Showing papers in "Bulletin of the Chemical Society of Japan in 1983"
TL;DR: In this article, a copolymerization of dihalothiophenes and 2,4-dibromothiophene with magnesium dehalogenation is described.
Abstract: Nickel compounds (NiCl2 and NiCl2(2,2′-bipyridine)) catalyze polycondensation of dihalothiophenes (2,5-dihalothiophenes, 2,4-dibromothiophene, and 3-methyl-2,5-dibromothiophene) by dehalogenation with magnesium to give the corresponding poly(thienylene) type polymers (poly(2,5-thienylene), poly(2,4-thienylene), and poly(3-methyl-2,5-thienylene)). Copolymerization of 2,5-dibromothiophene and 2,4-dibromothiophene affords copolymers formulated as (\llap–2,5-C4H2S) \llap–m(\llap–2,4-C4H2S) \llap–n. About 15 wt% of poly(2,5-thienylene) prepared in THF at 66 °C is soluble in CHCl3 at room temperature and the CHCl3-soluble fraction has a molecular weight of 1370. The remaining fraction is considered to have a higher molecular weight as judged from its physical properties. IR and 1H-NMR spectra of the polymers are consistent with the structures described above. The electronic spectra of poly(2,5-thienylene) and poly(3-methyl-2,5-thienylene) show large bathochromic shifts of the π-π* absorption bands from those of...
190 citations
TL;DR: The surface acid properties of Nb2O5·nH2O and its catalytic activities for the isomerization of 1-butene, the polymerization of propylene and the dehydration of 2-butanol were examined in this paper.
Abstract: The surface acidic property of Nb2O5·nH2O and its catalytic activities for the isomerization of 1-butene, the polymerization of propylene and the dehydration of 2-butanol were examined. The activities were high on Nb2O5·nH2O evacuated at moderate temperatures(100–150 °C) in all of the reactions and decreased drastically on evacuation at higher temperatures (400–500 °C). The surface of Nb2O5·nH2O showed a strong acidic character (H0≤−5.6) even after heating in air at 100 °C, but the strong acid sites disappeared on heat treatment at higher temperatures. The active sites on the catalysts heat-treated at moderate temperatures were ascribed mainly to Bronsted acid sites on the basis of the IR study of adsorbed pyridine.
188 citations
TL;DR: Barium manganate is a reagent capable of oxidizing organic substrates, converting alcohols to their corresponding carbonyl compounds, aromatic amines to their respective azo compounds, hydroquinone to p-benzoquinone, benzylamine to benzaldehyde, and triphenylphosphine to its oxide in good yields as discussed by the authors.
Abstract: Preparation of barium manganate in large-scale is discussed. It is also shown that this reagent is capable of oxidizing organic substrates, converting alcohols to their corresponding carbonyl compounds, aromatic amines to their corresponding azo compounds, hydroquinone to p-benzoquinone, benzylamine to benzaldehyde, and triphenylphosphine to its oxide in good yields. Saturated hydrocarbons, unsaturated hydrocarbons, unsaturated ketones, and saturated amines are not affected by this reagent in a reasonable reaction time.
140 citations
TL;DR: Alumina coated with potassium fluoride proved to be a versatile solid base for olefin and acetylene-forming elimination, the Michael addition, aldol condensation, and the Darzens condensation as discussed by the authors.
Abstract: Alumina coated with potassium fluoride proved to be a versatile solid base for olefin- and acetylene-forming elimination, the Michael addition, aldol condensation, and the Darzens condensation.
130 citations
TL;DR: In this article, the infrared spectra of the second stable conformer of 1,3-butadiene-d0, -1,1,4,4-d4, and -d6 were analyzed on the basis of normalcoordinate calculations of the planar s-cis form and a nonplanar gauche form.
