotinamide–adenine dinucleotide phosphate (reduced form, NADPH) by the reduction of NADP by hydrogen gas was carried out with the [hydrogenase–ferredoxin-NADP reductase (FNR)] system. Ketone hydrogenation was tried by the combination of the above system and alcohol dehydrogenase (ALDH), as shown in the following scheme:
    (Remark: Graphics omitted.)
    In the [hydrogenase–FNR] system, NADP was easily reduced by hydrogen to form NADPH. By adding ALDH to the above system, the hydrogenation of ketone to alcohol was observed. The ketones used in this study were 2-butanone, 2-pentanone, and 2-hexanone. After 8 h, the turnover number of NADP was 13 for 2-butanone, 15 for 2-pentanone, and 10 for 2-hexanone, showing a recurrence of NADP by hydrogen gas.
  • Kin-ichi Tadano, Yukinori Hotta, Masahiro Morita, Tetsuo Suami, Bryan ...
    1987 Volume 60 Issue 10 Pages 3667-3671
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    (−)-8a-epi-Swainsonine (4), one of the stereocongeners of physiologically interesting indolizidine alkaloid (−)-swainsonine (1), has been synthesized starting from known methyl 3-azido-4,6-O-benzylidene-3-deoxy-α-D-altropyranoside. The α-D-mannosidase inhibitory activity of 4 was compared with natural 1.
  • Kin-ichi Tadano, Hiroshi Kimura, Masahide Hoshino, Seiichiro Ogawa, Te ...
    1987 Volume 60 Issue 10 Pages 3673-3678
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The known 3-O-benzyl-D-xylose was converted into methyl (4R,5R,6R)-4,6,7-triacetoxy-5-benzyloxy-2-(methoxycarbonyl)heptanoate (8) by employing Knoevenagel condensation of 2,4,5-tri-O-acetyl-3-O-benzyl-aldehydo-D-xylose with dimethyl malonate as a key reaction. O-Deacetylation of 8 and successive glycol cleavage followed by acetylation gave a mixture of (1S,4R,5R,6R)-5-acetoxy-6-benzyloxy-4-methoxycarbonyl-2-oxobicyclo[2.2.1]heptan-3-one and dimethyl (2R,3R,4S)-2,4-diacetoxy-3-benzyloxy-1,1-cyclopentanedicarboxylate (12), which was converted into 12 exclusively. This enantiomerically pure highly oxygenated cyclopentane dicarboxylate 12 was converted into (3S,4S)-3-benzyloxy-1-(t-butyldiphenylsilyloxymethyl)-4-hydroxy-1-cyclopentene (15) by 1) thermal demethoxycarbonylation accompanied by β-elimination of the acetoxyl group, 2) diisobutylaluminium hydride reduction, and 3) selective protection of thus formed 1-cyclopentene-1-methanol. Pyridinium chlorochromate oxidation of 15 followed by reduction with sodium borohydride gave a 6.4:1 mixture of (3S,4R)-3-benzyloxy-1-(t-butyldiphenylsilyloxymethyl)-4-hydroxy-1-cyclopentene (18) and 15. Hydroboration of O-desilyl derivative of 18 proceeded stereoselectively from the less hindered α-face, and (1R,2R,3R,4R)-2,4-diacetoxy-1-acetoxymethyl-3-(benzyloxy)cyclopentane (21) was obtained after acetylation. Deprotection of 21 gave pseudo-β-D-arabinofuranose.
  • Seiji Shinkai, Seiichi Mori, Koji Araki, Osamu Manabe
    1987 Volume 60 Issue 10 Pages 3679-3685
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The pKa of Phenol Blue shifted from 4.6 to 6.2 because of complexation of protonated Phenol Blue in the cavity of hexasulfonated calix[6]arene with dodecyl substituents (2C12). The finding stimulated us to examine whether the analogs (2C) suppress the dediazoniation of arenediazonium ions in an aqueous system as crown ethers do in organic solvents. We have found that 2C can suppress the dediazoniation in an aqueous system where neither 18-crown-6 nor anionic micelles are effective. The magnitude of the inhibition effect was 4–5 fold. The reaction rate of the diazo coupling with N,N-dimethylaniline was significantly suppressed in the presence of 2C, suggesting that arenediazonium ions are deactivated through complexation with 2C. The novel stabilization effects were explained by the strong anionic reaction field which neither 18-crown-6 nor anionic micelles have: that is, 2C has a peculiar architecture that six sulfonato groups are circularly arranged on the edge of the calixarene cavity.
