This account reviews transition metal-catalyzed C–C bond formation reactions using alkyl halides, which have rarely been used as carbon sources in conventional transition metal-catalyzed systems. In the reactions, ate complexes formed by the reaction of transition metals with a Grignard reagent play important roles as the active catalytic species. The reactions mentioned here are mechanistically new and provide a promising methodology for the construction of carbon frameworks employing alkyl halides.
A versatile sol–gel method for fabricating porous oxide materials with well-defined co-continuous macropores has been reviewed. The chemical instability, in many cases induced by polymerization of the network-forming components, triggers the formation of biphasic morphologies, followed by an irreversible freezing of the transient morphology by the sol–gel transition of the gelling phase. Upon removal of the non-gelling phase, an oxide framework comprising of controlled macropores can be obtained. The mesopore system of such macroporous materials can be further modified either by a physico-chemical treatment or a supramolecular templating technique. Pure silica and siloxane-based organic–inorganic hybrids with a hierarchical pore system in monolithic form have been successfully applied to the novel type of separation medium for high performance liquid chromatography, HPLC. Additional topics are also described including recent advances in the 3D-analysis of the interfacial properties of macroporous systems, extended compositional variations in the network-forming phase, and emerging applications in areas of biochemistry.
The 4-cyanobutyl group of (4-cyanobutyl)[3,4-lutidine](dimethylglyoximato)[O-(diphenylboryl)dimethylglyoximato]cobalt(III) was isomerized to the 1-cyanobutyl group with retention of the single-crystal form, although the corresponding cobaloxime complex without diphenylboryl in the equatorial ligands did not show such a photoisomerization. The trans–cis–cis conformation of the 4-cyanobutyl group caused by the steric repulsion from the diphenylboryl group is favorable to the crystalline-state reaction. In order to elucidate the detailed isomerization mechanism, two hydrogen atoms of the 4-cyanobutyl group were replaced with the deuterium atoms such as –CH2CH2CH2CD2CN. After the photoisomerization, the crystal structure with deuterated 4-cyanobutyl group was analyzed by neutron diffraction. Only one of the two deuterium atoms of the 4-cyanobutyl group was transferred to the C1 atom such as –CD(CN)CH2CH2CDH2. This result made clear that the photo-produced cyanobutyl radical turned upside down after homolytic cleavage of the Co–C bond, and then the Co(II) atom and the radical made a bond to form the 1-cyanobutyl group.
The densities (ρ) and ultrasonic speeds (u) of pure dimethyl sulfoxide (DMSO), benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene, and those of their binary mixtures, with DMSO as the common component, over the whole composition range have been measured at 298.15, 303.15, 308.15, 313.15, and 318.15 K. The excess molar volume (VE), deviation in isentropic compressibility (Δks), apparent molar volume (Vφ,2), apparent molar compressibility (Kφ,2), partial molar volume (), and partial molar compressibility () of aromatic hydrocarbons in DMSO at infinite dilution have been calculated from the experimental data. The variation of these parameters with the composition and temperature of the mixtures indicates that the interaction (DMSO–aromatic hydrocarbons) follows the order: benzene > toluene > p-xylene > m-xylene > o-xylene > mesitylene. The effect of the number and position of the methyl groups in these aromatic hydrocarbons on molecular interactions in these mixtures is also discussed. The VE values have also been calculated theoretically by using Flory’s statistical theory and the Prigogine–Flory–Patterson theory. The calculated VE values were found to be in good agreement with the experimental VE values for most of the mixtures.
Intercalation of proton-type layered titanium(IV) oxides, H2Ti5O11·xH2O (H-TiO2(A)) and H0.7Ti1.825O4·xH2O (H-TiO2(B)), with n-alkylamines were examined for carbon numbers nc = 3–18 in a benzene solution. The amount of intercalated n-alkylamines was about 1 mol per 1 mol of H-TiO2(A) and well-defined X-ray diffraction patterns were observed for nc = 4–14, reflecting the formation of a n-alkylamine bilayer between the layered lamellae. The alkyl chain in the bilayer was found to incline 66° against the basal plane. For nc = 3, a fluffy suspended colloid appeared in the reactant solution and the amount of intercalated amines was about 2 mol per 1 mol of H-TiO2(A), and weak X-ray diffraction peaks suggested the exfoliation and formation of the monolayer or several multilayer sheet of H-TiO2(A). The size of the exfoliated colloid particles was examined using dynamic light scattering photometry. The scatter angle dependence suggested the shape of the colloid particles was a thin lamella and the average radius was estimated to be about 80 and 210 nm for propylamine and tetrabutylammonium hydroxide intercalation compounds prepared in aqueous solution, respectively. The shape of the colloid particles was rather isotropic and the radius was about 1.0 μm for a propylamine intercalation compound prepared in a benzene solution. The result of dynamic light scattering seems consistent with the exfoliation and following coagulation of layered lamellae of H-TiO2(A).
