bluuebunny/crossref_metadata_2025 huggingface dataset:
Electronic Structure of V2(CO)8(μ-PPh2)2 and Mn2(CO)8(μ-AsPh2)2 by Electron Spin Resonance Study of Their Ion Radicals
Authors: Kawamura Takashi , Enoki Sachio , Hayashida Shigeru , Yonezawa Teijiro
Published: July 2006

The anion radical of V2(CO)8(μ-PPh2)2 and the cation radical of Mn2(CO)8(μ-AsPh2)2 are generated by chemical reduction of the vanadium complex with LiBHEt3 or potassium naphthalenide and by radiochemical oxidation of the manganese complex in frozen Freon mixture, respectively. Their anisotropic ESR spectra show that the V2P2 and the Mn2As2 rhomboids are planar. Their g and hyperfine splitting tensors are analyzed on the basis of a qualitative molecular orbital scheme for metal-metal bonds developed from a hypothesis that metal-ligand interactions are larger than metal-metal interactions. The odd electron orbital of V2(CO)8(μ-PPh2)2−· is assigned to the metal-metal π* MO and the odd electron density on the vanadium d AO is estimated as 0.21. The odd electron of Mn2(CO)8(μ-AsPh2)2+· is concluded to be accomodated in the metal-metal σ* MO and odd electron densities on manganese and arsenic atoms are evaluated as ρ(Mn d)=0.25 and ρ(As p)=0.08 or 0.16, respectively. Order of magnitude estimates of orbital energy differences between metal-metal MO’s are obtained from analyses of g tensors as ε(π*)−ε(σ)\simeq0.4 and ε(π*)−ε(δ)\simeq0.9 eV for the anionic divanadium complex and ε(σ*)−ε(δ*)\simeq1.1 and ε(σ*)−ε(π)\simeq1.4 eV for the cationic dimanganese complex.
The Crystal and Molecular Structure of 3-(1,4-Epoxy-2-hydroxy-2,6,6-trimethylcyclohexyl)-1-methyl-2-propyl p-Nitrobenzoate
Authors: Kitano Yukishige , Kato Tetsuya , Kondo Hisao , Ashida Tamaichi
Published: July 2006

The relative configuration of natural 3,6-epoxy-5-hydroxy-5,6-dihydro-β-ionol, C13H22O3, a principal tobacco constituent, has been established by an X-ray crystal structure analysis of its p-nitrobenzoate, C20H25NO6, as (±)-(1R,2R,5S)-2,5-epoxy-2-[(1E,3S)-3-hydroxy-1-butenyl]-1,3,3-trimethyl-1-cyclohexanol. The derivative crystallizes in space group P\bar1 with a=11.618(1), b=12.373(2), c=7.934(1) Å, α=108.43(1), β=108.89(1), γ=95.95(1)° and Z=2. The crystal structure was solved by the direct phasing method and refined by the blockdiagonal least-squares method to the final R index of 0.073 for 2550 reflections. The hydrogen bondings linking the two molecules placed in pairs around a crystallographic center of symmetry are disordered over two sites in the crystal.
Spectrophotometric Determination of Palladium(II) by Extraction of Its 1-Pyrrolidinecarbodithioate into Molten Naphthalene
Authors: Kumar Avadesh , Hussain M F , Satake Masatada , Puri B K
Published: July 2006

A new spectrophotometric method for the determination of palladium after extraction of its 1-pyrrolidinecarbodithioate into molten naphthalene has been developed. Palladium forms a water-insoluble, thermally stable 1:2 complex with 1-pyrrolidinecarbodithioate which is easily extracted into molten naphthalene in the pH range of 3.0–6.0. At room temperature, solid naphthalene containing the metal-complex is dissolved in chloroform (10 ml). It has an absorption maximum in the range of 336–342 nm. Beer’s law holds in the concentration range of 2.5–90.0 μg of palladium in 10 ml of chloroform solution. The molar absorptivity(1 mol−1 cm−1) and sensitivity (μg/cm2) are found to be 6.4×103 and 0.0166, respectively. Samples containing 30 μg of palladium gives a mean absorbance of 0.18 with a standard deviation of 0.0025. Other factors such as amount of reagent and naphthalene, pH, aqueous phase volume and diverse ions have been examined. The method has been applied to the analysis of some alloys.
Selective Determination of Histamine in Urine by Solvent Extraction with Tetrabromophenolphthalein Ethyl Ester and Atomic Absorption Spectrophotometry
Authors: Sakai Tadao , Ohno Noriko , Wakisaka Takashi , Kidani Yoshinori
Published: July 2006

A simple determination method of histamine in urine by solvent extraction and atomic absorption spectrophotometry has been established. The method is based on the formation of histamine–Cu(II) chelate cation, followed by the extraction of ion-associates with tetrabromophenolphthalein ethyl ester into 1,2-dichloroethane. Histamine in urine can be successfully determined without separation and purification from other histamine derivatives and amines. A linearity is obtained in the concentration range (0.4–4)×10−5 M (1 M=1 mol dm−3) histamine in aqueous solutions. The relative deviation is ca. 1.8%.
Spectrophotometric Determination of Silicic Acid by Flow Injection Analysis
Authors: Yokoyama Takushi , Hirai Yukio , Yoza Norimasa , Tarutani Toshikazu , Ohashi Shigeru
Published: July 2006

Flow injection analysis (FIA) was developed for the spectrophotometric determination of silicic acid based on the formation of a yellow molybdosilicic acid (yellow method) and a heteropoly blue complex (blue method). In the yellow method, silicic acid in the concentration range of 2 to 100 ppm (SiO2) could be determined at a sampling rate of 60 samples/h. The FIA system was modified to determine silicic acid in the presence of orthophosphate. Oxalic acid was used for the decomposition of molybdophosphoric acid. The modified system was employed for the rapid and selective determination of silicic acid in well and river waters. In the blue method, ascorbic acid was used to reduce the yellow molybdosilicic acid to a heteropoly blue complex. Silicic acid in the concentration range of 0.02 to 1.0 ppm (SiO2) could be determined at a sampling rate of 40 samples/h. The FIA system was also modified to determine silicic acid in the presence of orthophosphate. The reducing agent was introduced after molybdophosphoric acid had been completely decomposed by adding oxalic acid. The modified system was employed for the determination of silicic acid in sea water.
Mössbauer Emission Spectroscopic Study of Some Spin Crossover Cobalt(II) Complexes
Authors: Maeda Yonezo , Ohshio Hiroki , Takashima Yoshimasa
Published: July 2006