Abstract: Normal-coordinate analyses of s-trans-1,3-butadiene and its various deuterated and 13C-substituted analogs were performed using the group-coordinate force field, and a set of force constants was determined. The infrared spectra of the second stable conformer of 1,3-butadiene-d0, -1,1,4,4-d4, and -d6 were analyzed on the basis of normalcoordinate calculations of the planar s-cis form and a nonplanar gauche form. Such an analysis suggests that the second stable conformer takes a gauche form rather than the s-cis. To increase the number of reliable data to be used in this study, the infrared and Raman spectra of the d0, 1,1,4,4-d4, and d6 species were observed in low-temperature Ar matrices. The infrared spectra of the second stable conformer were also observed using a combination of the high-temperature nozzle and low-temperature matrix techniques.
109 citations
TL;DR: In this article, the structure of N,N-dimethylformamide (DMF) was determined at 25 °C by means of X-ray diffraction using a θ-θ type Xray diffractometer, and the least squares analysis of the reduced intensities results that a DMF molecule has a practically planar skeletal structure in the liquid state.
Abstract: The structure of N,N-dimethylformamide (DMF) was determined at 25 °C by means of X-ray diffraction using a θ-θ type X-ray diffractometer. The least-squares analysis of the reduced intensities results that a DMF molecule has a practically planar skeletal structure in the liquid state. Intramolecular structural parameters within a DMF molecule were determined as follows: C=O; 1.24 A, N–C(CHO); 1.35 A, and N–C(CH3); 1.45 A. The bond lengths are not appreciably different from those found in the gas phase, except for the C=O length, which is slightly longer by 0.04 A in the liquid state than in the gaseous one. The radial distribution curve of DMF shows that the intermolecular arrangement of DMF molecules is practically fully disordered and no evidence has been found for the cluster formation of DMF molecules in the liquid state. The experimental result for the weak intermolecular interactions between DMF molecules is supported by ab initio MO-SCF calculations.
108 citations
TL;DR: In this article, a model of the electrical double layer for the nitrobenzene-water interface is presented, in which an ion-free inner layer consisting of laminated monolayers of water and nitron is sandwiched by two diffuse layers on each side of the interface.
Abstract: Electrocapillary curves at the polarized interface between a nitrobenzene solution of tetrabutylammonium tetraphenylborate (TBATPB) and an aqueous solution of lithium chloride at various concentrations of TBATPB and LiCl have been measured by the drop time method using a dropping electrolyte solution electrode at 25 °C. The relative surface excesses of tetrabutylammonium and tetraphenylborate ions in the nitrobenzene phase and of lithium and chloride ions in the aqueous phase were well described by the Gouy-Chapman theory of diffuse layers for both sides of the interface. A model of the electrical double layer for the nitrobenzene–water interface is presented, in which an ion-free inner layer consisting of laminated monolayers of water and nitrobenzene is sandwiched by the two diffuse layers on each side of the interface. The potential difference across the inner layer, which was estimated to be ca. 20 mV at the potential of zero charge, was found to be dependent on the surface charge density and to be ne...
105 citations
TL;DR: In this paper, the axial ligation of [Cob(II)ester]ClO4 with various amines in dichloromethane and toluene was determined by electronic spectroscopy.
Abstract: Heptamethyl cobyrinate perchlorate, [Cob(II)ester]ClO4, was prepared in a good yield from cyanocobalamin. This hydrophobic complex is structurally comparable to the base-off form of vitamin B12r. Thermodynamic parameters (ΔG, ΔH, and ΔS) for axial ligation of [Cob(II)ester]ClO4 with various amines in dichloromethane and toluene were determined by electronic spectroscopy. The isoequilibrium temperatures obtained from plots of ΔH vs. ΔS were 194±20 and 317±20 K in dichloromethane and toluene, respectively. The equilibrium is primarily controlled by entropy at ordinary temperatures and the logK1 value varies sensitively along with the change in pKa of amine in dichloromethane, while the equilibrium values were almost invariant to the choice of amine in toluene because the measurements were carried out near the isoequilibrium temperature. The logK1 value for [Cob(II)ester]ClO4, different from the case of cobalt(II)-porphyrin complexes, depends on the nature of solvent used and undergoes wide variations. The p...
