Highly Selective Asymmetric Intramolecular Selenocyclisation

Asymmetric intramolecular selenocyclisation of alkenoic acids, alkenols and alkenyl urethanes using chiral ferrocenylselenenyl cations proceeds smoothly to give the corresponding lactones, cyclic ethers and N-heterocyclic compounds, respectively, in moderate yields with very high diastereoselectivities.     

Chiral Bis(oxazoline)-copper Catalyzed Enantioselective Imidation of Sulfides

Prochiral sulfides reacted with Phl=NTs in the presence of a catalytic amount of Cu(I) salt together with a chiral 4,4′-disubstituted bis(oxazoline) ligand to afford the corresponding chiral sulfimides.     

Combustion behaviors of isolated n-decane and ethanol droplets in carbon dioxide-rich ambience under microgravity

The burning and sooting behaviors of isolated fuel droplets for ethanol and n-decane are examined in high concentration of the ambient carbon dioxide under microgravity. A quartz fiber with the diameter of 50 μm maintains the droplet in the center of the combustion chamber and the range in the initial droplet diameter is from 0.30 to 0.80 mm. The ambience consists of oxygen, nitrogen and carbon dioxide. The concentration of oxygen is 21% in volume, and that of carbon dioxide is varied from 0% to 60% in volume. Detail measurements of the projected image of the droplet are conducted by using a high speed video camera and the effective droplet diameter squared are calculated from the surface area of the rotating body of the projected object. From evolutions of the droplet diameter squared, the instantaneous burning rates are calculated. Time history of the instantaneous burning rate clearly represents the droplet combustion events, such as the initial thermal expansion, ignition and following combustion. The instantaneous burning rate for n-decane shows an increasing trend during combustion, while that for non-sooting ethanol remains almost constant or shows a decreasing trend. A slight stepwise increase in the instantaneous burning rate is observed for larger n-decane droplets in air, which may be attributed to soot accumulation. However, this behavior of the burning rate disappears in higher concentration of carbon dioxide. Direct observation of the droplet flame indicates suppression of soot production in higher concentration of carbon dioxide and the suppression is enhanced for smaller droplet.     

Vinyl Polymerization by Metal Complexes. XXXIII. Polymerization of Acrylonitrile Initiated by Triazole-Copper(II) Complex in Dimethylsulfoxide Solution

Polymerization of acrylonitrile initiated by triazole-copper(II) complexes was studied in dimethylsulfoxide solution. It was found that the polymerization proceeds by a free radical mechanism; however, the complexes can hardly homopolymerize methyl methacrylate and styrene. Ability of the complexes to initiate polymerization seems to depend on the substituents of triazole, the sort of solvents, and the counterions of copper(n) salts. From the data of visible spectroscopy and the spin trapping, the initiation mechanism was discussed in terms of reduction of copper(II) followed by forming active species.     

Vinyl Polymerization by Metal Complexes. XXXII. Formation of Glycolchitosan-Copper(II) Complex and the Initiation of Vinyl Polymerization by Using the Complex

The formation of the water-soluble glycolchitosan-copper (II) complex was studied by ultraviolet and visible spectroscopy and by viscosity measurement. The structure of the polymer complex in question was found to change with pH value of the system. The glycolchitosan-copper (II) complex was active as a free-radical initiator for the polymerization of methyl methacrylate and acrylonitrile in the presence of carbon tetra- chloride. The maximum conversion was observed at neutral pH, and was influenced by the presence of neutral salts. Relation- ship between the activity of the polymer complex for initiating the polymerization and its structure was discussed.     

Vinyl Polymerization by Metal Complexes. XXIII. UV and Kinetic Studies on the Photopolymerization with Iron(III)-Amine-Carbon Tetrachloride Systems

Abstract

In order to elucidate the initiation reaction of the photopolymerization with iron(III)-amine-carbon tetrachloride systems, the photochemical reaction process among iron(III), amine, and carbon tetrachloride in methanol solution was followed at 0°C by UV spectroscopy as for iron(III) ion. The rate constants of both the reduction of iron (III) under irradiation with light and the oxidation of iron(II) in the dark were measured, and were related to the rates of photopolymerization of methyl methacrylate. Kinetic study on the photopolymerization of methyl methacrylate with iron(III)-triethylenetetramine-carbon tetrachloride system was made in parallel in methanol solution at 0°C. The initiation mechanism of the photopolymerization was postulated.     

Vinyl Polymerization by Metal Complexes. VII

Abstract

The photopolymerization of vinyl monomers by metal salt-saccharide system was investigated in various solvents. The rate of polymerization in the presence of a iron(III) salt in aqueous media was remarkably accelerated by the addition of saccharides. The acceleration caused by a series of saccharides was found to be in the following order: glucose > fructose > lactose maltose. α-Methyl-d-glucoside and sucrose exhibited very little effect. The overall activation energy for the photopolymerization of acrylonitrile in the presence of glucose was found to be 2.7 kcal/mole, about half of the value obtained in the absence of glucose.     

Tris(porphyrinyl-oxinato)Ga Complexes as a Photosynthetic Antenna Miniature

Two oxinylporphyrins, 5-(8-hydroxy-5-quinolinyl)-10,15,20-( p -tolyl)- porphyrin ( 1 ) and 5,15-bis(8-hydroxy-5-quinolinyl)-10,20-bis( n -heptyl)-porphyrin ( 2 ), were prepared and coordinated with Ga(III) to afford tris(oxinato) complex 3 and poly(oxinato) complex 4 , respectively. The structure of 3 was analyzed by variable temperature NMR study with referring to tris(8-hydroxy-5-quinolinyl)Ga(III) complex 5 to be in a meridional form. Oxinato ligands of 3 and 5 were exchanged with one another, with keeping the meridional structure. UV-Vis and fluorescence spectra of tris(oxinato)complex 3 and poly(oxinato)complex 4 were compared with each monomeric compound 1 and 2 . The absorption spectra showed only a slight broadening of the Soret band, suggesting trivial electronic and excitonic interactions. The fluorescence intensity was increased significantly compared with each monomeric compound 1 and 2 . At the same time, efficient excitation energy transfer among three porphyrins has been observed.