The Mössbauer emission spectra of [57Co(terpy)2]X2 (X=Cl and ClO4), [57Co(snn)2](ClO4)2, and [57Co(snnme)2](ClO4)2 (terpy=2,2′ : 6′2″-terpyridine, snn=N-(2-pyridylmethylene)-2-(methylthio)aniline, and snnme=N-(6-methyl-2-pyridylmethylene)-2-(methylthio)aniline) were examined. These cobalt complexes show thermally induced spin crossover behavior and the temperature dependence of their magnetic moment varies with the counter anion, although the corresponding iron complexes are in a low-spin state. The high-spin iron(II) species ascribed to a metastable form are observed in the emission spectra of [57Co(terpy)2](ClO4)2·2H2O and [57Co(snnme)2](ClO4)2, and their spectral areas increase with decreasing source temperature. The effective vibrating mass for the iron complex observed in the emission spectra of [57Co(snnme)2](ClO4)2 was calculated from the temperature dependence of the isomer shift value, and was used to distinguish whether the iron complex formed by EC-decay of a cobalt-57 atom is stable or metastable.
Carbon Black as an Electron-transfer Catalyst. The Two-phase Dehydrogenation of Hydrazo Nitriles by an Aqueous Solution of Potassium Hexacyanoferrate(III), Using Carbon Black as the Catalyst
Authors: Tsubokawa Norio , Tareda Naoki , Sone Yasuo
Published: July 2006

The two-phase(aqueous and organic phase) dehydrogenation of hydrazo nitriles by an aqueous solution of potassium hexacyanoferrate(III), using carbon black as the catalyst, was carried out at 40 °C with shaking. In the presence of carbon black, the two-phase dehydrogenation of hydrazo nitriles was accelerated, and the corresponding azo nitriles were obtained in good yields. The catalytic activity of channel blacks was larger than that of furnace blacks. Moreover, the increasing content of phenolic hydroxyl groups tended to increase the catalytic activity of carbon blacks. It became apparent that phenolic hydroxyl groups on the surface of carbon black act as an electron-transfer catalyst in the two-phase dehydrogenation. The reaction scheme was considered to be as follows. In the aqueous phase, phenolic hydroxyl groups on the surface are oxidized by an aqueous solution of K3[Fe(CN)6] to give phenoxyl radicals, and then the carbon black with phenoxyl radicals is transferred into the organic phase, which contains hydrazo nitriles. Subsequently, in the organic phase, the phenoxyl radicals oxidize the hydrazo nitriles to give the corresponding azo nitriles, by which phenolic hydroxyl groups are regenerated. Thus, it was concluded that phenolic hydroxyl groups on the surface are recycled and that carbon black mediates the redox reaction occurring between aqueous and organic phases.
The Dechlorination of Polychlorinated Biphenyls by UV-irradiation. IX. Reactions of Monochlorobiphenyls in a 2-Propanol Solution
Authors: Nishiwaki Tohru , Shinoda Tsutomu , Anda Kinji , Hida Mitsuhiko
Published: July 2006

The multiplicity of the photo-excited state responsible for the dechlorination reaction of monochlorobiphenyls was determined in 2-propanol. Linear Stern-Volmer plots were obtained by the use of 1,3-cyclohexadiene for the dechlorination reactions of 2- and 3-chlorobiphenyl; the slopes were 35.7 and 11.0 dm3 mol−1 respectively. Fluorescence emissions were also quenched, and the quenching constants for 2- and 3-chlorobiphenyls were in accord with the respective values of the slope obtained from the Stern-Volmer plot for the reaction. The reaction of 4-chlorobiphenyl was quenched by cis-1,3-pentadiene, but was accelerated by 1,3-cyclohexadiene. Photosensitized dechlorinations of monochlorobiphenyls took place with several ketones, such as acetone and acetophenonc. These sensitized reactions were, however, very inefficient compared with the reactions in the direct excitations, except in the case of 4-chlorobiphenyl. It was, then, concluded that the dechlorinations of 2- and 3-chlorobiphenyl occurred only from the excited singlet state, while that of 4-chlorobiphenyl took place predominantly from the excited triplet state.
The Isolation and Structures of Novel Neolignans and Neosesquilignans from Heterotropa takaoi M.
Authors: Yamamura Shosuke , Niwa Masatake , Terada Yukimasa , Nonoyama Mikie
Published: July 2006

Several novel neolignans and neosesquilignans represented by heterotropanone and heterotropatrione, respectively, have been isolated from the plant Heterotropa takaoi M. and their structures also been elucidated on the basis of their spectral data closely related to that of asatone. From a biogenetic point of view, furthermore, these neolignans and neosesquilignans were chemically correlated to one another.
Intramolecular Stacking Association of Three Dinucleoside Monophosphates Containing Naturally-occurring 1-Methyladenosine Residue(s): m1ApA, Apm1A, and m1Apm1A
Authors: Takeuchi Yasuhiro , Tazawa Ichiro , Inoue Yasuo
Published: July 2006

Three modified dinucleoside monophosphates containing naturally-occurring 1-methyladenosine residue, m1ApA, Apm1, and m1Apm1A, were prepared. Intramolecular stacking association properties of these dimers were studied quantitatively using two independent methods. Thermal denaturation and acid-base titration experiments reached to the same conclusion that both m1\overset+ApA and Apm1\overset+A were less stacked than ApA. Acidbase titration experiment also showed that the three modified dimers, in their neutral forms, were stacked to almost the same extent as ApA. These results indicate the N-1 methylation of an adenine base does not enhance stacking interaction of dimers, in sharp contrast to the N6 methylation of the same base. UV hypochromicity and CD measurements were also made for the three dimers, and the results were found to be consistent with those of the stacking quotient determination.
A Comparative Study of the Kinetics and Mechanism of Reactions between Copper(I) Iodide and Mercury(II) Halides in Solid State
Authors: Beg Mirza Aijaz , Ahmad Afaq
Published: July 2006

Kinetics and mechanisms of reactions of HgI2, HgBrI, or HgBr2 with CuI were studied in the solid state. Mercury(II) halides react via vapor phase, and reactions proceed through counter diffusion of Cu+ and Hg2+. X-Ray and chemical analyses indicate that powdered Cul gives Cu2HgI4 when mixed with HgI2 and a mixture of Cu2HgI4 and CuBr when mixed with HgBrI. CuI and HgBr2 react differently in different molar ratios. In a 1:2 molar ratio mixture of CuI and HgBr2, a new product CuHgBr3 and HgBrI are obtained. Data for lateral diffusion best fit the equation Xn=kt where X is the thickness of product layer at time t, and n and k are const. Formation of solid solutions among reactant and product phases is also noted.
Electron Transfer Reactions between V(IV) and I(V) Catalyzed by Os(VIII) or Ru(III). A Kinetic Study
Authors: Radhakrishnamurti Patapati Subbu , Janardhana Chelli , Mohanty Gopal Krishna
Published: July 2006