Beryllium(II), chromium(III), manganese(II), iron(III), cobalt(II), nickel(II), copper(II), zinc(II), arsenic(V), selenium(IV), cadmium(II), antimony(III), and lead(II) ions in concentrated salt solutions, such as seawater or sodium chloride and sulfate solutions, were collected quantitatively by coprecipitation with hydroxides of ytterbium(III), gallium(III), and magnesium(II). In this method, a rapid coprecipitation technique combined with internal standardization was applied to simplify the operation; yttrium was used as an internal standard. The 13 elements collected were readily determined by inductively coupled plasma atomic emission spectrometry using internal standardization. The detection limits (3σ, n = 10) were in the range of 0.003 μg (for beryllium(II)) to 0.13 μg (for zinc(II)) in the initial sample solution (up to 150 mL). The proposed method was applied to the analyses of some commercially available salts and an effluent as well as the certified reference materials; the elements ranging from 0.03–0.14 μg g−1 in the salts, 0.004–0.041 mg L−1 in the effluent, or 0.006–0.30 mg L−1 in the certified reference materials could be determined with the relative standard deviation of 7–33, 0.3–3, or 2–17%, respectively. The time required for the preconcentration was approximately 20 min.
Four kinds of tris(β-diketonato)europium(III) complexes were demonstrated to form highly coordinated complexes with inorganic anions and to exhibit anion-dependent luminescence. Their luminescence profiles were significantly dependent on the natures of β-diketonato ligands and external coordinative anions: Tris[3-(heptafluorobutyryl)-2-bornanonato]europium(III) complex gave F− anion-enhanced luminescence, and tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadionato)europium(III) complex responded to HSO4− and CH3CO2− anions. Although the employed europium complexes included similar β-diketonato ligands, UV and IR characterizations and luminescence lifetime measurements revealed that the structure of the β-diketonato ligand had significant influences on anion coordination and sensing behaviors of the europium complex. Since the observed anion-enhanced luminescence was high enough to be detected by the naked eye, visual detection of the F− anion in an aqueous sample was realized with the tris[3-(heptafluorobutyryl)-2-bornanonato]europium(III) complex.
Particulate and gaseous organics are formed, as transient products, from dilute concentrations of xylene in air under electron beam irradiation; however, the components of the particulate organic products and the particle formation process are unknown. In the present study, the component analysis of particulate products were performed employing an atmospheric pressure ionization mass spectrometer (APIMS) based on a temperature-programmed desorption method to identify the components of the particles from o-xylene as a function of their gasification temperatures. Ions of 139–203 u with a peak interval of the m/z of 16 u, the same as the value of O+, were observed as vaporized particle components at correspondent temperatures. The ions of 43, 47, 61, 97, 111, 135, and 139 u were detected as the vaporized components at 333 K. The ions of 155, 171, and 187 u were observed at 363 K, besides that of 203 u at 393 K. The ions of 392–421 u were also appreciable with peak heights of 10−2 order lower than those for the ions of 139–203 u at temperatures higher than 393 K. The gaseous products in irradiated o-xylene/air mixtures were also analyzed with the APIMS. The ions with m/z lower than 139 u were detected as gaseous products.
Three supramolecular isomers of an Fe–NCS complex and two isomers of an Fe–NCSe complex bridged by 1,2-di(4-pyridyl)ethane have been obtained. 57Fe Mössbauer spectroscopy revealed a drastic change in the QS value by changing the structure and by changing NCS to NCSe. Solid-to-solid transformation was observed, accompanied by a drastic change in the QS value.
A ruthenium–dioxolene–amine complex, [RuIII(NH2-L)(Bu2sq)](PF6)2·0.5H2O (NH2-L = bis(2-pyridylmethyl)-2-aminoethylamine, Bu2sq− = 3,5-di-tert-butylsemiquinonate), was newly prepared. The complex undergoes spontaneous one-electron reduction under basic conditions in MeOH and works as an electrocatalyst in the oxidation of benzyl alcohol to benzaldehyde under electrolysis at +0.4 V (vs SCE).
Cetyltrimethylammonium chloride was sorbed on silica gels and formed stable admicelles at pH 9. The extractabilities of chlorophenols were greater than those to sodium dodecyl sulfate–γ-alumina admicelles. Because the admicelles were floatable, the flotation was found to be useful for the rapid and efficient recovery of admicelles.
