Yoshinobu Sugie

Bio: Yoshinobu Sugie is an academic researcher from Seikei University. The author has contributed to research in topics: Isopropyl alcohol & Reagent. The author has an hindex of 2, co-authored 2 publications receiving 72 citations.

Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C-H Bonds Elaboration

Abstract: Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration of aliphatic C-H bonds. In this manifold, a photocatalyst (PCHAT) exploits the energy of a photon to trigger the homolytic cleavage of such bonds in organic compounds. Selective C-H bond elaboration may be achieved by a judicious choice of the hydrogen abstractor (key parameters are the electronic character and the molecular structure), as well as reaction additives. Different are the classes of PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, a metal-oxo porphyrin and a tris(amino)cyclopropenium radical dication. The processes (mainly C-C bond formation) are in most cases carried out under mild conditions with the help of visible light. The aim of this review is to offer a comprehensive survey of the synthetic applications of photocatalyzed d-HAT.

Site-Selective C–H Functionalization by Decatungstate Anion Photocatalysis: Synergistic Control by Polar and Steric Effects Expands the Reaction Scope

Abstract: The synergistic control of the SH2 transition states of hydrogen abstraction by polar and steric effects provides a promising strategy in achieving site-selective C(sp3)–H functionalization under decatungstate anion photocatalysis. By using this photocatalytic approach, the C–H bonds of alkanes, alcohols, ethers, ketones, amides, esters, nitriles, and pyridylalkanes were functionalized site-selectively. In the remarkable case of a 2,4-disubstituted cyclohexanone bearing five methyl, five methylene, and three methine C–H bonds, one methine C–H bond in the isoamyl tether was selectively functionalized.

Acid catalysts prepared by impregnation of tungstophosphoric acid solutions on different supports

Abstract: Tungstophosphoric acid (TPA) in 50% v/v ethanol–water solutions was used to impregnate carbon, TiO2, SiO2 and γ-Al2O3 (Spheralite and Akzo) at 20°C. The solutions were characterized by UV-visible and nuclear magnetic resonance spectroscopies and the results indicated that the main species present was the undegraded anion of the acid both before and after the contact with carbon, TiO2, SiO2 and γ-Al2O3 Akzo. However, the nuclear magnetic resonance spectrum of the solution in contact with γ-Al2O3 Spheralite allowed to observe a tungstodiphosphate anion. X-ray diffraction of the impregnated solids dried at 70°C showed the same diffraction patterns as the supports, possibly owing to a high dispersion of non-crystalline species. The Fourier transform infrared and nuclear magnetic resonance spectroscopies of carbon, TiO2 and SiO2 impregnated with TPA showed that the species present was the undegraded [PW12O40]3− anion. When using carbon and TiO2, the supported acid was thermally stable up to 425°C, similarly to the bulk acid, whereas on SiO2 support, the anion underwent partial degradation from 365°C onwards. In TPA-impregnated γ-Al2O3 samples dried at 70°C, diffuse reflectance and nuclear magnetic resonance spectroscopies allowed us to observe a partial degradation of the anion, the extent of which was not appreciably increased by the subsequent calcination. The specific activity of the catalysts in the isopropanol dehydration reaction showed that TPA supported on carbon, TiO2 and SiO2 present higher acidity than the bulk acid, unlike in alumina where the partially degraded species gave a lower acidity.

Photocatalytic degradation of aqueous 4-chlorophenol by silica-immobilized polyoxometalates

Abstract: The degradation of 4-chlorophenol with near-UV light by silica-immobilized polyoxometalate (POM-in-SiO2) catalysts has been studied. The silica-immobilized Na6W7O24 (SW7), H4W1032 (SW10), H3PW12O40 (SPW12), and H6P2W18O62 (SP2W18) were prepared by means of the sol-gel hydrothermal technique through the hydrolysis of tetraethoxysilane in aqueous solution of the corresponding polyoxometalate, respectively. The degradation of 4-chlorophenol was monitored by measuring Cl- and CO2 concentrations and analyzing reaction intermediates by GC/MS analysis. During irradiation, 4-chlorophenol first dechlorinated to form hydroquinone and p-benzoquinone, and then these intermediates further mineralized to form CO2 and H2O. The degree to which 4-chlorophenol was mineralized by photocatalytic oxidation was investigated. Results indicate less than 15% for SW7 but nearly complete mineralization for SW10 after 60 min of photoirradiation. The present studies suggest that POM-in-SiO2 catalysts may be a novel type of photocatalyts for the purification of the environmentally chlorophenol-contaminated water.