bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pentamethylnitrosobenzene as a Spin-trapping Agent
Authors: Doba Takahisa , Ichikawa Tsuneki , Yoshida Hiroshi 
Published: July 2006

Abstract
Pentamethylnitrosobenzene synthesized readily from pentamethylbenzene was studied for utilization in a spin-trapping technique. In a benzene solution it forms a dimer with a dissociation constant of 105.26exp(−50⁄RT) in units of kJ/mol. It traps the t-butyl radical with the trapping rate constant of 1.4×108 mol−1 dm3 s−1 at 299 K. It is thus an efficient spin-trapping agent, even though only a fraction of it is reactive with the short-lived free radicals because the equilibrium lies more on the side of the dimeric form. Electron spin resonance parameters were determined for the spin-adduct radicals derived from alkyl, alkoxyl, and phenyl radicals with this trapping agent. These free radicals were found to attach exclusively to the nitrogen atom of the nitroso compound.
Crystal Structure and Electrical Conductivity of Tetrathiafulvalene Thiocyanate (TTF)(SCN)0.57
Authors: Kobayashi Hayao , Kobayashi Keiji 
Published: July 2006

Abstract
The organic conductor, (TTF) (SCN)0.57, is a quasi-one-dimensional non-stoichiometric compound, which crystallizes in a tetragonal system having a P42/mnm space group. The lattice constants are a=11.154 (3) and c=3.607 (2) Å. TTF molecules form segregate eclipsed stacks with thiocyanate ions occupying the channels between the stacks. The intermolecular distance between adjacent TTF molecules is 3.607 Å. The room-temperature electrical conductivity is 85–310 (Ω cm)−1. A series of resistance jumps are observed in the temperature-dependent resistivity curves.
Kinetic Studies on Double Relaxation of Surfactant Solutions Using a Capillary Wave Method
Authors: Sasaki Minoru , Yasunaga Tatsuya , Satake Shigemi , Ashida Minoru 
Published: July 2006

Abstract
The frequency dependence of the damping coefficient of a capillary wave was measured in decylamine hydrochloride solutions. The observed relaxations were well expressed by the double-relaxation equations. From the concentration dependence of the relaxation parameters obtained, the relaxations at low and high frequencies were attributed to the adsorption-desorption and ion-pair formation reactions on the surface, respectively. Furthermore, the adsorption rate constants are related to the hydrophobic and hydrophilic properties of the surfactants.
Synthetic Photochemistry. VII. The Addition Reaction of Acenaphthenequinone and 1,2-Naphthoquinone to Cycloheptatriene
Authors: Takeshita Hitoshi , Mori Akira , Funakura Mitsuru , Mametsuka Hiroaki 
Published: July 2006

Abstract
The photoaddition reaction of acenaphthenequinone and 1,2-naphthoquinone to cycloheptatriene was investigated. In contrast to acyclic α-diketones, various cycloadducts were formed from both quinones; the former giving the (2+2)π-, and (2+6)π-cycloadducts together with the ene-product, and the latter the (2+6)π-, (4+2)π-, and (4+4)π-cycloadducts.
Kinetic Studies of Spin-trapping Reactions. I. The Trapping of the t-Butyl Radical Generated by the Photodissociation of 2-Methyl-2-nitrosopropane by Several Spin-trapping Agents
Authors: Doba Takahisa , Ichikawa Tsuneki , Yoshida Hiroshi 
Published: July 2006

Abstract
The photochemical reaction of 2-methyl-2-nitrosopropane (a spin-trapping agent) in benzene was studied at 299 K by monitoring the optical absorption intensity of the spin-trapping agent and the ESR signal intensity of the spin-adduct radical (di-t-butyl nitroxide). The observed kinetic feature was interpreted in terms of three elementary processes; the photodissociation of the spin-trapping agent giving a t-butyl radical, the spin trapping of the t-butyl radical by the trapping agent giving the spin adduct radical, and the reaction of the spin-adduct radical with the t-butyl radical giving diamagnetic products. The rate constant of the last process was found to be 10 times as large as that of the spin-trapping process, which was determined to be 3.3×106 mol−1 dm3 s−1 based on the reported rate constant for the scavenging of the t-butyl radical by tributylstannane. The relative spin-trapping rate constants toward the t-butyl radical were also determined to be 0.07, 1.0, 41, 63, and much higher than 50 for 2,4,6-tri-t-butylnitrosobenzene, 2-methyl-2-nitrosopropane, pentamethylnitrosobenzene, nitrosodurene and nitrosobenzene, respectively. C-phenyl-N-t-butylnitrone was found to be much less reactive by a factor of less than 0.003.
Absolute Rate Constants for Hydrogen Abstraction from Some Aromatic Hydrocarbons by p-Chlorophenylthiyl Radical
Authors: Miyashita Tokuji , Iino Masashi , Matsuda Minoru 
Published: July 2006