Oxidation of V(IV) by iodate, catalyzed by Os(VIII) or Ru(III) in aq perchloric acid medium, was carried out. The order with respect to oxidant is zero in both the Os(VIII)- and Ru(III)-catalyzed reactions. A unit-order dependence on V(IV) is observed in the case of Os(VIII)-catalyzed reaction and a fractional dependence on V(IV) is noticed in the case of Ru(III)-catalyzed reaction. Both Os(VIII)- and Ru(III)-catalyzed reactions exhibit an inverse unit dependence on acidity. Insensitivity to change in the dielectric constant of medium is observed in both the systems. Effects of salt and ionic strength were studied. A plausible mechanism consistent with the experimental results is postulated, rate laws being derived from the proposed mechanism. The stoichiometry of the reaction has proved to be the same for both the systems.
Synthesis and Characterization of Tin(IV) Thiocarbamates
Authors: Gupta Virendra Kumar , Kanjolia Ravindra Kumar , Gupta Vishnu Deo
Published: July 2006

Tin(IV) thiocarbamates of the types SnX4−n(SOCNR2)n, n-BuSnCl3−n(SOCNEt2)n, and R′2Sn(SOCNEt2)n (where X=Cl, Br, I; R=Me, Et; R′=n-Bu, n-Pr; n=1–4) were synthesized and characterized by elemental analysis and by molar conductance, molecular weight, and IR and NMR measurements.
Photochemical Charging of a Silver Electrode Fixed at a Titanium Dioxide Surface
Authors: Hada Hiroshi , Yonezawa Yoshiro , Momoki Yasuhito
Published: July 2006

A regenerative half cell presented here: TiO2(Ag)–Ag+ can be photochemically charged by irradiation of the TiO2 surface with sunlight. Electrical energy is extracted from it by connection through the load with a suitable half cell which has a more positive electrode potential than Ag–Ag+.
The Formation of Acetylcatechol in the Photochemical Reaction of o-Benzoquinones with Acetaldehyde
Authors: Takuwa Akio , Iwamoto Hidetoshi , Soga Osamu , Maruyama Kazuhiro
Published: July 2006

The irradiation of several alkyl-substituted o-benzoquinones in the presence of acetaldehyde gave the corresponding acetylcatechol and catechol monoacetates via the attack of the acetyl radical on the ground-state quinone molecule. In the reaction of 3,5-di-t-butyl- and 3-t-butyl-5-methyl-o-benzoquinones, the dimer of alkyl-substituted cyclopentadienone, generated by the photodecarbonylation of the quinones, was also obtained.
Reaction of Arenediazonium Salts with Nitriles in the Presence of Sodium Carboxylates. A Convenient Synthesis of Unsymmetrical N-Aryl Acyclic Imides
Authors: Kikukawa Kiyoshi , Kono Kiyoshi , Wada Fumio , Matsuda Tsutomu
Published: July 2006

Reactions of arenediazonium tetrafluoroborates (ArN2BF4), acetonitrile and sodium carboxylates (RCOONa) gave N-acyl acetanilides (ArN(COR)COCH3) in moderate to good yields (Ar=Ph, 2-MeC6H4, 3-MeC6H4, 4-MeC6H4, 2,6-(Me)2C6H3; R=Et, i-Pr, t-Bu, Ph). Acrylonitrile and benzonitrile could be used in the reaction instead of acetonitrile.
Interaction of Amylose with Iodine. II. Kinetic Studies of the Complex Formation by the Temperature-jump Method
Authors: Yamamoto Masako , Sano Takayuki , Harada Shoji , Yasunaga Tatsuya
Published: July 2006

Kinetic studies of the amylose–iodine complex formation for the amylose of degree of the polymerization (DP) of 32 were made using the temperature-jump method. The reciprocal relaxation time increases with increase of the concentration of iodine and decreases with that of amylose. Based on these results, the reaction, H0+3I3−\ightleftharpoonsH3 was proposed as a plausible mechanism for the relaxation phenomenon, where H0 denotes the free helical segment of amylose and H3 the helical segment containing three I3−. The relaxation phenomena were observed for the amyloses of DP 42, 57, and 76, and analyzed by the same mechanism as that proposed in the case of DP 32. The rate constants for the forward and the backward reactions (kf and kb) were determined: the kf value increases with DP of amylose and the kb value decreases. Examination of the relaxation time and the relaxation amplitude suggested that the relaxation phenomenon is not based on the whole process of the amylose–iodine complex formation but on the H3 complex formation reaction which was shown to be the nucleation process.
UV Photoelectron Spectroscopic Investigation and the DV-Xα MO Calculation of Tetrakis(2-methyl-2-propanethiolato)molybdenum(IV)
Authors: Takahashi Masao , Watanabe Iwao , Ikeda Shigero , Kamata Masato , Otsuka Sei
Published: July 2006

Helium(I) ultraviolet photoelectron spectrum is reported for the compound Mo(t-BuS)4. The observed spectrum is interpreted by means of DV-Xα MO calculations on the model compounds Mo(SH)4 and Mo(SMe)4. The UV photoelectron spectrum of Mo(t-BuS)4 exhibits a low ionization potential band (IP=6.43 eV) which corresponds to ionization of mainly Mo4dz2 electron of A1 representation. This molecular orbital has also bonding character between Mo4d and S3d.
Synthesis of A and B Rings Analog of Coleon B
Authors: Matsumoto Takashi , Iyo Koji , Miuchi Shigekazu
Published: July 2006

