Development of an efficient method for preparation of 1,3,5-trihydroxyisocyanuric acid (THICA) and its use as aerobic oxidation catalyst

1,3,5-Trihydroxyisocyanuric acid (THICA), which serves as an efficient radical-producing catalyst from hydrocarbons, was successfully prepared by two methods. The reaction of O-benzylhydroxyamine with phenyl chloroformate gave formbenzyloxycarbamic acid phenyl ester of which subsequent treatment with dimethylaminopyridine (DMAP) produced 1,3,5-tribenzyloxyisocyanurate leading to THICA by hydrogenation with H₂ on Pd/C. The other method involved the direct synthesis of 1,3,5-tribenzyloxyisocyanurate from O-benzylhydroxyamine and diphenyl carbonate. The aerobic oxidation of p-methylanisole catalyzed using THICA as a key catalyst afforded p-anisic acid in almost quantitative yield (>99%).     

A regio- and stereoselective alpha-methylation of gamma,delta-epoxy-alpha,beta-unsaturated esters with a Me2Zn-CuCN reagent

A highly regio- and stereoselective alpha-methylation reaction of gamma,delta-epoxy-alpha,beta-unsaturated esters was achieved by using a Me2Zn-CuCN reagent.     

Selective binding of steroids by 2,2'-biquinoline-4,4'-dicarboxamide-bridged bis(beta-cyclodextrin): fluorescence enhancement by guest inclusion

A novel bis(beta-cyclodextrin) was synthesized, and its binding behavior with steroids was investigated to demonstrate that the cooperative co-inclusion of guest and tether by two cyclodextrin moieties is operative to afford the highest molecular selectivity of up to 3.6 for deoxycholate over taurocholate.     

Chelating behavior of new chelating resins derived from n-(o-hydroxybenzyl)iminodiacetic acid

The chelating behavior of a new resin prepared by polycondensation of N-(o-hydroxybenzyl) iminodiacetic acid (o-HDA) with phenol and formaldehyde, is compared with that of the monomer, with p-HDA resin and p-HDA monomer, and with Chelex-100. The order of chelate stability for the o-HDA resin is Cu(II) > Ni(II) > Zn(II) > Co(II). An unusually high stability of the o-HDA and o-HDA resin iron(III) chelates in acidic solution is attributed to the participation of the o-hydroxyl group in the coordination process.     

Di(triptycyl)carbene: a fairly persistent triplet dialkylcarbene

The title carbene was generated and characterized by matrix spectroscopy (ESR and UV/vis) and laser flash photolysis along with theoretical calculations, which revealed interesting effects of triptycyl groups on structure and reactivities of carbenes.     

Supramolecular chirogenesis in zinc porphyrins: equilibria, binding properties, and thermodynamics

Complexation mechanism, binding properties and thermodynamic parameters of supramolecular chirality induction in the achiral host molecule, syn (face-to-face conformation) ethane-bridged bis(zinc porphyrin), upon interaction with chiral monoamine and monoalcohol guests have been studied by means of the UV-vis, CD, (1)H NMR, and ESI MS techniques. It was found that the chirogenesis process includes three major equilibria steps: the first guest ligation to a zinc porphyrin subunit of the host (K(1)), syn to anti conformational switching (K(S)), and further ligation by a second guest molecule to the remaining ligand-free zinc porphyrin subunit (K(2)), thus forming the final bis-ligated species possessing supramolecular chirality. The validity of this equilibria model is confirmed by the excellent match between the calculated and experimentally observed spectral parameters of the bis-ligated species. The second ligation proceeds in a cooperative manner as K(2) > K(1) for all supramolecular systems studied, regardless of the structure of the chiral ligand used. The binding properties are highly dependent on the nature of the functional group (amines are stronger binders than alcohols) and on the structure of the chiral guests (primary and aliphatic amines have overall binding constant values greater than those of secondary and aromatic amines, respectively).     

