Showing papers in "Bulletin of the Chemical Society of Japan in 1976"

Nickel-phosphine complex-catalyzed Grignard coupling. I. Cross-coupling of alkyl, aryl, and alkenyl Grignard reagents with aryl and alkenyl halides: General scope and limitations.

Abstract: It has been established that dihalodiphosphinenickel(II) complexes exhibit extremely high catalytic activity for selective cross-coupling of Grignard reagents with aryl and alkenyl halides. This catalytic reaction can be employed in synthetic practice for reasons of simple procedures, mild reaction conditions, high yields and high purity of the coupling products, and the wide applicability to reactions involving primary and secondary alkyl (regardless of the presence or absence of β-hydrogen (s)), aryl, and alkenyl Grignard reagents and nonfused, fused, and substituted aromatic halides and haloolefins. Limitations lie in sluggish reactions between alkyl Grignard reagents and dihaloethylenes. The most effective catalysts are [Ni{(C6H5)2P(CH2)3P(C6H5)2}Cl2] for alkyl and simple aryl Grignard reagents, [Ni{(CH3)2P(CH2)2P(CH3)2}Cl2] for alkenyl and allylic Grignard reagents and [Ni{P(C6H5)3}2-Cl2] for sterically hindered aryl Grignard reagents and halides. Great stabilizing effects of phosphine ligands on the...

X-Ray Diffraction Studies of the Structures of Hydrated Divalent Transition-Metal Ions in Aqueous Solution

Abstract: X-ray scattering measurements have been carried out for concentrated aqueous solutions of divalent transition-metal perchlorates of manganese(II) to zinc(II). The radial distribution curves showed that each central metal ion was octahedrally surrounded by six water molecules at the distances of 2.20 A for Mn2+–OH2, 2.12 A for Fe2+–OH2, 2.08 A for Co2+–OH2, 2.04 A for Ni2+–OH2, and 2.08 A for Zn2+–OH2. The results from the radial distribution curves were confirmed by the direct analysis of reduced intensities. Concentrated aqueous solutions of copper(II) and zinc(II) sulfates have also been measured. The bond distances of 1.94 A for the Cu2+–OH2 (equatorial), 2.38 A for the Cu2+–OH2 (axial) and 2.08 A for Zn2+–OH2 were consistent with those obtained for the perchlorate solutions. No evidence for the contact ion pairs of metal and sulfate ions was found by the present X-ray measurements. The bond energies between metal ions including copper ion were discussed by application of the Garrick model with a sligh...

Electronic spectra and electronic structure of TCNQ complexes.

Abstract: Electronic spectra of several TCNQ, complexes have been measured with single crystals by the transmission method. The assignment of electronic transitions are presented based on the electronic stru...

Reaction of dimethylphenacylsulfonium bromide with N-nitrosoacetarylamides and reactions of the products with nucleophiles.

Abstract: The azo coupling of dimethylphenacylsulfonium bromides (I) with N-nitrosoacetanilides in nonaqueous solvents, and with diazotized aniline in aqueous media gave 2-bromophenylglyoxal 2-arylhydrazones (V) and the tetrazine (VI), respectively. V reacted with nucleophiles displacing the bromide. Treatment of V with bases gave VI via benzoylphenylnitrilimine (X). 1,3-Dipolar cycloadditions of X onto ethyl acrylate and acrylonitrile afforded the expected cycloadducts. The mechanisms of the reactions are outlined.

Thermal Cis-to-Trans Isomerization of Substituted Azobenzenes II. Substituent and Solvent Effects

Abstract: The thermal cis-to-trans isomerization rate of various azobenzenes was followed by means of spectrophotometric and flash photolysis techniques. For para-donor/para′-acceptor-substituted azobenzenes such as 4-nitro-4′-dimethylaminoazobenzene, the rate was distinctly accelerated, the activation energy decreasing with the increase in the polarity of solvents. Introduction of substituents in para positions with respect to azo group increased the rate irrespective of substituent. The effect is additive and a Hammett-type equation holds. For 4-dimethylamino-and 4-nitroazobenzenes, while the 2-methyl group accelerated the rate, the 2′-methyl group did not. The results suggest that the isomerization proceeds via inversion mechanism and the rate is controlled mainly by the resonance stabilization in the coplanar transition state. The inversion center for asymmetric azobenzenes is discussed.