Catalytic hydrogenation of 19-norabieta-4(18),8,11,13-tetraen-3α-ol over Raney Ni and subsequent dehydration afforded 18-norabieta-2,8,11,13-tetraene, which was converted into 3α-bromo-18-norabieta-8,11,13-trien-2-one (8) via a bromohydrin. Acetalization of 8 with 1,2-ethanediol in the presence of p-toluenesulfonic acid afforded a mixture of 3α-bromo-2,2-ethylenedioxy-18-norabieta-8,11,13-triene (10) and its 3β-bromo isomer (11) in a ratio of ca. 2 : 3. Oxidation of 10 and 11 with chromium trioxide in acetic acid gave the corresponding ketones 12 and 13. The ketone 13 was then converted into a diosphenol derivative, 3β-bromo-2,2-ethylenedioxy-6-hydroxy-18-norabieta-5,8,11,13-tetraen-7-one (14), by treatment with oxygen in the presence of potassium t-butoxide. Hydrolysis of 14 with dilute hydrochloric acid followed by dehydrobromination afforded the desired analog, 6-hydroxy-19-norabieta-3,5,8,11,13-pentaene-2,7-dione. A related A/B ring oxygenated compound, 19-norabieta-3,5,8,11,13-pentaene-2,7-dione was also synthesized from 12 and 13  via the corresponding 6α-bromo derivatives.
Synthesis of 11,14-Diacetoxy-13-(acetoxymethyl)podocarpa-8,11,13-triene. Correction of Proposed Structure for Premnolal
Authors: Matsumoto Takashi , Imai Sachihiko , Yuki Shuhei
Published: July 2006

Oxidation of 11-acetoxyabieta-8,11,13-triene, derived from methyl 11-methoxyabieta-8,11,13-trien-18-oate, with chromium trioxide afforded 11,15-diacetoxyabieta-8,11,13-trien-7-one and 11-acetoxy-13-acetylpodocarpa-8,11,13-trien-7-one (11) in a ratio of ca. 2 : 1. The acetyl compound 11 was converted into a quinone, 13-(hydroxymethyl)podocarpa-8,12-diene-11,14-dione (18), by a series of reactions : iodoform reaction, esterification, acetylation, sodium borohydride reduction, dehydration, catalytic hydrogenation, lithium aluminium hydride reduction, and oxidation with Fremy’s salt. Reductive acetylation of 18 produced 11,14-diacetoxy-13-(acetoxymethyl)-podocarpa-8,11,13-triene (2). The 1H NMR spectrum of 2 was different from that of 15-acetoxypremnol diacetate which was prepared from natural premnolal. Based on this fact a corrected structure of premnolal is proposed.
EXAFS Spectroscopy of Some Iron(III) Compounds by Use of Dispersive-type In-laboratory X-Ray Spectrometer
Authors: Nomura Masaharu , Asakura Kiyotaka , Kaminaga Ukyo , Matsushita Tadashi , Kohra Kazutake , Kuroda Haruo
Published: July 2006

A dispersive-type in-laboratory EXAFS spectrometer was constructed by combining a transmission-type dispersing crystal and a position-sensitive proportional counter. FeK absorption spectra were measured by use of this apparatus on FeCl3·6H2O, Fe(ClO4)3·6H2O and anhydrous FeCl3. Discussion is given on the results obtained from the analyses of observed EXAFS data concerning the structure around Fe ions in these compounds. AsI3-like structure is proposed for anhydrous FeCl3.
Photoelectron Angular Distribution Study of Some Isoxazoles Combined with Perturbation Theoretic Approach
Authors: Kobayashi Tsunetoshi , Kubota Tanekazu , Ezumi Kiyoshi , Utsunomiya Chikatoshi
Published: July 2006

Photoelectron spectra of isoxazole, 5-methylisoxazole, and 3,5-dimethylisoxazole were studied by the technique of photoelectron angular distribution measurements combined with a first order perturbation theoretic approach. Photoelectron spectra of oxazole, 4-methyloxazole, furan, and 2-methylfuran, which are closely related to isoxazole, were also discussed at the same time for the sake of comparison. The first three bands of the isoxazoles were assigned to the π, π, and n bands from the top, respectively, while those of the oxazoles were identified as the π, n, and π bands from the top.
Studies of the Cobalt(III) Complexes of 8-Amino-3,6-diazaoctanate Ion. III. Preparations and Some Properties of Complexes with Chloro, Nitro, or Aqua Ligands
Authors: Watanabe Kiyokatsu
Published: July 2006

The following new cobalt(III) complexes containing the 8-amino-3,6-diazaoctanate ion (adao) have been prepared: α-[Co(adao)Cl2], two isomers of β-mer(N)-[Co(adao)Cl2], β-fac(N)-[Co(adao)Cl2], α-[Co(adao)(NO2)2], two isomers of β-mer(N)-[Co(adao)(NO2)2], α-[Co(adao)(H2O)2](ClO4)2, and β-mer(N)-[Co(adao)(H2O)2](ClO4)2. The geometrical structures have been determined on the basis of the electronic spectra, the proton NMR spectra, and the deductions from their derivation processes.
Binuclear Metal Complexes. XLII. Manganese(IV) Complexes Synthesized by Oxidation of Binuclear Manganese(II) Complexes of 2-(Salicylideneamino)phenols with Tetrachloro-o-benzoquinone
Authors: Okawa Hisashi , Nakamura Masaaki , Kida Sigeo
Published: July 2006

Manganese(IV) complexes Mn(R-R′-sap)2, where H2(R-R′-sap) denotes 2-(salicylideneamino)phenols with the substituent R on the salicylaldehyde ring and the R′ on the o-aminophenol ring, were prepared by the oxidation of binuclear manganese(II) complexes Mn2(R-R′-sap)2 with tetrachloro-o-benzoquinone (TCOQ). The complexes showed magnetic moments corresponding to three unpaired electrons and strong absorptions in the region 15–20×103 cm−1 attributable to CT transitions. Cyclic voltammograms of Mn(R-R′-sap)2 showed two redox waves which can be interpreted in terms of a two-step reaction, Mn(IV)\ightleftharpoonsMn(III)\ightleftharpoonsMn(II). Both redox potentials of the first and the second processes depend on the substituents R and R′, and there is a good correlation between the redox potentials and Hammett’s σ-values of R and R′ to the phenolic oxygen. Mn2(R-R′-sap)2 reacts with TCOQ to give a binuclear manganese(III) complex Mn2(R-R′-sap)2(tcoq), which decomposes in the presence of water forming Mn(R-R′-sap)2.
Binuclear Metal Complexes. XLIII. Magnetic, Spectroscopic, and Electrochemical Studies on Hetero-metal Binuclear Complexes of N,N′-Bis(3-carboxysalicylidene)-1,1-dibenzylethylenediamine
Authors: Kanda Wakako , Nakamura Masaaki , Okawa Hisashi , Kida Sigeo
Published: July 2006