Abstract
The absolute rate constants for hydrogen abstraction from cumene, p-cymene, and tetralin by p-chlorophenylthiyl radical have been determined by means of flashphotolysis and kinetic absorption spectrophotometry. The results are discussed in comparison with those reported for other types of free radicals.
The Crystal and Molecular Structure of Dichloro [N, N-dimethyl-α-methyl-o-(butylphenylphosphino)benzylamine] palladium(II)
Authors: Takenaka Akio , Sasada Yoshio , Yamamoto Keiji , Tsuji Jiro 
Published: July 2006

Abstract
The crystal structure of dichloro[N, N-dimethyl-α-methyl-o-(butylphenylphosphino)benzylamine]palladium-(II) has been determined from MoKα diffraction data. The space group is P21 with Z=2, a=9.255(2), b=14.372 (3), c=8.584(1) Å, and β=105.99(1)°. The final R became 0.034 by least-squares refinement. The Pd atom has a square planar coordination of N, P, and two Cl atoms, which is considerably distorted by the intramolecular atomic repulsions. The Pd–N distance, 2.134(4) Å, which is longer than those found so far, is accompanied by a short distance 2.285(1) Å of trans Pd–Cl. A plot of Pd–Cl distance versus trans Pd–N distance in several Pd complexes, in which the nitrogen atom is not π-acceptor, shows a linear relationship with the correlation factor of −0.28(4).
Preparation and Spectroscopic Studies of Four Stereoisomers of Tris[(S)-1,3-butanediamine]cobalt(III) Complex
Authors: Kojima Masaaki , Fujita Junnosuke 
Published: July 2006

Abstract
Four stereoisomers, mer-Δ, mer-Λ, fac-Δ, and fac-Λ, of the tris[(S)-1,3-butanediamine]cobalt(III) complex were obtained, and their absorption and circular dichroism spectra were recorded in water in the absence or presence of sulfate ions. The shift of absorption bands and the variation of circular dichroism spectra caused by the addition of sulfate ions seem to be correlated with the conformational instability of six-membered (S)-1,3-butanediamine chelate rings in the complexes.
The Disproportionation Constants of Mercury(I) in Dilute Solutions
Authors: Sanemasa Isao , Hirata Tsutomu 
Published: July 2006

Abstract
The disproportionation constants for the Hg22+\ightleftarrowsHg(aq)+Hg2+ reaction have been measured in dilute mercury (I) perchlorate solutions over the temperature range from 15 to 30 °C. The technique was based on a simple kinetic method which made use of a characteristic property of the elemental mercury in aqueous solutions. The disproportionation constant at 25 °C and μ=0.1 was found to be 1.1±0.1×10−8 M, and the associated thermodynamic parameters were ΔH=13.2±0.2 kcal/mol and ΔS=8.0 e.u. The reliability of the method was discussed with relation to the reported values in the literature.
A Relationship between the Circular Dichroism and the Configuration of Asymmetric Nitrogen in trans(N,EthyIene)-chloro-l-aminocarboxylato-η2-ethyleneplatinum(II)
Authors: Terai Yoshiro , Kido Hiroaki , Saito Kazuo 
Published: July 2006