The Michael Reaction of Silyl Enol Ethers with α,β-Unsaturated Eetones and Acetals in the Presence of Titanium Tetraalkoxide and Titanium Tetrachloride

Abstract: Silyl enol ethers react with α,β-unsaturated ketones and esters in the presence of TiCl4 or in the coexistence of TiCl4 and Ti(Oi-Pr)4 to give 1,5-dicarbonyl compounds in good yields The reactions of acetals derived from α,β-unsaturated ketones with silyl enol ethers in the coexistence of TiCl4 and Ti(Oi-Pr)4, followed by successive addition of 1,2-ethanedithiol, give the Michael products, δ-keto ethylene thioacetal, in good yields The reaction of silyl enol ethers with acetals derived from α,β-unsaturated aldehydes also gives the Michael products when Ti(OCEt3)4 is employed instead of Ti(Oi-Pr)4 in the above experiment and is successfully applied to the simple synthesis of dihydro rose oxide

Photoelectrochemical Reactions at SrTiO3 Single Crystal Electrode

Abstract: Electrode characteristics of strontium titanate (SrTiO3) single crystal have been investigated under illumination with light of its intrinsic absorption region. It has been found that the photosensitized electrolytic oxidation of water, known heretofore uniquely on the TiO2 electrode, can proceed also at the SrTiO3 electrode whose anodic dissolution being negligible. Although the photosensitivity of the SrTiO3 electrode is confined to a little shorter wavelength region than that of the TiO2 electrode, the formal quantum efficiency of the photosensitized electrolytic oxidation of water is comparable for these two semiconductor electrodes under intrinsic absorption. In contrast to the case of the TiO2 electrode, the electrochemical photocell consisted of the SrTiO3 anode and platinum cathode can work efficiently even when the pH values of the anodic and cathodic compartments are close to each other. This point is discussed in terms of the flatband potential of these semiconductor electrodes.

Chemical Synthesis of N-Acetylmuramyl Peptides with Partial Structures of Bacterial Cell Wall and Their Analogs in Relation to Immunoadjuvant Activities

Abstract: N-Acetylmuramyl peptides of successive length corresponding to the partial structures of cell wall in Staphylococcus aureus were synthesized in order to elucidate the minimum effective structure responsible for immunoadjuvant activity of bacterial cell walls. In view of the finding that N-acetylmuramyl-L-alanyl-D-isoglutamine was the least structure moiety for exhibition of the activity, nine analogs of either N-acetylmuramyl amino acid or N-acetylmuramyl dipeptide were also synthesized.

Emission spectra of the vinyl polymers with pendant carbazolyl groups.

Abstract: The emission properties of poly(N-vinylcarbazole) (PVCz) prepared by radical and cationic polymerization (PVCz(r) and PVCz(c) respectively), the oligomers of N-vinylcarbazole, and poly[2-(N-carbazolyl)ethyl vinyl ether] (PCzEVE) were investigated in solutions. The fluorescence spectrum of PVCz(r) was different from that of PVCz(c). This seems to be attributable to the difference in the tacticity between them. On the basis of this result, the structure of the second excimer site is discussed. PCzEVE, in which the carbazolyl chromophores are widely spaced on the skeletal chains by –O–CH2–CH2– bonds, showed an interesting, new, structureless emission band with a peak at 27000 cm−1. This was different from both the monomeric structured fluorescence and the sandwich-like excimer one which were observed for the model compounds and the polymers. The emission properties of PCzEVE were unique among the vinyl polymers with aromatic chromophores widely spaced on the skeletal chain.