  • Masayuki Kameyama, Nobumasa Kamigata
    1987 Volume 60 Issue 10 Pages 3687-3691
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The asymmetric addition of trichloromethanesulfonyl chloride to styrene in the presence of a catalytic amount of a ruthenium(II) complex with chiral ligands, Ru2Cl4[(−)-diop]3 or Ru2Cl4[(+)-diop]3, proceeds under mild conditions to give optically active 1:1 adducts, 1,1,1,3-tetrachloro-3-phenylpropane (2), with the extrusion of sulfur dioxide. When (−)-DIOP or (+)-DIOP was used as a chiral ligand of the ruthenium(II) complex, (R)-(+)-(2) or (S)-(−)-(2), was obtained with about 10% enantiomeric excess, respectively. A reaction mechanism involving a radical redox transfer mechanism was proposed; the asymmetric induction was attributed to the restricted configuration of the radical intermediates confined in the coordination sphere of the ruthenium complex with chiral ligands.
  • Kunihisa Yoshida, Hirohito Kitabayashi
    1987 Volume 60 Issue 10 Pages 3693-3696
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The electrooxidation of several 1-methylimidazoles was performed in MeOH that contains NaCN at a platinum anode in a divided cell. Replacement of an aromatic hydrogen by a cyano group occurred. With 1,2,4,5-tetramethylimidazole, the 2,5-addition of cyano groups to the imidazole ring was achieved, and besides side-chain substitution occurred concurrently.
  • Nobuto Minowa, Teruaki Mukaiyama
    1987 Volume 60 Issue 10 Pages 3697-3704
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    A chiral allylating agent, readily generated from tin(II) trifluoromethanesulfonate (tin(II) triflate), chiral diamines derived from (S)-proline and allylaluminum, is efficiently employed in the asymmetric allylation of aldehydes and an epoxide. Reaction of a chiral 2-methyl-2-propenylating (methallylating) agent with aldehydes also proceeds smoothly to afford the corresponding homoallylic alcohols in good yields with high enantioselectivities. According to a similar procedure, asymmetric propargylation of aldehydes affords homopropargylic alcohols in good optical purities.
  • Iwao Tabushi, Tatsuya Nabeshima, Kazuo Yamamura, Haruo Fujita
    1987 Volume 60 Issue 10 Pages 3705-3711
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Two-dimensional (2D) NMR spectroscopies, proton (400 MHZ)– proton (400 MHz) and carbon (100 MHz)– proton (400 MHz) chemical shift correlation spectroscopy, were developed as a reliable technique for the strict assignment of crowded and complicated NMR absorptions of substituted cyclodextrin derivatives, pentakis[2,6-O-(t-butyldimethylsilyl)]-A,B-bis-[2-O-(t-butyldimethylsilyl)-6-deoxy-6-(methylthio)]-β-cyclodextrin (2) and A,B-bis[6-deoxy-6-(methylthio)]-β-cyclodextrin (1).
  • Akikazu Kakehi, Suketaka Ito, Yasuhiro Ohno, Shouji Shiba, Sakashi Kam ...
    1987 Volume 60 Issue 10 Pages 3713-3720
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    2-Ethoxycarbonyl-3-methyl- and 3-phenylthieno[2,3-b]indolizine derivatives were first synthesized in moderate to good yields by the treatment of tricyclic 5,5a-dihydropyrido[2,1-c]thieno[3,2-e][1,4]thiazines with a dehydrogenating agent. In contrast to the cases of bicyclic 1,9a-dihydropyrido[2,1-c][1,4]thiazines, all of the thienoindolizines obtained here were rearranged products and no desulfurized product could be obtained.
  • Shin-ichi Takekuma, Yoshiharu Matsubara, Hiroshi Yamamoto, Tetsuo Nozo ...
    1987 Volume 60 Issue 10 Pages 3721-3730
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Autoxidation of the title azulenes at 100 °C in HMPA or DMF afforded a wide variety of products: Namely, the oxidation products of the side-chains, 1-substituted azulenes, 1H-inden-1-ols, naphthoquinones, benzenoids, and dimeric and trimeric compounds, with or without rearrangements. 1H NMR (200-MHz) parameters of various azulene derivatives are given for comparative study. Possible reaction pathways for the formation of these products are discussed in comparison with the results of the previous studies on guaiazulene and 4,6,8-trimethylazulene.