Abstract
The circular dichroism (CD) peaks of trans(N, ethylene)[PtCl(l-am)(C2H4)] (l-am, l-amino carboxylate) in acetonitrile (AN) at 33000 and 37000 cm−1 are characteristic of those complexes with asymmetric nitrogen. The CD sign depends on the substituents on the asymmetric nitrogen, and the additivity law holds for methyl and benzyl derivatives of l-prolinato, l-hydroxyprolinato, and l-valinato complexes. The quadrant rule is applicable to the contribution of the substituents on the nitrogen. On the preparation of the benzyl-l-valinato complex from Zeise’s salt in a weakly acid medium the nitrogen exhibits a marked stereoselectivity to give R configuration.
The Direct Chlorination of Anthraquinone Oxime. The Regioselective Chlorination of Anthraquinone
Authors: Ito Takehiko , Sadakata Koichi , Kindaichi Yoshiaki , Takami Yasuo 
Published: July 2006

Abstract
The reaction of anthraquinone oxime with chlorine in the presence or absence of a catalyst was investigated. In concentrated sulfuric acid, the direct chlorination of anthraquinone oxime takes place easily at 100 °C. The chlorination occurs selectively in the β-position in the absence of a catalyst and in the α-position in the presence of palladium acetate.
Synthesis and Hydrolysis of 4-Acetoxymethylbenzimidazoles, Effects of Freezing an Internal Rotation on Intramolecular Catalysis by a Benzimidazolyl Group
Authors: Utaka Masanori , Takatsu Masahisa , Takeda Akira 
Published: July 2006

Abstract
As models for acetyl-α-chymotrypsin, 4-acetoxymethylbenzimidazole (2), its 5-methyl derivative 3 and 2,5-dimethyl derivative 4 were synthesized from o-toluidine in moderate yields. Their hydrolytic reactivities were determined in water at 50 °C in comparison with their open-chain analog, 4-(acetoxyethyl)imidazole(1). The rate constant (k1) for intramolecular general base catalysis by the imidazolyl group of 2 was 1.6 times larger than k1 for 1. A corrected relative rate of 4.1 is obtained by correcting the basicity difference and the polar substituent effect. The value of 4.1 is an expected magnitude of the effect of freezing an internal rotation as reported for 4,5-(1-acetoxymethyltetramethylene)imidazole. The 5-methyl group of 3 enhances the k1 value 1.4 times as large as that for 2. The enhancement can be attributed to restriction of the second internal rotation. The hydrolytic reactivity of 4 is discussed.
Substituent Effects on Tautomerism of 4-Pyridinethiones
Authors: Besso Hiromichi , Imafuku Kimiaki , Matsumura Hisashi 
Published: July 2006

Abstract
The tautomeric constants Kt of several 4-pyridinethiones were determined by measurement of pKa values. For 2-substituted 5-methoxy-4-pyridinethiones, the Kt values are correlated to the substituent constants σ, by the equation logKt=4.00+3.99σm−7.33σ0.
Aminosugars. XXVIII. A Facile Synthesis of Benzyl α- and β-Kasugaminides via the Corresponding Abequosides
Authors: Yoshimura Juji , Sato Ken-ichi , Hashimoto Hironobu , Shimizu Kuniaki 
Published: July 2006

Abstract
Synthesis of benzyl α- and β-kasugaminides (benzyl 2,4-diamino-2,3,4,6-tetradeoxy-α- and β-d-arabino-hexopyranosides) was carried out by the simultaneous substitution at 2,4-positions of 2,4-di-O-mesyl-abequosides (3,6-dideoxy-2,4-di-O-mesyl-α- and β-d-xylo-hexopyranosides) with sodium azide followed by hydrogenation. The substitution in N,N-dimethylformamide at higher temperature gave the elimination products (4-azido-2,3-unsaturated derivatives) and the subsequently rearranged products (3,4-unsaturated 2-azido derivatives), but, that in hexamethylphosphoric triamide at lower temperature gave the desired compounds in fairly good yields.
Layered Compounds. XLIV. Transannular π-π Interactions in Tetracyanoethylene Complexes of [m.n]Paracyclophadiynes and the Related Cyclic Acetylenes
Authors: Kaneda Takahiro , Misumi Soichi 
Published: July 2006