98 citations
TL;DR: In this paper, the atomic distances within a formamide molecule and the intermolecular N···O distance between the hydrogen-bonded molecules are determined by the X-ray diffraction experiment.
Abstract: The molecular and liquid structures of formamide have been studied by means of X-ray diffraction. Relative stabilities of aggregates of formamide molecules have been calculated by using the ab initio LCGO-MO-SCF procedure and minimal basis sets. The atomic distances within a formamide molecule and the intermolecular N···O distance between the hydrogen–bonded molecules are determined by the X-ray diffraction experiment as follows: C=O: 1.24(1) A, C–N: 1.33(1) A, N···O (intramolecular): 2.25(2) A, and N···O (intermolecular): 3.05(5) A. The intermolecular (Remark: Graphics omitted.) bond angle (Θ) is about 120°. It is concluded from the X-ray diffraction experiment that liquid formamide mainly consists of the chain-like hydrogen–bonded structure of formamide molecules by combining through –NH2···O=CH– interactions. The conclusion is supported by the ab initio calculations. Formation of ring-dimers in the liquid formamide has not been confirmed by the X-ray diffraction study, although a possibility of the for...
91 citations
TL;DR: The kinetics and mechanism of the reaction in the photo-excited state of 7-hydroxycoumarin and its derivative have been studied in aqueous solutions by means of measuring the fluorescence spectra and fluorescence lifetime as mentioned in this paper.
Abstract: The kinetics and mechanism of the reaction in the photo-excited state of 7-hydroxycoumarin and its derivative have been studied in aqueous solutions by means of measuring the fluorescence spectra and the fluorescence lifetime. The four fluorescence bands have been identified as emissions from the neutral, anionic, tautomeric, and cationic forms of 7-hydroxycoumarins. The quantitative analysis was performed by using the rate equation which included the term for the direct conversion of the excited neutral molecule to its tautomer in addition to the usual reaction term of dissociation. The rate constants of the tautomerization and dissociation were discussed in detail, and it was revealed that the tautomerization in aqueous solutions was mainly caused by the transfer of a proton between two active sites in the molecule. Such an intramolecular proton-transfer of the coumarins, found first in this paper, is considered to be promoted by water molecules with a hydrogen bond surrounding the excited molecule.
82 citations
TL;DR: In this article, the authors measured the viscosities, apparent molar volumes, and activity coefficients of aqueous solutions for D-glucose, maltose, and maltotriose at various concentrations.
Abstract: Viscosities, apparent molar volumes, and activity coefficients of aqueous solutions for D-glucose, maltose, and maltotriose were measured at various concentrations. The signs of Bst, the increment of viscosity B-coefficient arising from structural change of water, were positive for these three saccharides, and the signs of dB⁄dT, the temperature dependence of B, were negative. The magnetudes of Bst and |dB⁄dT| increased with the number of glucose residue. Activity coefficients were larger than unity and increased with concentration, and their magnitudes also increased with the number of glucose residue. These results indicate that D-glucose, maltose, and maltotriose are structure forming solutes, and that their abilities lie in the order of D-glucose
TL;DR: In this article, the complex-formation constants of dibenzo-24-crown-8 (DB24C8) with alkali metal ions in acetonitrile and the solubility of DB 24C8 in methanol, acetitrile, and propylene carbonate were determined conductometrically and spectrophotically at 25 °C.