  • Yuji Orihashi, Michinori Nishikawa, Hiroyuki Ohno, Eishun Tsuchida, Hi ...
    1987 Volume 60 Issue 10 Pages 3731-3738
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    A series of tetra- or octasubstituted phthalocyaninatocobalt derivatives were prepared and their oxidation behaviors were examined in relation to the nature of substituents. The oxidation potentials of phthalocyanines, especially those of rings were affected by the nature of both substituents and axial ligands. These oxidation potentials were in a linear relation with the Hammett’s constants for substituents or axial ligands. The electrocrystallization proceeded when an oxidation potential higher than that for the phthalocyanine ring was given to the solution. This potential shift was therefore revealed to be an important factor to control the electrocrystallization of these phthalocyanines.
  • Nobuaki Washida
    1987 Volume 60 Issue 10 Pages 3739-3750
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The reaction of oxygen atoms with propane-1,1,1,3,3,3-d6, (CD3)2CH2, in a fast-flow system was studied with a photoionization mass spectrometer. Isopropyl-d6 radicals, (CD3)2\dotCH, formed by the initial hydrogen abstraction at the 2-position were detected directly.
    (CD3)2CH2+O(3P)→(CD3)2CH+OH (3)
    The subsequent reaction of (CD3)2\dotCH radicals with atomic oxygen proceeds by both an deuterium abstraction (61%) and an oxygen addition reaction (39%). The product in the deuterium abstraction was CD2CHCD3 and those in the oxygen addition were (CD3)2CO (18%) and CD3CHO (21%).
    (Remark: Graphics omitted.)
    Competition experiments show that (CD3)2\dotCH radicals react (0.029±0.004) times as fast with O2 as with O(3P). In the presence of an excess of O2, CD2CHCD3 was observed in decreased yield (20%) and (CD3)2CO and CD3CHO increased to 32 and 44%, respectively. The rate data for Reaction 3 were fitted by an Arrhenius expression:
    k3=(2.0−0.7+1.0)×10−10exp[−(6086±392 cal mol−1)⁄RT]
    cm3 molecule−1 s−1 (381–627 K). The rate constant of Reaction 3 obtained from the yields of products was 7.9×10−15 cm3 molecule−1 s−1 at 298K.
  • Nobuaki Washida, Shiro Hatakeyama
    1987 Volume 60 Issue 10 Pages 3751-3756
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The reaction of oxygen atoms with (CD3)2CHCl in a fast flow system was studied with a photoionization mass spectrometer. The (CD3)2\dotCCl radical formed by the initial hydrogen abstraction at the 2-position was detected directly.
    (CD3)2CHCl+O(3P)→(CD3)2\dotCCl+OH (1)
    The rate data for Reaction 1 were fitted by an Arrhenius expression: k1=(3.5−0.9+1.2)×10−11exp[(−4973±278 cal mol−1)/RT] cm3 molecule−1 s−1 (399–628 K). Among the products formed in the subsequent reaction of (CD3)2\dotCCl radicals with atomic oxygen, CD3CCl=CD2 (31%) produced by the deuterium abstraction and (CD3)2CO (24%) by the oxygen addition were observed. Competition experiments show that (CD3)2\dotCCl radicals react (0.0079±0.0010) times as fast with O2 as with O(3P). In the presence of an excess of O2, CD3CCl=CD2 was observed in decreased yield (3.5%) and (CD3)2CO increased to 56%.
  • Nobuaki Washida
    1987 Volume 60 Issue 10 Pages 3757-3764
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The reaction of oxygen atoms with 2-propanol was studied in a fast flow system coupled with a photoionization mass spectrometer. Radicals formed in the primary attack of O(3P) atoms on 2-propanol were photoionized by the Xe lamp and identified as the (CH3)2\dotC(OH) radical from (CH3)2CH(OH) and (CH3)2CD(OH) and the (CD3)2\dotC(OH) radical from (CD3)2CH(OH). The major primary product in the subsequent reaction of O+(CD3)2\dotC(OH) was found to be acetone, (CD3)2CO, (62±4%). Formation of 1-propen-2-ol, CD3C(OH)=CD2, by deuterium abstraction and acetic acid, CD3COOH, by oxygen addition were observed in the reaction of O+(CD3)2\dotC(OH). In the reaction of 18O+(CD3)2\dotC(OH), the acetone produced was mostly (CD3)2CO. This fact shows that acetone is produced predominantly by the hydrogen abstraction by O(3P) from the O–H in the (CD3)2\dotC(OH) radical. A part of the acetone is produced also by the addition of O(3P) to the (CD3)2\dotC(OH) radical; i.e., a small but significant signal of (CD3)2C18O was observed in the reaction of 18O+(CD3)2\dotC(OH). The competition experiment between O(3P) and O2 for the (CD3)2\dotC(OH) radical shows that (CD3)2\dotC(OH) react (0.16±0.02) times as fast with O2 as with O(3P). This result suggests that the reaction of (CD3)2\dotC(OH) with O2 is very rapid. It is proposed that the rapid reaction is hydrogen abstraction by O2 from the O–H in the (CD3)2\dotC(OH) radical to form acetone and HO2.