Picosecond Flash Spectroscopy of Solvent-Induced Intramolecular Electron Transfer in the Excited 9,9′-Bianthryl

Abstract: Sn←S1 absorption spectra of 9,9′-bianthryl in the visible and near infrared regions have been measured by means of picosecond flash spectroscopy. The Sn←S1 spectra in hexane measured at 500 ps after the exciting pulse were similar to those of anthracene while those in acetone were similar to the superposition of spectra of anthracene anion and cation. The results of the Sn←S1 spectral measurements together with those of the solvent effects upon the fluorescence yield and lifetime indicate an intramolecular electron transfer induced by the interaction with polar solvents in the excited state of 9,9′-bianthryl.

Preparation of 2,3,4,6-Tetra-O-benzyl-D-mannose

Abstract: 2,3,4,6-Tetra-O-benzyl-D-mannopyranose was prepared from methyl α-D-mannopyranoside. Improved preparations of 2,3,4,6-tetra-O-benzyl-α-D-glucopyranose and -galactopyranose are described.

The Oxidation Activity and Acid-base Properties of Mixed Oxide Catalysts Containing Titania. I. The TiO2–MoO3 and TiO2–V2O5 Systems

Abstract: The amounts of both the acidic and basic sites of two series of catalysts, TiO2–MoO3 and TiO2–V2O5, with different compositions were measured by studying the adsorption of the basic and acidic molecules in the gas phase, using both the static and pulse methods. The acidity of TiO2–MoO3 catalysts is very high at Mo=40–60 atom%, though those of the TiO2-rich (Mo 80 atom%) catalysts are fairly low. The acidity of the TiO2–V2O5 increases steadily with the V2O5 content. The basicity of the catalysts is remarkably enhanced by the introduction of a small amount of MoO3 or V2O5. It can be said that the catalysts are basic at Mo<20 atom% or V<10 atom%, while the MoO3-rich or V2O5-rich catalysts are acidic. The vapor-phase oxidation of 1-butene, butadiene,and acetic acid, the dehydration and dehydrogenation of isopropyl alcohol (IRA), and the isomerization of 1-butene were carried out in the presence of an excess of air, and the relationship between the catalytic behavior and the acid-ba...

A facile synthesis of 2,5-disubstituted tetrazoles by the reaction of phenylsulfonylhydrazones with arenediazonium salts.

Abstract: 2,5-Disubstituted tetrazoles are obtained in good yields by the reaction of phenylsulfonylhydrazones of aromatic aldehydes (and cinnamaldehyde) with arenediazonium salts. From the synthetic viewpoint for tetrazoles, this method may be of high synthetic utility on account of the availability of starting materials, the simplicity of procedure, and higher yields.

Solid-State Circular Dichroism Spectra of Tris(diamine)cobalt(III) Complexes: Decomposition into E and A2 Components

Abstract: Solid-state circular dichroism spectra of some tris(diamine) cobalt(III) complexes were measured. Each CD band region was decomposed into E and A2 components by combining the CD spectra in uniaxial single-crystals and in microcrystalline states. The observed values of R(E) and R(A2) were compared with the theoretical calculation of Mason and Seal based on dynamic coupling method. The agreements are generally good for those complexes with five-membered chelate rings, however, there are some discrepancies for six- and seven-membered chelate ring cases.

The Crystal and Molecular Structure of Chloro-α,β,γ,δ-tetraphenylporphinatocobalt(III)

Abstract: The structure of the title compound, C44H28N4CoCl, has been determined by single-crystal X-ray diffraction. The crystals are body-centered tetragonal, with a=b=13.693(2), c=9.701(2) A, and Z=2. The space group was determined to be I4 from the measurement of the anomalous dispersion effect. The structure was predicted prior to the X-ray analysis from the calculation of the intermolecular van der Waals energy; the result agreed quite well with the experimentally determined structure. A tetragonal pyramidal five coordination with the chlorine atom at the apex was found for the cobalt atom. The cobalt-chlorine distance is 2.149 (6) A, about 0.1 A shorter than those found in ordinary octahedral coordinations.