Abstract: Complex-formation constants (KML+) of dibenzo-24-crown-8 (DB24C8) with alkali metal ions in acetonitrile and the solubility of DB24C8 in methanol, acetonitrile, and propylene carbonate were determined conductometrically and spectrophotometrically at 25 °C, respectively. The KML+ value sequences of the alkali metal ions with DB24C8 are Na+>Cs+>K+=Rb+. Dibenzo-24-crown-8 shows no remarkable selectivity for the alkali metal ions in acetonitrile. Transfer activity coefficients of the DB24C8 complexes with alkali metal ions were calculated from these data and literature values of transfer activity coefficients of alkali metal ions. For the same alkali metal ion, the bulky DB24C8-alkali metal ion complex is more soluble in the aprotic solvents acetonitrile and propylene carbonate than in the protic solvent methanol as compared with the case of the alkali metal ion itself. The transfer activity coefficient of the DB24C8-alkali metal ion complex from methanol to acetonitrile is somewhat sensitive to the variation...
TL;DR: In this article, three new methods for the preparation of metal colloid in organic solvent are presented: matrix isolation method, gas flow cold trap method and gas flow-solution trap method; the latter was found to give a good colloid solution for the optical measurements.
Abstract: Three new methods for the preparation of metal colloid in organic solvent are presented. These methods were the matrix isolation method, the gas flow-cold trap method and the gas flow–solution trap method; the latter was found to give a good colloid solution for the optical measurements. The metals reported are high purity Ag, Au, Cu, In, Al, Ca, Sn, and Pb. The stability of the colloid is dependent on the kind of metals: Al, In, Au, and Ag are stable, and Pb, Sn, Ca, and Cu are unstable. The optical absorption spectra of these sols were measured in ethanol solution in Ar atmosphere. They are discussed in relation to those reported on the solid matrix or on the solid substrate.
TL;DR: In this article, the concentration dependence of concentration fluctuations at 21, 32, and 42 °C and of Raman spectra at 21 °C were measured for binary solutions of 2-butoxyethanol (BE) and water.
Abstract: The concentration dependence of concentration fluctuations at 21, 32, and 42 °C and of Raman spectra at 21 °C were measured for binary solutions of 2-butoxyethanol (BE) and water. The existence of the two kinds of local structures is inferred; clathrate hydrate-like structure g[(H2O)50BE] and aggregate h[(H2O)4BE]. The compositions of these two structures are the same as those of the two phases into which the solution separates above the critical solution temperature. The phase separation is understood to be the end of the growth of the local structures, which already exist well below the critical solution temperature.
TL;DR: In this article, the authors measured the interface between nitrobenzene solution of tetrabutylammonium tetraphenylborate and aqueous solution of lithium chloride using a dropping electrolyte solution electrode under the precise control of the electrical potential difference and of the ion transfer current across the interface.
Abstract: Electrocapillary curves have been measured of the interface between nitrobenzene solution of tetrabutylammonium tetraphenylborate and aqueous solution of lithium chloride using a dropping electrolyte solution electrode under the precise control of the electrical potential difference and of the ion transfer current across the interface. The nitrobenzene–water interface could be electrically polarized over the voltage span of 300 mV. The residual current was explained as due to both the transfer of tetrabutylammonium ion and tetraphenylborate ion through the interface and the charging current at the interface. The electrocapillary curve was parabolic in shape. The surface charge vs. potential curve derived from the electrocapillary curve agreed with that obtained from the differential capacity vs. potential curve of the interface. The results indicate that the interface can virtually be treated as an ideal polarized interface over a certain potential range.
TL;DR: In this article, the activity coefficients of isomeric monosaccharides, D-glucose, Dmannose, and D-galactose were determined by isopiestic comparison method at 25 °C.
Abstract: Activity coefficients of isomeric monosaccharides, D-glucose, D-mannose, and D-galactose were determined by isopiestic comparison method at 25 °C Excess partial molar entropy of water (\barSwex) of each monosaccharide solution was negative and the absolute value increased with concentration of solute From the magnitudes of negative \barSwex, it was concluded that the structure making ability among three isomers lies in the order D-glucose>D-mannose>D-galactose
TL;DR: The reaction of malonaldehyde under acidic conditions (pH 4.5) with guanosine 5′-monophosphate resulted in the formation of fluorescent 3-(β-D-ribofuranosyl)pyrimido[1,2-a]purin-10(3H)-one5′-phosphate (3a).