Copper(II)–M(II) and copper(II)–iron(III) hetero-metal binuclear complexes of N,N′-bis(3-carboxysalicylidene)-1,1-dibenzylethylenediamine (H4fsadb), CuM(fsadb)·nH2O (M=Co, Ni, Cu, Zn, Mg, Ca, Ba) and CuFe(fsadb)Cl·1.5H2O, have been prepared and characterized. Cryomagnetic measurements (78–300 K) revealed that an antiferromagnetic spin-exchange interaction operates between the metal ions in the cases CuM(fsadb)·nH2O (M=Co, Ni, Cu) and CuFe(fsadb)Cl·1.5H2O, exchange integrals being evaluated on the basis of the Heisenberg model. Ligand field bands due to the copper(II) ion bound at the N2O2-site of CuM(fsadb)·nH2O (M=Co, Ni, Cu, Zn, Mg) and CuFe(fsadb)Cl·1.5H2O are in the range 1.9×103–21.4×103 cm−1, while in the cases of CuCa(fsadb)·4H2O and CuBa(fsadb)·3.5H2O the frequencies of the bands are close to that (17.8×103 cm−1) of the mononuclear complex Cu(H2fsadb)·H2O. This spectral feature has been explained in terms of the configuration of the second metal ion adjacent to the copper(II) ion: trans-octahedral in the cases of small metal ions (Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Mg(II)) and presumably cis-octahedral in the cases of large metal ions (Ca(II), Ba(II)). Copper(II/I) redox potentials of the hetero-metal complexes are much low compared with that of Cu(H2fsadb)·H2O. This shift has been discussed in terms of the electronic effect of the carboxylate group and the covalency in the bonding between the bridging phenolic oxygen and the second metal ion.
Electron Transfer between Hexacyanoferrate(III) and Thiosulfate. Kinetic Studies in the trans-Dihydroxotetraoxoosmate(VIII) Oxidation and the trans-Dihydroxotetraoxoosmate(VIII)-catalyzed Hexacyanoferrate(III) Oxidation of Thiosulfate in Aqueous Alkaline Media
Authors: Panda Rama Krushna , Neogi Gautam , Ramaswamy Dorai
Published: July 2006

Kinetics of oxidation of thiosulfate to tetrathionate by trans-dihydroxotetraoxoosmate(VIII) (Os(VIII)) and by hexacyanoferrate(III) in the catalytic presence of Os(VIII) have been studied in aqueous alkaline media. The observed pseudo-first-order rate constants for disappearance of Os(VIII) in the Os(VIII)–S2O32− system (kobsd), and those for disappearance of hexacyanoferrate(III) in the Os(VIII)-catalysed Fe(CN)63−–S2O32− system (kcat) conform, respectively, to Eqs. A and B:

k obsd=k3KOsK2[S2O32−](1+KOs[OH−]+KOsK2[S2O32−])−1, (A)

k cat=k6KOsK2[Os(VIII)][OH−][S2O32−](1+KOsK2[S2O32−])−1, (B)

where KOs is the stability constant of trans-dihydroxotetraoxoosmate(VIII) in aqueous alkaline media, K2 and k3 are the formation and decomposition constant of the intermediate complex 1, and k6 refers to the rate constant of electron-transfer from 1 to hexacyanoferrate(III). The values of KOs and K2, as obtained from spectrophotometric titrations and stopped-flow spectrophotometry, respectively, are 19.5±3 dm3 mol−1 and 5.58±0.13; the computed values from kinetic data of KOs, K2, and k3 at 30 °C and μ=0.32 mol dm−3, and that of k6 at 35 °C and μ=0.32 mol dm−3 are 22.5±2 dm3 mol−1, 6.12±0.5, (3.32±0.3)×10−1 dm3 mol−1s−1, and (3.31±0.3)×10−2 dm6 mol−2s−1, respectively. Possible mechanisms for electron-transfer are discussed in terms of an initial equilibrium interaction between Os(VIII) and S2O32− forming an intermediate complex [OsO4(OH)(S2O3)3−] (1) followed by (a) a rate-determining decomposition of 1, with concomitant electron-transfer, in the Os(VIII)–S2O32− system, and (b) a rate-determining outersphere electron-transfer from 1 to hexacyanoferrate(III) in the Os(VIII)-catalyzed Fe(CN)63−–S2O32− system.
The Conversion of Benzyl Alcohols into Phenylacetic Acid Derivatives by Cobalt Carbonyl Catalyzed Carbonylation
Authors: Imamoto Tsuneo , Kusumoto Tetsuo , Yokoyama Masataka
Published: July 2006

Benzyl alcohols were converted into the corresponding one carbon-homologated amides or esters in one pot by cobalt carbonyl catalyzed carbonylation in the presence of ethyl polyphosphate (PPE) and sodium iodide.
Determination of Circular Dichroism in Multiple Scattering Systems
Authors: Taniguchi Yutaka , Shimura Yoichi
Published: July 2006

In a thick suspension circular dichroism cannot be directly determined by the Grosjean-Legrand type CD instrument, because Lambert’s law does not hold in it. The transfer of light intensity is discussed when polarized light is incident on a plane-parallel scattering medium containing randomly oriented, optically active particles. This problem is analyzed based on a two-beam radiative transfer model. We provide a method to determine the molar CD in a multiple scattering system. The measurements of ellipticity and transmittance with conventional instruments is served for our method by using a plate of opal glass. The molar CD is determined in Nujol mulls of Λ-[Co(en)3]Br3·H2O and [Co(NH3)6](d-tart)1.5·5H2O. The results are reproducible and reliable.
Synthetic Approach toward Antibiotic Tunicamycins. II.
Authors: Fukuda Yoshimasa , Kitasato Hiderou , Sasai Hiroaki , Suami Tetsuo
Published: July 2006

Some higher-carbon carbohydrates, dodecose derivatives, have been synthesized by means of the basecatalyzed addition of nitro sugar to sugar aldehyde. The addition reaction of 6,7-dideoxy-1,2:3,4-di-O-isopropylidene-7-nitro-α-d-galacto-heptopyranose to 2,3:4,5-di-O-isopropylidene-d-arabinose yielded three isomeric dodecose derivatives, and their configurations have been studied. The nitro dodecose derivatives were converted into the corresponding hydroxy and acetoxy derivatives.
The Extraction of Bivalent Transition Metals from Aqueous Chloride Solutions by Long-chain Alkyl Quaternary Ammonium Carboxylates
Authors: Sato Taichi , Yamamoto Masahiro
Published: July 2006