An Improved Synthesis of Dibenzoxanthene

Abstract: 14H-Dibenzo[a,j]xanthene was easily synthesized by heating alkali (K or Na) 2-naphthyloxide under CO and CO2 pressure.

On the Solvent-Induced Changes of Electronic Structures of Intramolecular Exciplexes

Abstract: Effects cf solvent polarity upon the electron donor-acceptor interactions in the excited state of p-(CH3)2N C6H4(CH2)n-(9-anthryl) (n=0, 1, 2, 3) and p-(CH3)2NC6H4-(CH2)n-(1-pyrenyl) (n=1, 2, 3) have been investigated by means of fluorescence spectral measurements and theoretical calculations based on some simplified models. The solvent-induced electronic structural changes during the excited state lifetime have been demonstrated for some of the above intramolecular exciplexes.

X-Ray Photoelectron Spectroscopic Studies of Catalysts—Chromia–Alumina Catalysts—

Abstract: The XPS studies of chromia–alumina catalysts were carried out to elucidate the surface of these catalysts. Photoreduction was found to occur during the XPS measurements. Therefore, all spectra were measured rapidly to prevent any photoreduction. It was found that the information about the spin-orbit splitting of the Cr2P level is very useful for determining the valence state of chromium. The surface state of chromium in chromia–alumina catalysts calcined at 500 °C for 5 h is predominantly Cr6+ at low chromia concentration catalysts. However, the Cr3+ phase appears in catalysts of higher chromium content, and the surface concentration of Cr3+ increases with increasing content of supported chromia. The XPS spectra due to Cr5+ were observed after mild reduction of the catalysts. Moreover, it was found that almost all surface chromium is present as Cr5+ at low chromia content catalysts after mild reductions. Qualitatively, the results obtained by the XPS technique, which gives information about the surface of...

Epoxide Rearrangement III. Isomerization of 1-Methylcyclohexene Oxide over TiO2–ZrO2, NiSO4 and FeSO4

Abstract: The reaction of 1-methylcyclohexene oxide at 108 °C was found to give predominantly 2-methylcyclohexanone (III) over FeSO4, but predominantly allyl alcohols (VI) over TiO2–ZrO2 of various compositions. NiSO4 gave the same amount of both products, III and VI. The selectivities over FeSO4 and NiSO4 were not much varied with calcination temperatures from 150 °C to 700 °C, while the catalytic activities were higher with NiSO4 calcined at low temperature and with FeSO4 calcined at high temperature. FeSO4 and NiSO4 gave the preferential formation of an allyl alcohol with exo-double bond, 2-methylene cyclohexanol (VIa), while TiO2–ZrO2 formed predominantly an allyl alcohol with endo-double bond, 2-methyl-2-cyclohexene-1-ol (VIb). Both the acidity and basicity of TiO2–ZrO2 were observed to increase by mixing each oxide and to correlate with the catalytic activity. The allyl alcohol formation was explained by an acid-base bifunctional mechanism.

Preparation of Hindered Esters from Acid Chlorides and Alcohols in the Presence of Silver Cyanide

Abstract: Sterically hindered esters were prepared from the corresponding acyl chlorides and alcohols in the presence of silver cyanide. The method is superior to the conventional acyl chloride–alcohol–pyridine method as regards yield and the rapidity of reaction.

