Palladium-catalyzed direct coupling reaction of propargylic alcohols with arylboronic acids

The direct coupling of propargylic alcohols with arylboronic acids has been achieved using palladium catalyst. Various propargylic alcohols and arylboronic acids can be coupled to afford the corresponding allenic and propargylic arenes, which are selectively produced depending on the substituent on the propargylic alcohol, respectively.     

Asymmetric induction copolymerization. Cationic copolymerization of l-menthyl vinyl ether with indene and acenaphthylene

l-Menthyl vinyl ether (l-MVE) was homopolymerized and copolymerized with the monomers indene (IN) and acenaphthylene (ANp) by BF₃OEt₂ as a catalyst. The chiral menthyl substituent was cloven from the homopolymers and copolymers using dry-hydrogen bromide gas. After the removal of optically active menthyl group, poly(vinyl alcohol) (PVA) from l-MVE homopolymer was optically inactive, and copolymers (VA-IN, VA-ANp) from l-MVE-IN and l-MVE-ANp copolymers were still optically active. Hence, in the case of l-MVE homopolymer, it was concluded that asymmetric induction in the polymer main chain can only produce pseudoasymmetry. In the case of l-MVE-IN and l-MVE-ANp copolymers, it was found that asymmetric induction proceeded in the copolymer main chain and was caused by the influence of chiral menthyl group.     

Asymmetric induction radical copolymerization of optically active l-menthyl vinyl ether with vinylene carbonate and indene

The copolymerizations of l-menthyl vinyl ether (l-MVE) with the monomers vinylene carbonate (VCA) and indene (IN) were carried out in benzene with azobisisobutyronitrile (AIBN) as an initiator to obtain optically active copolymers. The optically active l-menthyl residue from the copolymer main chain was removed using dry hydrogen bromide gas. After the ether cleavage reaction, the copolymers prepared (VA–VCA and VA–IN) were still optically active, and hence it was found that asymmetric induction had taken place in the copolymer main chain. The optical rotatory dispersion (ORD) and circular dichroism (CD) data of the original and ether-cloven copolymers were also determined.     

Recent progress of high-power negative ion beam development for fusion plasma heating

A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D⁻ ion beam. In the preliminary experiment using one ion source, a D⁻ ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D⁻ beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/I_D⁻ < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H⁻ ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator.     

Polymerizability of unsaturated monomers capable of forming stable radicals

Some unsaturated monomers bearing hindered phenol and arylamine groups capable of forming stable radicals were prepared. Radical polymerizations of vinyl monomers having such groups were investigated with the use of azobisisobutyronitrile, benzoyl peroxide, cumene hydroperoxide, and tetraethylthiuram disulfide as initiator. Polymerizations of these monomers went normally only when azobisisobutyronitrile was used as initiator. The other initiators inhibited polymerizations remarkably or completely. The results suggest that radicals resulting from benzoyl peroxide and cumene hydroperoxide or tetraethylthiuram disulfide abstract hydrogen of the phenol or the amine to produce the stable radicals, thereby inhibiting the polymerization. Meanwhile, carbon radicals resulting from azobisisobutyronitrile add selectively to the vinyl double bonds of the monomers to initiate the polymerizations. The vinyl derivatives as well as allyl derivatives and cinnamic acid derivatives copolymerize easily with conventional monomers such as styrene, maleic anhydride, and butadiene, again, only when azobisisobutyronitrile was used as initiator. Antioxidative properties for styrene copolymers and butadiene-styrene copolymers incorporating the hindered phenol monomers were investigated.     

Liquid crystalline gel with refractive index gradient of curdlan

Curdlan dissolved in aqueous sodium hydroxide was dialyzed to aqueous calcium chloride to form a gel. Transparent and turbid concentric layers observed in the gel cross section perpendicular to the long axis of the dialysis tube were identified as liquid crystalline gels with refractive index gradient and amorphous gels, respectively. The thickness of each layer was proportional to the diameter of the dialysis tube, and the gelation proceeded in proportion to the root of time. The unique pattern formation was attributed to the change of curdlan conformation and calcium-induced cross-linking resulting from a diffusion of calcium cations and hydroxide anions through the dialysis tube. It is suggested that the orderedness of the curdlan molecules decreases by the increase of the curvature of the concentric liquid crystal layers as the layer comes toward the center of the dialysis tube.     

Singlet Oxygen–mediated Hydroxyl Radical Production in the Presence of Phenols: Whether DMPO–·OH Formation Really Indicates Production of ·OH?¶

The reaction of singlet oxygen (1O2) generated by ultraviolet-A (UVA)-visible light (lambda > 330 nm) irradiation of air-saturated solutions of hematoporphyrin with phenolic compounds in the presence of a spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), gave an electron spin resonance (ESR) spectrum characteristic of the DMPO-hydroxyl radical spin adduct (DMPO-*OH). In contrast, the ESR signal of 5,5-dimethyl-2-pyrrolidone-N-oxyl, an oxidative product of DMPO, was observed in the absence of phenolic compounds. The ESR signal of DMPO-*OH decreased in the presence of either a *OH scavenger or a quencher of *O2 and under anaerobic conditions, whereas it increased depending on the concentration of DMPO. These results indicate both 1O2- and DMPO-mediated formation of free *OH during the reaction. When DMPO was replaced with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), no DEPMPO adduct of oxygen radical species was obtained. This suggests that 1O2, as an oxidizing agent, reacts little with DEPMPO, in which a strong electron-withdrawing phosphoryl group increases the oxidation potential of DEPMPO compared with DMPO. A linear correlation between the amounts of DMPO-*OH generated and the oxidation potentials of phenolic compounds was observed, suggesting that the electron-donating properties of phenolic compounds contribute to the appearance of *OH. These observations indicate that 1O2 reacts first with DMPO, and the resulting DMPO-1O2 intermediate is immediately decomposed/reduced to give *OH. Phenolic compounds would participate in this reaction as electron donors but would not contribute to the direct conversion of 1O2 to *OH. Furthermore, DEPMPO did not cause the spin-trapping agent-mediated generation of *OH like DMPO did.