The extraction of bivalent manganese, cobalt, nickel, and copper from aqueous chloride solutions by longchain alkyl quaternary ammonium carboxylates, prepared by combination of trioctylmethylammonium chloride (R3R′NCl) and carboxylic (octanoic, decanoic, and lauric) acids (R″COOH) in benzene, has been investigated under different conditions. The organic phases are examined by spectrophotometry and infrared spectral measurement. The mechanism of the extraction is discussed on the basis of the results obtained. The extraction efficiency follows the order Cu>Co\simeqNi>Mn, and the extraction process is expressed as M2+(aq)+2Cl−(aq)+3R3R′NR″COO(org)\ightleftarrows(R3R′N)[M(R″COO)3](org)+2R3R′NCl(org), in which M=Mn, Co, Ni, and Cu. The extracted species of bivalent manganese, cobalt, nickel, and copper exist as the complex (R3R′N)[M(R″COO)3] in an octahedral arrangement.
Properties of Magnesium Oxides Prepared from Various Salts and Their Catalytic Activity in 1-Butene Isomerization
Authors: Matsuda Tsuneo , Tanabe Jun , Hayashi Nobuatsu , Sasaki Yoh , Miura Hiroshi , Sugiyama Kazuo
Published: July 2006

The basicity, one-electron donor property, and surface area were examined on the magnesium oxide catalysts prepared from six different kinds of magnesium salts. Magnesium oxide prepared from magnesium nitrate, oxalate, and acetate exhibited strong basicity and relatively large surface area and, on the other hand, MgO prepared from magnesium chloride, carbonate and sulfate had relatively weak basicity and small surface area. Number of one-electron donor centers hardly changed in the variety of magnesium oxides, except the one prepared from magnesium chloride. Magnesium oxide prepared from chloride showed both the lowest basicity with less strength than H−=15.0 and surface area in the six kinds of catalysts. In order to examine the influence of remaining anions in MgO a variety of catalysts were prepared by the addition of ammonium chloride, sulfate, and carbonate, respectively in MgO prepared from the nitrate. Ammonium chloride brought the greatest influence on the basicity, one-electron donor property, and surface area. Thus the remaining chloride ion greatly affected such properties as cited above. Sodium nitrite which decomposes at higher temperature than 320 °C was added to the magnesium oxides for the examination of the effect of the sodium cation. The amount of the basicity with a moderate strength (H−=15.0–22.3) increased by the addition of NaNO2. This was ascribed to the formation of the moderate strength of basicity by the interaction of Na2O, one of the decomposed products of NaNO2 and MgO. Isomerization of 1-butene was carried out on the six kinds of catalysts at 30 °C. The magnesium oxides prepared from nitrate, oxalate, and acetate salts (group A) exhibited isomerization activity and the ones from chloride, sulfate, and carbonate (group B) did not entirely. The isomerization activity could be correlated with the stronger basicity than H−=22.3. Temperature pregrammed desorption curves of acetic acid adsorbed on the catalysts indicated two peaks at around 350 and 420 °C in group A catalysts and only one at 350 °C in group B. The desorbed peak at around 420 °C was assigned to the adsorbed acetic acid on the stronger basic sites than H−=22.3.
The Absorption Spectra of Monolayers of Fluorescent Probes and the Orientations of Their Chromophores
Authors: Matsuki Kazunori , Fukutome Hideo
Published: July 2006

The UV absorption spectra of monolayers of 12-(9-anthrylcarbonyloxy)octadecanoic acid (12-AS), 2-(9-anthrylcarbonyloxy)hexadecanoic acid (2-AP), and 2-octadecylamino-6-naphthalenesulfonic acid (ONS) were measured at normal incidence and the polarized spectra at 45° incidence. New peaks which were absent in the spectra of their solutions were observed in the polarized spectra at 45° incidence. The orientation of their chromophores in the monolayers were investigated by means of the dichroic ratios obtained from their polarized spectra. These monolayers were found to consist of H-aggregates where chromophores are oriented nearly perpendicularly to the monolayer plane and molecules in a monomer-like state where the chromophores are rather randomly oriented. The molecular axes of 12-AS, 2-AP, and ONS were found to be oriented uniaxially against the normals of their monolayer planes in the ranges 0–7°, 0–21°, and 0–34°, respectively.
Isotope Effect on the Emission Cross Section and Translational Energy of Excited Hydrogen Atoms Produced in Electron-Hydrogen Chloride Collisions
Authors: Higo Morihide , Kamata Satsuo , Ogawa Teiichiro
Published: July 2006

The Balmer-α, β, γ lines of the excited hydrogen atoms (n=3, 4, 5) produced in e-HCl and DCl collisions have been measured in the energy range of 30–300 eV. The average translational energies of H* and D* are 4–5 eV at higher electron energies and 2–2.5 eV at lower electron energies; no appreciable isotope effect is found for the translational energy. The relative emission cross section of D* and H* shows an isotope effect and this effect is larger in the lower electron energy range; σD⁄σH’s are 0.74 for n=3, 0.71 for n=4 and 0.78 for n=5 at 30 eV. These results show that there are two groups of the excited hydrogen atoms and their relative cross sections vary with the electron energy. The existence of the isotope effect indicates a competing decay process in the repulsive excited states of HCl.
Synthetic Control by Internal Interaction. The Intramolecular Diels-Alder Reactions of Furan Derivatives and α, β-Unsaturated Amides
Authors: Takebayashi Toyonori , Iwasawa Nobuharu , Mukaiyama Teruaki
Published: July 2006

An efficient method for the acceleration of the intramolecular Diels-Alder reaction was established utilizing the internal interaction—the internal hydrogen bonding and the internal coordination of a magnesium salt. The intramolecular Diels-Alder reaction between nitrofuran derivatives and various acrylic acid derivatives give good yields of the cycloadducts when internal hydrogen bonding is present. When cyclic α,β-unsaturated amides are employed as dienophile, the corresponding cycloadducts are obtained in high yield utilizing internal coordination of a magnesium salt.
Studies of Bitter Peptides from Casein Hydrolyzate. II. Syntheses of Bitter Peptide Fragments and Analogs of BPIa (Arg–Gly–Pro–Pro–Phe–Ile–Val) from Casein Hydrolyzate
Authors: Otagiri Ken , Miyake Ichizo , Ishibashi Norio , Fukui Hiroshi , Kanehisa Hidenori , Okai Hideo
Published: July 2006