Stereoselective and Stereospecific Reactions. III. Benzoylation, Cyclfzation, and Epimerization of Diols

Abstract: The benzoylation of various classes of diols by means of diethyl azodicarboxylate (1) and triphenylphosphine (2) was carried out at room temperature. When primary–secondary diols were treated with an equimolar amount of benzoic acid (3) in the presence of 1.5 molar equivalents of 1 and 2, reaction mainly Occurred at their primary hydroxyl functions. Secondary–secondary diols gave mono- and dibenzoylated products or cyclic ethers. The course of the reactions depends on the structure of diols used. Thus, intermolecular displacement giving benzoates is a favorable process for 1,3-butanediol, 2,4-pentanediol and trans-1,2-indanediol, while 2,5-hexanediol and trans-1,2-cyclohexanediol afford the cyclized products.

The Structure and Reactivity of [Zn(OMe)2·(EtZnOMe)6]

Abstract: The molecular structure of [Zn(OMe)2·(EtZnOMe)6], an enantiomorphic catalyst for the polymerisation of methyloxirane, has been determined.

On the Number of Aromatic Sextets in a Benzenoid Hydrocarbon

Abstract: For a benzenoid hydrocarbon with a single sextet formula, the number of aromatic sextets in it is very close to the number of sextet-type resonance interactions per Kekule structure

Photochemical Cycloaddition Reactions of α,β-Unsaturated Lactones with Olefins, and Application to Synthesis of Natural Products

Abstract: The photochemical cycloaddition reactions of five- and six-membered α,β-unsaturated lactone derivatives with unsaturated substrates (ethylene, acetylene, 1,1-dimethoxyethylene etc.) have been studied. The parent α,β-unsaturated lactone (γ-crotonolactone) and the β-,γ-, or δ-alkyl substituted derivatives add to ethylene and acetylene in the acetone solutions and to 1,1-dimethoxyethylene in the benzene solutions in so good yields as to utilize them practically for synthesis. α-Phenyl-γ-crotonolactone and β-phenyl-γ-crotonolactone also add to ethylene and acetylene, whereas, α-methyl, β-hydroxy, and β-methoxy derivatives do not. As the synthetic applications of the reactions, the synthesis of (±)-grandisol has been achieved, and the synthetic approach to (±)-canadensolide has also been described.

Synthesis and Properties of Organocobalt(III)octaethylporphyrins

Abstract: The syntheses of alkylcobalt(III)octaethylporphyrins(OEP) via nucleophilic attack of the Co(I) complex to unsaturated compounds are reported. Olefins with an electron-withdrawing group and acetylenes react with Co(I)(OEP), whereas olefins with an electron-donating group such as propylene and cyclohexene are unreactive. A novel ring cleavage of cyclopropyl methy ketone initiated by Co(I)(OEP) affords alkylCo(III)(OEP). The reduction of cobalt(II) N-methyloctaethylporphyrin acetate results in intramolecular methyl migration from nitrogen to the central cobalt atom. Five-coordination has been established for the organocobalt(III)(OEP) complexes on the basis of their analytical, infrared and NMR data. Some anomalous behavior of the proton signals of the α-carbon atom in their NMR spectra has been discussed in terms of quadrupolar relaxation and electronegativity of the cobalt ion.

Binuclear Metal Complexes. XV. Copper(II) and Nickel(II) Complexes of Binucleating Ligands Derived From 3-Formyl-salicylic Acid and Diamines

Abstract: Copper(II) and nickel(II) complexes of the 3-formylsalicylic acid-diamine Schiff bases, H4fsaen, H4fsapn, H4fsatn, H4fsaph, and H4fsach, where en, pn, tn, ph, and ch denote ethylenediamine, propylenediamine, trimethylenediamine, o-phenylenediamine, and 1,2-cyclohexanediamine respectively, have been obtained and characterized. Binuclear copper(II) complexes, Cu2(fsaen)·2H2O, Cu2(fsapn)·2H2O, Cu2(fsatn)·2H2O, Cu2(fsaph)·H2O, and Cu2(fsach)·2H2O, show a strong antiferromagnetic spin-exchange interaction between metal ions, −2J values being more than 555 cm−1. It was revealed that Ni2(fsaen)·3H2O, Ni2(fsapn)·3H2O, Ni2(fsaph)·5H2O, and Ni2(fsach)·3H2O are novel binuclear complexes composed of one paramagnetic and one diamagnetic nickel(II) ions. On the other hand, Ni2(fsatn)·5H2O is a binuclear complex of paramagnetic nickel(II) ions. Its magnetism obeys the Curie-Weiss law in the range from liquid nitrogen temperature to room temperature with the Weiss constant of −40 K.