Succession of stacking disorder in hard-sphere crystal under gravity by Monte Carlo simulation

We have performed Monte Carlo simulations of hard spheres under gravity. Vertical boundaries are hard walls, which are well separated with each other. On the other hand, the periodic boundary condition is imposed in the horizontal direction. While we previously reported enhancement of crystallinity as well as crystallization due to gravity, we present here the results that demonstrate the succession of a defect. In case that the crystal formed at the bottom of the system includes kinds of stacking disorders for the (0 0 1) growth, twin band structure develops as mediated by a stacking disorder succeeded in the crystal formed in the fluid region which lies on the bottom crystal. In case that the stacking structure along horizontal direction changes from the (1 1 1) stacking to the (0 0 1) stacking, twin band structure in the (0 0 1) stacking region develops as succeeded in the crystal transformed. The twin band structure also becomes large with its upward growth.     

Uptake of alkali and alkaline earth metal ions into electrochemically pretreated glassy carbon fibres by flow-through electrolysis

When glassy carbon fibres are used, alkali and alkaline earth metal ions are adsorbed in the micropores which are created or activated by oxidative treatment of the fibres. The average pore radius was estimated to be 2 nm by nitrogen adsorption experiments. Uptake was studied with a flow system consisting of a flow-through carbon-fibre electrode; a dropping mercury electrode at the end of the flow line monitored changes in the metal ion concentrations. The ions were taken up at negative potentials and released at positive potentials. The amount taken up increased in the sequence Na⁺ < Li⁺ < H⁺, suggesting that the ions were desolvated before entering the pore system.     

Polymerization of coordinated monomers VII. A kinetic study on the alternating copolymerization of methyl methacrylate with styrene using stannic chloride

The alternating copolymerization of methyl methacrylate with styrene in the presence of stannic chloride at ?50°C in toluene was kinetically investigated both under photoirradiation and with the tri-n-butylboron-benzoyl peroxide initiator. The concentrations of the binary and ternary molecular complexes in the copolymerization solution were estimated by use of the equilibrium constants. The rates are found to be proportional to the 1.5th and 1.0th orders of the concentration of the ternary molecular complex composed of stannic chloride, methyl methacrylate, and styrene, under photoirradiation and with initiator, respectively. The conversion increases proportionally with the polymerization time, while the degree of polymerization is constant irrespective of the time. The rates depend linearly upon the square root of the intensity of the incident light and upon the concentration of tri-n-butylboron, respectively. The alternating copolymerization is confirmed experimentally to precede the homopolymerization of the monomer charged in large excess both under photoirradiation and with initiator. The kinetic results indicate consistently that the alternating copolymerization proceeds through the homopolymerization of the ternary molecular complex in the steady state with a bimolecular termination. Both the conventional radical mechanism and the double complex mechanism are unsuitable for the present alternating copolymerization.     

Polymerization of coordinated monomers. III. Copolymerization of acrylonitrile–zinc chloride,methacrylonitrile–zinc chloride or methyl methacrylate–zinc chloride complex with styrene

The 1:1 or 2:1 complex of acrylonitrile, methacrylonitrile, or methyl methacrylate with ZnCl₂ was copolymerized with styrene at the temperature of 0–30°C without any initiator. The structure of the copolymer from methyl methacrylate complex and styrene was examined by NMR spectroscopy. The complexes of acrylonitrile or methacrylonitrile with ZnCl₂ gave a copolymer containing about 50 mole-% styrene units. The complexes of methyl methacrylate yielded an alternating copolymer when the feed molar ratio of methyl methacrylate to styrene was small, but with increasing feed molar ratio the resulting copolymer consisted of about 2 moles of methyl methacrylate per mole of styrene. The formation of a charge-transfer complex of styrene with a monomer coordinated to zinc atom was inferred from the ultraviolet spectra. The regulation of the copolymerization was considered to be effected by the charge-transfer complex. The copolymer resulting from the 2:1 methyl methacrylate–zinc chloride complex had no specific tacticity, whereas the copolymer from the 1:1 complex was richer in coisotacticity than in cosyndiotacticity. The change of the composition of the copolymer and its specific tacticity in the polymerization of the methyl methacrylate complex is related to the structure of the complex.