Abstract: The reaction of malonaldehyde under acidic conditions (pH 4.5) with guanosine 5′-monophosphate resulted in the formation of fluorescent 3-(β-D-ribofuranosyl)pyrimido[1,2-a]purin-10(3H)-one 5′-phosphate (3a). This adduct was also isolated from malonaldehyde-reacted RNA. The amount of 3a in the modified RNA was estimated to be 0.4 per cent by weight. The fluorescence spectrum of 3a (Ex max. 360 nm, Em max. 500 nm) was similar to that of guanine- and guanosine-malonaldehyde adducts which have the same type base structure. On the other hand, another type of fluorophore (Ex max. 390 nm, Em max. 460 nm) was also formed in the reaction of malonaldehyde with a nucleic acid polymer. Thus, at least two different types of fluorophores are present in malonaldehyde-reacted nucleic acid.
TL;DR: In this paper, the catalysis of (C5Me5)TiCl2/NaC10H8 was extremely high and resulted in the complete isomerization of 1-alkenes in >99% stereoselectivity within a short period.
Abstract: The catalyst systems which consist of MCl2(C5R5)2(M=Ti, Zr; R=H, CH3)/NaC10H8, i-C3H7MgBr, n-C4H9Li or LiAlH4 in 1 : 2 ratio were highly effective for the stereoselective isomerization of monosubstituted 1-alkenes to (E)-2-alkenes. Unconjugated dienes were converted to (E)- or (E,E)-dienes. The catalysis of (C5Me5)TiCl2/NaC10H8 was extremely high and resulted in the complete isomerization of 1-alkenes in >99% stereoselectivity within a short period. The use of the bulky C5Me5 ligand is essential to find out the excellent stereoselectivity. Systems, (C5H5)2TiCl2/NaC10H8 and (C5H5)2TiCl2/i-C3H7MgBr showed less selectivity and the catalysis of the corresponding zirconium systems was very poor irrespective of the reducing agents and substrates.
TL;DR: In this article, the composition of degradation products of polypropylene, especially liquid fraction, formed over silica-alumina and CaX zeolite catalysts was investigated extensively.
Abstract: The composition of degradation products of polypropylene, especially liquid fraction, formed over silica-alumina and CaX zeolite catalysts was investigated extensively. The catalysts gave almost the same product distribution as a function of carbon number at the initial stages of the reaction. The liquid fractions were rich in the same isoalkanes and aromatics as those contained in the gasoline fraction. Most of the isoalkanes were methyl-branched, while the aromatics consisted mainly of those with one or more methyl groups. The catalytic degradations involved extensive aromatization, isomerization and hydrogen transfer as secondary reactions. The difference in catalytic behaviors between silica-alumina and CaX was most remarkable in coke deposition on the catalysts and more deposition on CaX led to greater saturation of the products. The H/C ratio of the products was regarded as a good measure for the degree of coke formation on the catalyst surfaces.
TL;DR: The Raney nickel catalyst was employed as a catalytic electrode in the electrohydrogenation of various unsaturated compounds, including ketones, aromatic aldehydes, Schiff bases, oximes, nitriles, aromatic nitro compounds, olefins, and acetylenes as discussed by the authors.
Abstract: The Raney nickel catalyst was employed as a catalytic electrode in the electrohydrogenation of various unsaturated compounds, including ketones, aromatic aldehydes, Schiff’s bases, oximes, nitriles, aromatic nitro compounds, olefins, and acetylenes. The hydrogen generated electrochemically was adsorbed and activated at the surface of the catalyst; it effectively hydrogenated these compounds, affording products which are very similar to those obtained in a normal catalytic hydrogenation with Raney nickel.
TL;DR: In this article, a p-type semiconductor with a bandgap energy of ca. 2.2 eV and stable during redox reactions was characterized with photoelectrochemical measurements.