pH-Dependence of spectral sensitization at semiconductor electrodes.

Abstract: For an interpretation of the pH-dependence of the sensitized photocurrent at semiconductor electrodes, measurements have been carried out on n-type TiO2 and CdS single crystal electrodes. As sensitizing dyes, rhodamine B and 3,3′-diethylthiacarbocyanine iodide which remain stable in a sufficiently wide pH range were used. It has been found that the logarithm of the sensitized photocurrent at TiO2 electrode depends linearly on the pH of the electrolyte solution, whereas the sensitized photocurrent shows practically no pH-dependence at CdS electrode. These observations have been accounted for on the basis of the different pH-dependence of flatband potentials of these semiconductor electrodes.

The Structure of the Cyclodextrin Complex. III. The Crystal Structure of the α-Cyclodextrin-Sodium Benzenesulfonate Complex

Abstract: The crystal structure of the α-cyclodextrin-sodium benzenesulfonate complex, which has a channel-type structure, was determined by X-ray analysis. The crystals were orthorhombic with the space group of P21212, cell dimensions of a=21.832(3), b=16.529(2), and c=8.356(1) A, and Z=2. The structure was determined on the basis of 2894 diffractometer data and refined by the block-diagonal least-squares methods to the final R-value of 0.069. The benzenesulfonate anion is arranged in the channel which is formed by the stack of α-cyclodextrin rings along the c axis. The benzene ring is located in the cavity, while the sulfonato group is hydrogen-bonded to the primary hydroxyl groups of the adjacent α-cyclodextrin molecule. The space outside the channel is filled with water molecules and sodium ions, and the hydrogen-bonding network is formed. The energy of the complex formation was calculated for two possible structures of the 1 : 1 complex in an aqueous solution.

1,3-Benzodithiolylium Salts. Synthesis and Reactions with Nucleophilic Reagents

Abstract: Various salts of 1,3-benzodithiolylium ion were prepared in excellent yields on treatment of 2-alkoxy- and 2-alkylthio-1,3-benzodithioles with acids in acetic anhydride. The reactions of 1,3-benzodithiolylium tetrafluoroborate (1a) with a wide variety of nucleophilic reagents (alcohols, water, thiols, hydrogen sulfide, primary, secondary, and tertiary amines, ammonia, N,N-dimethylformamide, electron-rich aromatic compounds, active methylene compounds, tropilidene, and sodium borohydride) were studied. In all cases examined, 1a reacted with nucleophilic reagents at the 2-position to give the corresponding 1,3-benzodithioles in good yields, excepting the reactions with tertiary amines and N,N-dimethylformamide which resulted in the formation of dibenzotetrathiafulvalene. Salt 1a was also prepared from 1,3-benzodithiole and trityl tetrafluoroborate.

Nucleophilic Displacement Catalyzed by Transition Metal. III. Kinetic Investigation of the Cyanation of Iodobenzene Catalyzed by Palladium(II)

Abstract: The nucleophilic displacement of iodobenzene with potassium cyanide was carried out in HMPA in the presence of palladium(II) acetate. The reaction obeys the following kinetics; d[C_6H_5CN]/dt=k[Pd(OAc)_2]_0(M_KCN)^2/3 A reaction scheme composed of two cycles has been proposed: in one cycle Pd0 activates iodobenzene and in the other cycle Pd2+ assists the dissolution of potassium cyanide.