In order to investigate the relationship between bitterness and chemical structure of BPIa, eleven kinds of fragments and analogs of BPIa were synthesized. des–Gly2–BPIa and des-Pro4-BPIa exhibited extremely bitter taste. However, the pentapeptide (Arg–Gly–Pro–Pro–Phe) of BPIa possessed weak bitterness. The bitterness exhibition of BPIa probably derived from the spatial structure of its molecule.
Synthesis and Enzymatic Carboxylation of a Biotin-containing Peptide Representing the Coenzyme Binding Site of E. coli Acetyl–CoA Carboxylase
Authors: Kondo Hiroki , Uno Shingo , Moriuchi Fumio , Sunamoto Junzo , Ogushi Susumu , Tsuru Daisuke
Published: July 2006

A biotin-containing pentapeptide Boc–Glu–Ala–Met–Bct–Met (1) that corresponds to the coenzyme binding site of E. coli acetyl–CoA carboxylase has been prepared. Peptide 1 as well as free biotin served as a substrate for the carboxylation reaction catalyzed by the biotin carboxylase subunit dimer of E. coli acetyl–CoA carboxylase. The Michaelis constant, Km, and the maximum velocity, Vmax, for 1 were 18 mM and 2.8 μM min−1 (1 M=1 mol dm−3), respectively. The corresponding values for biotin were 214 mM and 28 μM min−1. Thus, the overall reactivity (Vmax⁄Km) of peptide 1 exceeded that of biotin by 20%.
ESR Studies of Unstable Six-coordinated Cobalt(II) Complexes Produced by γ-Radiolysis of Glassy Solutions at 77 K
Authors: Hoshino Mikio , Konishi Shiro , Nakajima Masao , Imamura Masashi
Published: July 2006

ESR spectra of γ-irradiated glassy solutions of cobalt(II) chelates of N,N′-bis(1-methyl-3-oxobutylidene)ethylenediamine (acacen) having two NH3 in the axial positions at 77 K show the formation of a metastable cobalt(II) complex in which two NH3 are forced to be confined in the axial positions.
Syntheses and Characterization of Lanthanoid(III) Propoxyacetate
Authors: Kondo Satoshi , Nagai Kiyofumi , Ouchi Akira
Published: July 2006

New lanthanoid(III) complexes with the formula of ML3·H2O, where M=La, Ce, Pr, Nd, Eu, Dy, or Er, and HL=propoxyacetic acid, have been synthesized; they are isostructural with each other. From the shift direction of the 1H-NMR peaks of L− in an aqueous solution upon adding Eu(III) or Pr(III) salt, the ligand is likely to be coordinated to the metal by both the ether and carboxyl oxygen atoms.
Preparation of Alkanesulfenamides by Selective Elimination of t-Butyl Group in S-Alkyl-S-t-butylsulfilimines
Authors: Yamamoto Tamotsu , Kakimoto Masa-aki , Maejima Takeshi , Okawara Makoto
Published: July 2006

N-Tosylalkanesulfenamides have been prepared via the reactions of alkyl halides with 2-methyl-2-pro-panethiolate followed by S-imination with chloramine T and the thermolysis. This method comprises the use of selective elimination of t-butyl group in S-alkyl-S-t-butylsulfilimines.
Fluorescence Spectrum and Its Intensity of Europium Tris(ethyl sulfate) Enneahydrate
Authors: Ohoka Tomoyuki , Kato Yoshifumi
Published: July 2006

The polarized fluorescence spectrum of the europium tris(ethyl sulfate) enneahydrate crystal was measured at 95 K by using excitation lines of an Ar+ laser. The multipole character of transitions and the energies and crystal quantum numbers for the crystal field components of the 7FJ(J=0, 1,···,6) and 5D0.1 terms were determined from the spectral analysis. It was ascertained that most of the transitions were due to forced electric dipole transitions but some of them due to magnetic dipole transitions, in which nine strong lines appeared as magnetic dipole radiations satisfying the selection rule for ion levels, while three weak lines were magnetic dipole radiations forbidden in ions. The relative intensities of both the forbidden electric dipole transitions and the magnetic dipole transitions were calculated by the crystal field wavefunctions obtained to reproduce the experimental data. From the comparison of the calculated intensities with the observed ones, the ratio of the populations of the 5D0 term to the 5D1 term in fluorescent process was estimated to be about 20, although the 5D0 term was 1750 cm−1 lower than the 5D1 term. The result suggested that the configuration mixing due to g-orbitals was significant to allow electric dipole transitions.
Excimer Fluorescence of 1,2-Di(9-anthryl)ethane, 1,3-Di(9-anthryl)propane, and 9,9′-Bianthryl at High Pressures
Authors: Hara Kimihiko , Katou Yoshikazu , Osugi Jiro
Published: July 2006

Fluorescence spectra of 1,2-di(9-anthryl)ethane (1), 1,3-di(9-anthryl)propane (2), and 9,9′-bianthryl (3) have been studied at high pressures up to 50 kbar both in crystalline state and in PMMA matrix. In the case of 1 and 2 in crystalline state, the excimer emissions appear reversibly at high pressures accompanied by the reversible red shifts. While in PMMA the fluorescence spectra assigned as locally excited state are observed, whose peak shifts are quite analogous to that of anthracene in the same matrix. As for 3, a new band also appears at high pressure which is similar to the intramolecular charge-transfer band. Possible interpretations of the pressure effects are discussed.
Kinetics of the Formation of the Intermediate Complex in the Aromatic Nucleophilic Substitution of Methyl 4-Methoxy-3,5-dinitrobenzoate with Piperidine in Dimethyl Sulfoxide
Authors: Hasegawa Yoshinori
Published: July 2006

The intermediate complex in the aromatic nucleophilic substitution of methyl 4-methoxy-3,5-dinitrobenzoate with piperidine in dimethyl sulfoxide was confirmed by visible absorption spectroscopy. Kinetics of the formation of the intermediate were studied by a stopped-flow spectrophotometer, and rate and equilibrium constants were determined. The observable intermediate (Z−) was the conjugate base of the initial zwitterionic complex (ZH). Proton transfer between ZH and Z− was rate limiting and the intermediate formation was base catalyzed.
Temperature Programmed Reduction of Copper–Silica Catalysts Prepared by Ion Exchange Method
Authors: Shimokawabe Masahide , Takezawa Nobutsune , Kobayashi Haruo
Published: July 2006