Abstract: Polypyrrole films prepared on Pt or SnO2 through electrochemical oxidative polymerization of pyrrole were characterized with respect to electroconductivity by photoelectrochemical measurements. Redox reactions of solution species such as methyl viologen, hydroquinone, oxygen, Cu2+, I−, and Br− occur on these electroconductive films. Light excitation of the film with wavelengths shorter than 550 nm results in observable cathodic photocurrent at the potential region more negative than 0.0 V vs. Ag. The polypyrrole film is a p-type semiconductor with a bandgap energy of ca. 2.2 eV and is stable during redox reactions.
TL;DR: In this paper, potential-step chronoamperometry has been applied to the study of the transfer of the tetramethylammonium (TMA+) ion across the interface between a 0.1 mol dm−3 lithium chloride aqueous solution and a tetrabutyammonium tetraphenylborate nitrobenzene solution.
Abstract: Potential-step chronoamperometry, cyclic voltammetry, and chronopotentiometry have been applied to the study of the transfer of the tetramethylammonium (TMA+) ion across the interface between a 0.1 mol dm−3 lithium chloride aqueous solution and a 0.1 mol dm−3 tetrabutylammonium tetraphenylborate nitrobenzene solution. An analysis of the current-time and current-potential curves obtained by means of potential-step chronoamperometry indicates that the transfer of the TMA+ ion across the water/nitrobenzene interface is a reversible diffusion-controlled process, which can be explained by the theory of the chronoamperometry of a reversible charge transfer at the electrode surface. The values of the diffusion coefficient of the TMA+ ion in the aqueous phase and of the reversible half-wave potential of the TMA+ ion transfer, as determined by means of potential-step chronoamperometry, agreed well with those determined by means of cyclic voltammetry and chronopotentiometry.
TL;DR: An X-ray diffraction study of the title complex has been carried out as discussed by the authors, which has a one-dimensional polymer bridged by chlorine atoms and a carboxyl group like an infinite folding screen.
Abstract: An X-ray diffraction study of the title complex has been carried out. The crystal is orthorhombic, with the space group P212121; Z=4, a=10.021(3), b=13.562(4), c=7.298(3) A. Block-diagonal least-squares refinements have led to the final R value of 0.035. The structure is very similar to that of dichloro(4-hydroxy-L-proline)cadmium(II), which has a one-dimensional polymer bridged by chlorine atoms and a carboxyl group like an infinite folding screen. The thermal behavior is, however, different from that of dichloro(4-hydroxy-L-proline)cadmium(II). The difference is likely to be due to a difference of the crystal structure, whether it contains intermolecular hydrogen bonds or not.
TL;DR: In this paper, cross-linked poly(styrene-divinylbenzene) matrices functionalized with hydrazinosulfonyl groups react with aldehydes and ketones to form the sulfonylhydrazone derivatives.
Abstract: Reins consisting of cross-linked poly(styrene-divinylbenzene) matrices functionalized with hydrazinosulfonyl groups react with aldehydes and ketones to form the sulfonylhydrazone derivatives. The extent of the reaction is sensitive to the type of resin and the bulk of the carbonyl compound. When heated strongly under alkaline conditions, the sulfonylhydrazones release the corresponding alkenes; upon the NaBH4 or LiAlH4 treatment, they also release the corresponding alkanes; and, upon refluxing in methanol with potassium cyanide, they release nitriles containing one additional carbon atom.
TL;DR: In this article, a one-step reaction between diethanolamine or N,N-di[oligo(oxyethylene)]amines and oligoethylene glycol di(p-toluenesulfonates) or corresponding dichlorides in t-butyl alcohol/dioxane in the presence of sodium or potassium tbutoxide is described.
Abstract: Monoaza crown ethers were prepared in satisfactory yields by the one-step reaction between diethanolamine or N,N-di[oligo(oxyethylene)]amines and oligoethylene glycol di(p-toluenesulfonates) or corresponding dichlorides in t-butyl alcohol/dioxane in the presence of sodium or potassium t-butoxide. The reaction conditions in the preparation of monoaza 15- and 18-crown ethers were studied. Various monoaza crown ethers having substituents were also prepared and their properties were investigated.