Abstract
The electronic spectra of TCNE complexes of acyclic and cyclic diacetylenes and cyclic tetraacetylenes were measured. They show a maximum in the narrow region 423–431 nm regardless of ring strain in the donor molecules and proximity of two diacetylene groups. Crystalline two-to-one TCNE complexes of [m.n]paracyclophadiynes were prepared, the formation of one-to-one TCNE complexes in solution being established by means of the Benesi-Hildebrand plots using various molar ratios of the two components. The electronic spectra of some 1: 1 [m.n]paracyclophadiyne–TCNE complexes were measured. The spectra suggest that the complexes are equilibrium mixtures consisting of three isomeric complexes, i.e., a diacetylene-site complex and two pseudo-conformers of benzene-site complex. The longer wavelength band of [m.n]paracyclophadiyne complexes shows a marked red-shift as compared with the other bands. This is interpreted in terms of transannular π-π interaction between the diacetylene group and the benzene ring fixed closely with each other by shortening of methylene bridges. The contribution of the three isomeric complexes on the red-shift is discussed.
The Reaction of Dammarane Derivatives: Reactions Involving C-20 Carbdnium Ions
Authors: Tori Motoo , Tsuyuki Takahiko , Takahashi Takeyoshi 
Published: July 2006

Abstract
In order to investigate the reaction involving C-20 cation in dammarane derivatives, following reactions were examined: a) (20S)- and (20R)-dammaran-20-ols (13 and 14) with acids, b) dammar-20(22)-en-23-one (15) with hydrochloric acid, c) 20,21- and 20,22-epoxydammaranes (16 and 17) with boron trifluoride etherate, and d) hexanor- and pentanordammaran-20-ols (18 and 19) with phosphoryl chloride and with boron trifluoride etherate, etc., and 20ξ-tosyloxyhexanordammarane (46) with silica gel. Either formation of a double bond in the framework or in the side chain (in the cases of 13, 14, 18, 19, and 46), deconjugation of the double bond (in the case of 15), or formation of a carbonyl group in the side chain (in the cases of 16 and 17) was observed. However, D-homoannulation reaction was not observed in all cases.
A Macrocyclic Enzyme Model System. Deacylation of p-Nitrophenyl Carboxylates as Effected by a [20]Paracyclophane Bearing an Imidazole Group
Authors: Murakami Yukito , Aoyama Yasuhiro , Kida Masaaki , Nakano Akio 
Published: July 2006

Abstract
The kinetic effect of a [20]paracyclophane bearing an imidazole moiety (1) on the deacylation of various p-nitrophenyl carboxylates was investigated in 10.9% (v/v) ethanol-1.0%(v/v) dioxane-water of μ 0.10 (KCl) at 40.0±0.1 °C. The facile reaction of 1 with a hydrophobic ester resulted in the accumulation of the NIm-acyl derivative of 1 along the progress of reaction, and the rate of regeneration of 1 (turnover) was negligibly small under present experimental conditions compared to the corresponding acylation rate. The overall feature for deacylation reactions of p-nitrophenyl carboxylates bearing a hydrophobic acyl moiety in the presence of 1 is consistent with the reaction scheme which involves the reactions of the monomeric and aggregated forms of 1 with substrate esters. The second-order rate constants for reactions of the monomeric species of 1 with relatively hydrophobic esters exceed considerably the corresponding second-order rate constants for imidazole-catalyzed reactions, suggesting the significant hydrophobic interaction between 1 and each hydrophobic ester. The binding constants (K) for complex formation of a micelle (aggregation number, N) with significantly hydrophobic substrates are greater than 105 M−1. The second-order rate constants (kmK⁄N) for reactions of the imidazole group of 1 with the long-chain carboxylates in micellar phase are the largest ever achieved for reactions of synthetic 4-substituted imidazoles with p-nitrophenyl esters.
Reactions of 4-Acyl-2-phenyl-1,3,4-oxadiazoline-5-thiones with Alcohols in the Presence of Metal Ions
Authors: Fukuda Hiroyuki , Endo Takeshi , Okawara Makoto 
Published: July 2006

Abstract
4-Acetyl- and 4-benzoyl-2-phenyl-1,3,4-oxadiazoline-5-thiones reacted with alcohols in the presence of metal ions to give the corresponding esters in good yields.
A Convenient Synthesis of 1-(2′,3′-Dideoxy-β-d-erythro-hex-2′-enopyranosyl)uracil
Authors: Yamazaki Tatsumi , Sugiyama Hiroshi , Matsuda Kazuo , Seto Shuichi 
Published: July 2006