Temperature programmed reduction (TPR) has been used to study copper–silica catalysts which were prepared by ion exchange method and the effects of preparation of catalysts upon their reducibilities were elucidated. Three peaks appeared with maxima at 265–300 °C (α), 400 °C (β), and 650–800 °C (γ) over the catalysts calcined at 500 °C. Highly dispersed cupric oxide clusters were reduced to metallic copper, giving α peak. Isolated copper(II) ions which were strongly interacted with silica surface were reduced stepwise to metallic copper through copper(I) ion species, giving α and γ peaks. However, isolated copper(II) ions which were weakly interacted with the support gave α and β peaks. When the catalysts were precalcined above 800 °C, the fourth peak (α′) appeared at 330–350 °C and α, β, and γ peaks diminished. This was assigned to the reduction of bulk CuO which was crystallized from species described above. The reducibility of copper–silica catalyst was found to depend strongly upon the conditions of preparation.
Kinetics of the Precipitation of Human Fibrinogen by ZnCl2 and CuCl2
Authors: Kishi Takaaki , Maeda Hiroshi , Ikeda Shoichi
Published: July 2006

Kinetics of the precipitation of human fibrinogen by the addition of ZnCl2 was followed by the turbidity at 350 or 500 nm. Fast or slow precipitation occurred depending on whether the metal concentration (CM) was higher or lower than its critical value. In fast precipitations, the turbidity reached the stationary value within about 30 min. From the stationary values of the turbidity the critical concentration could be determined. A sigmoidal increase of the turbidity was often observed at low protein concentrations (CP); the lag time decreased with both CM and CP. At the final stage of the precipitation, the turbidity reached the stationary value exponentially; the characteristic time constant was almost independent of both CM and CP. These kinetic behaviors were consistent with the gelation model proposed to the present precipitation. When CuCl2 was used in place of ZnCl2, similar kinetic behaviors were obtained in many respects, suggesting the similar mechanism of precipitation for both ZnCl2 and CuCl2. Changes from slow to fast precipitation were observed when ionic strength was lowered.
Mono-complex Formation Kinetics of 2-Thenoyltrifluoroacetone with Nickel(II) and Copper(II) Ions in Aqueous Solution
Authors: Ando Isao , Yoshizumi Kiyomi , Ito Kazuhisa , Ujimoto Kikujiro , Kurihara Hirondo
Published: July 2006

The mono-complex formation of 2-thenoyltrifluoroacetone (HTTA) with nickel(II) and copper(II) ions was studied in aqueous solution at 25.0 °C and an ionic strength of 0.20 mol dm−3 by means of a stopped-flow method. The rate-[H+] profiles for the formation of these mono-complexes revealed that the rate-determining step of the complex formation interchanges depending upon hydrogen-ion concentration, as in the case of the Ni(II)–bpy complex. The rate constants of the mono-complex formation with TTA−, kf, and that with HTTA, kfh, were determined from the rate-[H+] profile in the region of the high hydrogen-ion concentration, where the pseudo-equilibrium of acid dissociation of the ligand was maintained during the complex formation; kf=(9.2±3.0)×102, kfh=(1.3±0.3)×10−1 mol−1 dm3 s−1 for the Ni(II)–TTA complex and kf=(2.0±1.2)×103, kfh=(5.0±0.9)×10−1 mol−1 dm3 s−1 for the Cu(II)–TTA complex. The deprotonation-rate constants of HTTA could be evaluated from the apparent rate constants of the complex formation in low hydrogen-ion concentration. The values thus obtained agreed well with that determined independently by a pH jump method.
Inversion of the Retention Volume Order of Enantiomers Caused by the Concentration of Eluent
Authors: Sakaguchi Ushio , Yamamoto Ippei , Izumoto Shinji , Yoneda Hayami
Published: July 2006

The retention volumes of enantiomers of several complex anions on the IEX 220 anion-exchange resin, when eluted by an aqueous solution of Δ-[Co(en)3]3+, Δ-[Co(sep)]3+, or Δ-[Co(l-chxn)3]3+, have been measured as a function of the eluent concentration, where en=ethylenediamine, sep=1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]eicosane, and l-chxn=(−)-trans-1,2-cyclohexanediamine. The order of retention volumes of enantiomers of some complex anions has been found to be inverted by the concentration of the eluents. The mechanism of the inversion has been discussed.
Synthetic Studies on Methyl α-Trioxacarcinoside B
Authors: Suami Tetsuo , Nakamura Katsumi , Hara Tamio
Published: July 2006

Trioxacarcinose B is a unique carbohydrate which has been discovered in antibiotic trioxacarcin A as a component. As a step of total synthesis of the antibiotic, methyl α-trioxacarcinoside B has been synthesized from methyl 2,3-anhydro-6-deoxy-α-l-allo-hexopyranoside by a 7 steps reaction in a yield of 4.3%. The product has been identified by comparison with the authentic sample which was prepared by methanolysis of the antibiotic.
Synthesis of Potential Antineoplastic Anthracenedione Derivatives. I. Sugar Derivatives
Authors: Nakamura Katsumi , Asai Tomoyuki , Hara Tamio , Minorikawa Naoki , Suami Tetsuo
Published: July 2006

Seven 1-O-glycosyl derivatives of 4-[2-(2-hydroxyethylamino)ethylamino]-9,10-anthracenedione have been prepared as potential antineoplastic agents.
The Identification of 3-Amino-9H-pyrido[3,4-b]indole Derivatives in l-Tryptophan Pyrolysates
Authors: Tada Masao , Saeki Hisaaki , Oikawa Atsushi
Published: July 2006

The compounds, 3-amino-9H-pyrido[3,4-b]indole and 3-amino-1-methyl-9H-pyrido[3,4-b]indole, which are effectors in induction of sister chromatid exchanges in human cells, were isolated from pyrolysis products of l-tryptophan and characterized by HPLC and UV techniques.
The Reaction of Benzonitrile Oxides with S,S-Dimethyl-N-(2,4,6-trihalophenyl)sulfimides. The Formation of Benzoxazole Derivatives
Authors: Shiraishi Shinsaku , Hayakawa Tohru , Shigemoto Tadashi
Published: July 2006

The reactions of nitrile oxides with S,S-dimethyl-N-(2,4,6-trihalophenyl)sulfimides gave unusual products, which structure was determined to be 2-aryl-4,6-dihalobenzoxazoles from their elementary analyses and spectral data. While the reactions with S,S-dimethyl-N-(2-bromophenyl)- or S,S-dimethyl-N-(2,4-dibromophenyl)sulfimide gave 1,2,4-benzoxadiazine derivatives. A plausible reaction mechanism for the unusual formation of benzoxazoles was proposed.