TL;DR: In this article, the recovery of lithium from geothermal water at Hatchobaru in Kyushu, Japan, was investigated using coprecipitation method using aluminium salts, which achieved an almost complete recovery of Li by the removal of calcium ions and polymerized silica.
Abstract: The recovery of lithium from geothermal water at Hatchobaru in Kyushu, Japan, was investigated. A coprecipitation method using aluminium salts was employed. The lithium concentration in the geothermal water used in the present study was about 10 ppm. To make our experimental results more applicable for geothermal water, a reference lithium solution (10 ppm) was also studied as a control solution. A perfect recovery of lithium was obtained for the reference lithium solution by choosing appropriate conditions. For geothermal water, the yield of Li was not so good as in the control solution. However, an almost complete recovery of lithium was attained for geothermal water by the removal of calcium ions and polymerized silica. The mechanism of Li recovery was also considered.
TL;DR: In this article, a convenient synthesis of optically active S-alkylcysteine, threo-S-Alkyl-β-methylcysteines, and lanthionine derivatives has been investigated.
Abstract: A convenient synthesis of optically active S-alkylcysteine, threo-S-Alkyl-β-methylcysteine, and lanthionine derivatives has been investigated. Benzyl 1-benzyloxycarbonyl-(2S)-2-aziridinecarboxylate and benzyl (2S,3S)-1-benzyloxycarbonyl-3-methyl-2-aziridinecarboxylate, and their enantiomers were treated with several thiols, and the corresponding S-alkylcysteine, threo-S-alkyl-β-methylcysteine, and lanthionine derivatives were prepared via the ring-opening reaction of aziridine in the presence of a catalytic amount of boron trifluoride etherate in good yields.
TL;DR: In this article, a graph-theoretical formula was derived for ring currents induced in a polycyclic conjugated system by a uniform magnetic field, and two advantages of this formula were that ring currents can be evaluated by inspecting a geometry of a conjugation system, and that they can be attributed to the individual π-electron rings.
Abstract: A graph-theoretical formula was derived for ring currents induced in a polycyclic conjugated system by a uniform magnetic field. Two advantages of this formula are that ring currents can be evaluated by inspecting a geometry of a conjugated system, and that they can be attributed to the individual π-electron rings.
TL;DR: In this article, the Pd-catalyzed reaction of aryl halides and triarylphosphonium halides was used to obtain good yields for iodides.
Abstract: Tetraarylphosphonium halides, particularly iodides, can be conveniently prepared by the Pd-catalyzed reaction of aryl halides and triarylphosphines in good yields.
TL;DR: The mode of enantioface-differentiating hydrogenation with asymmetrically modified Raney nickel (MRNi) was investigated by using various sorts of modifying reagents and substrates as discussed by the authors.
Abstract: The mode of enantioface-differentiating hydrogenation with asymmetrically modified Raney nickel (MRNi) was investigated by using various sorts of modifying reagents and substrates. The optical yields (O.Y.) of the hydrogenation of methyl acetoacetate over MRNi for different modifying reagents occured in the following order: (Remark: Graphics omitted.), (Remark: Graphics omitted.). The hydrogenation of various substrates of the structure, (Remark: Graphics omitted.), over tartaric acid-modified Raney nickel (TA–MRNi), gave high optical yields only when the substituent –Y functioned as a good hydrogen bond acceptor like a carbonyl group, and two pairs of hydrogen bondings between substrate and two hydroxyl groups of tartaric acid were available. As for the stereochemistry of the reaction in such a case, (R,R)-TA–MRNi always gave (R)-product in excess. Based on the stereochemistry of the reaction and the role of hydrogen bonds between modifying reagent and substrate, a stereochemical model is proposed to elu...