Abstract
2,2′-Anhydro-l-(4′,6′-O-benzylidene-3′-O-methylsulfonyl-β-d-mannopyranosyl)urasil, prepared smoothly from β-d-glucopyranosyluracil in three steps, was converted into the corresponding unsaturated nucleoside in a good yield by the action of sodium iodide. The unsaturated nucleoside was then debenzylidenated with acid to afford the title compound.
Reaction of Bis(trans-1-hexenyl)methylborane with Two Molar Equivalents of Methylcopper(I). Evidence for the Presence of trans-1-Hexenylcopper(I) as an Intermediate
Authors: Yamamoto Yoshinori , Yatagai Hidetaka , Maruyama Kazuhiro , Sonoda Akio , Murahashi Shun-Ichi 
Published: July 2006

Abstract
Bis(trans-1-hexenyl)methylborane, prepared by the reaction of bis(trans-1-hexenyl)chloroborane with methyllithium, was treated with 2 molar equivalents of methylcopper(I) at −78 °C to give (5E,7E)-5,7-dodecadiene quantitatively. The result indicates the presence of trans-1-hexenylcopper(I) intermediate.
Thermal Dissociation of N,N-Dimethylformamide–Tetracyanoethylene and Dimethyl Sulfoxide–Tetracyanoethylene Complexes into Ions
Authors: Kushibiki Nobuo , Yoshida Hiroshi 
Published: July 2006

Abstract
Ionic dissociation of N,N-dimethylformamide (DMF)–tetracyanoethylene (TCNE) and dimethyl sulfoxide (DMSO)–TCNE electron donor-acceptor (EDA) complexes was studied by means of optical absorption and electron spin resonance measurements. Upon dissolving TCNE into DMF or DMSO, essentially all the TCNE became complexed with the electron-donationg solvent; charge-transfer bands with maxima at 310 and 380 nm were found for DMF–TCNE and DMSO–TCNE complexes, respectively. The CT bands were transformed slowly in the dark into the band of TCNE−. This transformation proceeded quantitatively and indicated the dissociation of the EDA complexes into ions. The rate of the ionic dissociation was determined by following a first-order growth of the ESR spectrum of TCNE− at various temperatures: k=108.9exp(79⁄RT) for the DMF–TCNE complex and k=106.3exp(59⁄RT) for the DMSO–TCNE complex, in units of s and kJ/mol. Dissolved oxygen was found not only to react chemically with the complex to form a new stable species, but also to quench physically the ionic dissociation. Upon evacuating the oxygen, the survival fraction of the complex was found to start dissociation again. It is suggested that the ionic dissociation arises from a long-lived precursor state, probably the triplet state of the complex.
The Vibrational Spectra of Tetracyanothiophene
Authors: Nakanishi Jiro , Takenaka Tohru 
Published: July 2006

Abstract
The polarized infrared and far-infrared spectra of the tetracyanothiophene (TCNT) crystals were recorded by means of the normal and oblique incidence of radiation upon the (001) and (20\bar1) sample planes. The Raman spectra of the powdered sample and of a saturated solution in acetonitrile or 1,2-dichloroethane were also obtained. The observed bands were experimentally classified into the symmetry species of the free molecule (the point group C2v) under the assumption of an oriented gas model. Assignments of the observed bands to individual fundamental vibrations were carried out with the aid of the spectral data of the analogous molecules and the normal coordinate analysis of the in-plane vibrations, which was made with a modified Urey-Bradley force field.
Stereochemical Studies of the Electrolytic Reactions of Organic Compounds. II. Electrolytic Reduction of Optically Active 6-Chloro-2,6-dimethyloctane to the Corresponding Alkane
Authors: Nonaka Tsutomu , Ota Tetsuro , Odo Keijiro 
Published: July 2006

Abstract
In order to clarify the mechanism of electroreduction of aliphatic halides, optically active 6-chloro-2,6-dimethyloctane(I), in which an (R)-(−)-enantiomer was present in excess, was electrolyzed at a mercury cathode in various organic solvents. An (R)-(−)-enantiomer was also present in excess in the 2,6-dimethyloctane(II) which was obtained. This result indicates that the reduction of I to II proceeds with an excess of the inversion of the absolute configuration of the starting halide. In this paper, the stereochemistry of a radical intermediate formed at an initial stage in the course of reduction is discussed.
Synthesis of Tuftsin and Its Analogs
Authors: Nozaki Sukekatsu , Hisatsune Kazuhito , Muramatsu Ichiro 
Published: July 2006