  • Walid Ahmad Badawi, H. A. Brown-Acquaye, Ali Esa Eid
    1987 Volume 60 Issue 10 Pages 3765-3769
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Calorimetric studies on the behavior of the heat capacity of bismuth have been carried out in the range 333 to 923 K. Values of the enthalpy and entropy have been determined for selected temperatures. The enthalpy and entropy of fusion at 544.54 K are 11.360±0.014 kJ mol−1 and 20.86±0.03 JK−1 mol−1, respectively. Appropriate polynomial temperature functions of the Cp for solid and liquid bismuth are given. Earlier reported increasing Cp at temperatures above 800 K proved not to be reliable. The heat capacity at constant volume decreased from 25.80 to 21.14 JK−1 mol−1 over the region 544.54 to 873 K. Due to beginning of higher-order transformation, the Cv of solid bismuth showed an excess over the harmonic value (3R).
  • Walid Ahmad Badawi, Ali Esa Eid
    1987 Volume 60 Issue 10 Pages 3771-3774
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Calorimetric studies on the behavior of the enthalpy of formation in the tin–antimony system have been carried out at five different compositions (43.3–55 at -% Sb). The enthalpy of dissolution has been determined at 796.15 and 768.15 K. The enthalpy of formation is negative and takes a maximum value (2.906±0.002 kJ mol−1) at 298.15 K for 50 at-% Sb. The molar enthalpy of mixing is more positive than that of formation. On comparing with partial molar enthalpy of mixing, the partial molar enthalpy of formation of tin is shifted to more negative values, while that of antimony to more positive values.
  • Helena Dodziuk
    1987 Volume 60 Issue 10 Pages 3775-3779
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Recent rapid development of synthetic and theoretical methods has yielded molecules with unusual stereochemistry on carbon atom. One of the most interesting examples of such earlier unsought of arrangements is provided by planar cyclohexane rings. Few molecules of this kind have been synthesized and two others have been postulated on the basis of molecular mechanics calculations. In the present article a critical review of existing experimental and theoretical results is supplemented with a molecular mechanics study of a series of cyclohexanes fused with up to six 3-, 4-, and 5-membered rings causing the flattening of C6 ring. The existing experimental data and the results of the calculations seem to indicate that the flattening is more pronounced when smaller and/or larger number of rings are fused. The applicability and limitations of molecular mechanics with the MM2 parameterization to the study of the flattening of cyclohexane ring have been critically analyzed. The synthetic efforts in this field seem to indicate that some results calculated for hypothetical molecules will be checked in the near future. Similarly to hypothetical [6]asterane and hexaprismane, the planarity of [6.3]coronane has been postulated.
  • Masao Okubo, Keiko Asao, Hiroyuki Hyakutake
    1987 Volume 60 Issue 10 Pages 3781-3784
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    The 4-, 5-, 6-, and 7-nitro derivatives of benzothiazole condense with ArN(MgBr)2 giving unsym-azoxy and -azo products. The product distribution indicated the mild nature of the reaction, and could be explained in terms of a reduced electron-donating ability of the reagent due to an interaction with thiazolyl group.
  • Osamu Kikuchi, Hideo Togo, Naomichi Furukawa
    1987 Volume 60 Issue 10 Pages 3785-3786
    Published: 1987
    Released: June 27, 2006
    JOURNALS FREE ACCESS
    Ab initio molecular orbital calculations were performed for 2-, 3-, and 4-lithiopyridine monomers, and the molecular and electronic structures of lithiopyridines and their reactivity with electrophiles were examined.
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