In a 50 vol % sulfolane–H2O mixed solvent, extensive studies have been carried out of the concentrated salt effects on the solvolysis reaction rates of aliphatic halides and related compounds (RX). In the solvent system, the “pseudo” first-order rate constants (k/s−1) of typical SN1 substrates, 1-adamantyl chloride and bromide, or 2-adamantyl bromide, were increased exponentially by the addition of MClO4 (M = Li and Na) and M(ClO4)2 (M = Mg and Ba); the extent of the cation effects increased as Na+ < Li+ < Mg2+ ≈ Ba2+, which was attributed to the “chemical” interaction between the metal ions and the leaving-group anions in the “aqueous” solution modified by the mixed-organic solvents and concentrated salts. Based on the Raman spectra, we discuss the distortion of the bulk water structure and the alteration of properties of water into those of a “non-aqueous” solvent with the addition of the organic solvents and concentrated salts (LiClO4 and Et4NBr) as well as with increasing temperature. However, the addition of non-metallic salts, i.e., Et4NX (X− = ClO4−, Cl−, Br−, and tosylate), caused decreases in the rates substantially, regardless of the leaving group (Cl or Br): the deceleration effects increasing as ClO4− < Br− < Cl− < TsO−. The deceleration in the solvolysis rates with Et4NX and R4NBr (R = Pr and n-Bu) should be caused by mainly the further decrease in water activity of the solvents. In addition, we would like to report solvolyses accompanied by “ion exchange” reactions for the typical SN2 substrates, hexyl chloride, bromide, and tosylate, in the sulfolane–H2O solvent.
An efficient method for the N-arylation of pyridin-2(1H)-ones and the related heteroaromatic lactams has been established via ligand-coupling reactions using tri- or tetra-aryl organobismuth(V) reagents such as triarylbismuth dichlorides. Also, N-alkenylation of pyridin-2(1H)-one was achieved similarly by using alkenyltriarylbismuth(V) reagents.
Stereoselective synthesis of both optically active cis- and trans-1-amino-2-hydroxycyclohexane-1-carboxylic acids (Ahhs) 1a and 1b was accomplished by an asymmetric version of the Strecker synthesis. Stereochemical aspects of their chiral induction processes are investigated.
The reactivity of 8-iodoimidazo[1,2-a]pyridine towards copper- and palladium-catalyzed aminations is reported. The copper-based methodology led to the attempted coupling products in only poor yields due to difficult purifications. On the contrary, good coupling yields were obtained using palladium-catalyzed amination protocols. The superiority of Pd2dba3 was demonstrated over Pd(OAc)2.
Oxidation–reduction condensation between 2-sulfanyl-1,3-benzothiazole (Btz-SH) and the alkyl diphenylphosphinites 1, prepared from tertiary alcohols, proceeded smoothly in the presence of 2,6-di-t-butyl-1,4-benzoquinone (DBBQ) and the corresponding S-alkylated products 2 were afforded in good yields. The stereo-inverted chiral Btz sulfides 2 were also produced stereospecifically by this condensation that used 1 derived from chiral tertiary alcohols. Subsequent removal of the Btz groups of 2 with t-BuLi or LiAlH4 provided a new synthetic route to chiral tertiary thiols and the structurally-related dialkyl sulfides.
A tweezer-type cavitand bearing highly coordinated hydrosilane units at the pincer moieties was synthesized and its crystal structure was elucidated. It was found that the cavitand molecules and the hexane molecules included in their cavities form a unique shuttlecock-like columnar arrangement in the crystalline state.
Enantiomers of the title intramolecular amine–borane complex with a B-pentafluoropropionyloxy ligand were resolved by chiral HPLC. X-ray analysis of the (+)-isomer revealed that the configuration of the chiral boron center was S by the Bijvoet method. Thus, the absolute configuration of this chiral borane compound was established as (S)-(+) or (R)-(−).
Some pyrazine dyes based on the same chromophoric system with different steric nature were synthesized to evaluate the correlation between solid-state fluorescence and molecular arrangement. It was confirmed that the solid-state fluorescence is significantly correlated with the prevention of complete stacking between chromophoric systems in the crystalline state. This result suggests that the introduction of bulky substituents to fluorescent dyes should be made on substantial positions for preventing the complete stacking between the chromophoric systems on the basis of the crystal structure.
A HZSM-5-supported palladium catalyst, which was prepared by the conventional impregnation method, was utilized in amidocarbonylation reactions. Several important parameters were optimized to give moderate to excellent yields. The catalyst recycling of Pd/HZSM-5, for the first time, was achieved for at least four run times without depreciation of catalytic activity. The studies of TEM images revealed that agglomeration of the palladium species of Pd/HZSM-5 catalyst was avoided after reaction, which was quite different from the case of Pd/C catalyst.