Abstract
Tuftsin, a phagocytosis stimulating peptide, was synthesized according to a liquid phase method together with its four analogs, H–Thr–Arg–Pro–Arg–OH (2), H–Thr–Lys–Pro–Lys–OH (3), H–Thr–Arg–Pro–Lys–OH (4), and H–Arg–Pro–Lys–Thr–OH (5).
Carbon-Nitrogen Bond Fission in Ureas and Thioureas. Preparation of Alkyl and Aryl Isothiocyanates Using Carbon Bisulfide and Butyllithinm or a Grignard Reagent
Authors: Sakai Shizuyoshi , Fujinami Tatsuo , Aizawa Toshiyuki 
Published: July 2006

Abstract
The carbon-nitrogen bond in N,N′-diaryl- and dialkyl-thioureas or -ureas was easily cleaved by the metallation of thioureas or ureas using butyllithium, followed by the addition of an excess of carbon disulfide or 1,3-dithiolan-2-thione in tetrahydrofuran under reflux, to afford about two mol of the corresponding isothiocyanates per mol of the thioureas or ureas used. Instead of butyllithium, ethylmagnesium bromide was also effective in such a type of carbon-nitrogen bond fission of the (thio) ureas in refluxing tetrahydrofuran, and in this case the addition of carbon disulfide was not required. To explain these results, a six-centered decomposition of the dilithium salt of N-dithiocarboxy(thio) urea in the reaction using butyllithium was tentatively proposed, while a four-centered mechanism seems applicable to the reaction using ethylmagnesium bromide.
Seven-membered N-Heterocycles. XIII. Rearrangement of 7-Benzyl-4-hydroxy-6,7,8,9-tetrahydro-5H-pyrimido[4,5-d]azepines to 7-Benzyl-4-vinyl-6,7-dihydro-5H-pyrrolo[2,3-d]pyrimidines
Authors: Yamamoto Hiroshi , Kawamoto Heizan , Morosawa Shiro , Yokoo Akira 
Published: July 2006

Abstract
The title pyrimidoazepines when treated with phosphoryl chloride underwent rearrangement to the vinylpyrrolo-pyrimidines via probable intermediates 5-(2-benzylaminoethyl)-4-chloro-6-vinylpyrimidines. Reduction and subsequent dehydrogenation of the products led to the preparation of 4-ethyl-7H-pyrrolo[2,3-d]pyrimidines and their 5,6-dihydro derivatives. The structures are discussed on the basis of pKa values, UV and NMR spectra.
Synthesis of Ripariochromene B and C
Authors: Tsukayama Masao 
Published: July 2006

Abstract
Condensation of 7-hydroxy-2,2-dimethylchroman with benzoyloxyacetonitrile gave 7-hydroxy-6-benzoyl-oxyacetyl-2,2-dimethylchroman (3) which was converted into 7-hydroxy-6-acetoxyacetyl-2,2-dimethylchroman (7) in four steps. Dehydrogenation of 7 with DDQ in dried toluene afforded ripariochromene B (1). Ripariochromene B was also synthesized by oxidative cyclization of 2,4-dihydroxy-5-(3-methyl-2-butenyl)-ω-acetoxy-acetophenone (13) which was prepared from resorcinol and acetoxyacetonitrile in two steps. Ripariochromene C (2) was synthesized from resorcinol by the same method as that described above.
Skeletal Rearrangement of Furanoeremophilane-6β,10β-diol into Farfugin A, Farfugin B, and 6-[(4R)-Chloropentyl]-3,5-dimethylbenzofuran
Authors: Tada Masahiro , Tanahashi Yoshiaki , Moriyama Yoshihiko , Takahashi Takeyoshi 
Published: July 2006

Abstract
Treatment of furanoeremophilane-6β,10β-diol (1; R=H) with phosphoryl chloride in pyridine at 110 °C gave farfugin A (2; yield: 23%), farfugin B (3; y: 34%), and 6-[(4R)-4-chloropentyl]-3,5-dimethylbenzofuran (4; y: 15%). A mechanism of formation of these three compounds (2, 3, and 4) is discussed.