Yukihiro Ohsugi

Bio: Yukihiro Ohsugi is an academic researcher from Kyoto University. The author has contributed to research in topics: Ruthenium & Allylic rearrangement. The author has an hindex of 4, co-authored 4 publications receiving 601 citations.

Ruthenium-catalyzed N-alkylation and N-benzylation of aminoarenes with alcohols

Abstract: Des aminoarenes sont transformes directement en amines secondaires et tertiaires par reaction a 150-180°C avec des alcools primaires en presence de catalyseurs complexes de Ru dont le plus actif est le dichloro-tris(triphenylphosphine)-Ru. Cinetique. On propose un cycle catalytique qui met en jeu une attaque nucleophile de l'aminoarene sur un aldehyde intermediaire

The ruthenium complex catalyzed N-heterocyclization of aminoarenes to quinoline derivatives using allylic alcohols and aliphatic aldehydes.

Abstract: Aminoarenes reacted with 2-propen-1-ol and 2-buten-1-ol at 180 °C to give quinoline derivatives in fairly good yields in the presence of a catalytic amount of a ruthenium complex. Dichlorotris(trip...

[A Study of Longitudinal NPS Measurement in CT Images Based on the Central Cross-section Theorem].

Abstract: PURPOSE Various approaches in noise power spectrum (NPS) analysis are currently used for measuring a patient's longitudinal (z-direction) NPS from three-dimensional (3D) CT volume data. The purpose of this study was to clarify the relationship between those NPSs and 3D-NPS based on the central slice theorem. METHODS We defined the 3D-NPS(fx, fy, fz) that was calculated by 3D Fourier transform (FT) from 3D noise data (3D-Noise(x, y, z), x-y scan plane). Here, fx, fy and fz are spatial frequencies corresponding to the axes of x, y and z, respectively. Based on the central slice theorem, we described three relationships as follows. (1) The fz-directional NPS calculated from the 3D-Noise(x=0, y=0, z) is equal to the profile obtained by projecting 3D-NPS(fx, fy, fz) in fx- and fy-directions. (2) The fz-directional NPS calculated from the profile obtained by projecting 3D-Noise(x=0, y, z) in the y-direction is equal to the profile at fy=0 in the data obtained by projecting 3D-NPS(fx, fy, fz) in the fx-direction. (3) The fz-directional NPS calculated from the profile obtained by projecting 3D-Noise(x, y, z) in x and y-directions is equal to the profile of 3D-NPS(fx=0, fy=0, fz). To verify them, we compared the NPSs measured from actual 3D noise data that were obtained using a cylindrical water phantom. RESULTS In each relationship (1)-(3), the fz-directional NPS matched the profile obtained from the 3D-NPS(fx, fy, fz). CONCLUSION Based on the central slice theorem, we clarified the relationships between fz-directional NPSs and 3D-NPS. We should understand them and then consider which method should be used for fz-directional NPS measurement.

Direct Synthesis of Amides from Alcohols and Amines with Liberation of H2

Abstract: Given the widespread importance of amides in biochemical and chemical systems, an efficient synthesis that avoids wasteful use of stoichiometric coupling reagents or corrosive acidic and basic media is highly desirable. We report a reaction in which primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen (the only products) in high yields and high turnover numbers. This reaction is catalyzed by a ruthenium complex based on a dearomatized PNN-type ligand [where PNN is 2-(di-tert-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine], and no base or acid promoters are required. Use of primary diamines in the reaction leads to bis-amides, whereas with a mixed primary-secondary amine substrate, chemoselective acylation of the primary amine group takes place. The proposed mechanism involves dehydrogenation of hemiaminal intermediates formed by the reaction of an aldehyde intermediate with the amine.

Applications of acceptorless dehydrogenation and related transformations in chemical synthesis.

Abstract: Conventional oxidations of organic compounds formally transfer hydrogen atoms from the substrate to an acceptor molecule such as oxygen, a metal oxide, or a sacrificial olefin. In acceptorless dehydrogenation (AD) reactions, catalytic scission of C-H, N-H, and/or O-H bonds liberates hydrogen gas with no need for a stoichiometric oxidant, thereby providing efficient, nonpolluting activation of substrates. In addition, the hydrogen gas is valuable in itself as a high-energy, clean fuel. Here, we review AD reactions selectively catalyzed by transition metal complexes, as well as related transformations that rely on intermediates derived from reversible dehydrogenation. We delineate the methodologies evolving from this recent concept and highlight the effect of these reactions on chemical synthesis.