Kohei Sekine 교수

Often stoichiometric amounts of gold find use in materials science; occasionally gold is even used as a support. This review discusses the contributions of gold catalysis, both homogeneous and heterogeneous, to the field of materials science. One topic is the synthesis of polymers, including nanowires and polyesters, the postcyclization of polymers, polymerization by cyclopropanation, and gold-catalyzed radical polymerization reactions. Other topics are dyes, phosphonium salts, and a wide range

The silver-catalyzed three-component reaction of propargylic amines, carbon dioxide, and N-iodosuccinimide for the stereoselective synthesis of (E)-iodovinyloxazolidinones was developed. The silver-catalytic system could be applied to various propargylic amines to afford the corresponding iodovinyloxazolidinones in high yields. The structure of the oxazolidinone was confirmed by X-ray structure analysis to be the E-isomer for the geometry of the exo-olefin. The silver-catalyzed cyclization and r

The gold-catalyzed facile synthesis of U-shaped and S-shaped bispentalenes is described from easily available tetra(arylethynyl)-benzenes and -naphthalenes. The optoelectronic and transistor properties were also investigated. The selectivity between the U-shaped and S-shaped bispentalene isomers can be tuned by the bulkiness of the ligand and the substrates. The S-shaped naphthalene-based bispentalene shows a one-dimensional face-to-face packing pattern in solid state and a good hole mobility, i

C-C bond-forming carboxylation and cyclization of trimethyl(2-methylenebut-3-yn-1-yl)silane derivatives and carbon dioxide was developed. Silver catalysts and CsF promoted the reaction to afford the corresponding 2-furanone and 2-pyrone derivatives in good-to-high yields. The structure of the 2-furanone was confirmed by single-crystal X-ray crystallography, which revealed that the geometry of the exo-olefin was that of a Z-isomer. When an aromatic ring-substituted alkyne was used, 2-furanone der

The gold-catalyzed annulation of diethynyl N-heterocycles for the synthesis of quinoxaline-/phenazine-based pentalenes and the study of their optoelectronic properties are described. The inhibition of the gold catalyst by the nitrogen centers in the substrate and the product could be overcome by increasing the reaction temperature to 130 °C, which usually leads to catalyst decomposition in gold catalysis. At 130 °C, 6,7-di(arylethynyl)quinoxalines in chlorobenzene give the corresponding pentalen

We have developed the divergent deaminative borylation and hydrodeamination of primary aromatic amines using bis(pinacolato)diboron. These transformations can be switched by the reaction conditions. Mechanistic and computational studies have suggested that the cleavage of the C-N bond and the formation of C-B bond are unlikely to involve free aryl radical intermediates. However, hydrodeamination is shown to proceed via hydrogen atom transfer between the corresponding aryl radical and an ethereal

Highly <i>Z</i>-selective syntheses of oxazolidin-2-ones from propargylic alcohols containing internal alkynes and phenyl isocyanate were achieved by using a combination of silver acetate and <i>N</i>,<i>N</i>-dimethylaminopyridine. The catalytic system was applied to propargylic alcohols containing alkyl-substituted alkyne groups. By considering the results in the presence and absence of an electron-withdrawing group on the aromatics, it was shown that the silver catalyst effectively activates

Herein, direct unreactive C-N borylation of aromatic amines by a photocatalyst was achieved. The C-N borylation of aromatic amines with bis(pinacolato)diboron (B₂pin₂) proceeded using a pyrene catalyst under light irradiation to afford desired borylated products and aminoborane as a byproduct. The yield of the borylated product improved under a CO₂ atmosphere which probably reduced the inhibitory effect of aminoborane. Mechanistic studies suggested that the C-N b

We report carbamoylarylation of alkenes using N-aryl oxamic acid derivatives under visible-light irradiation. Reactions of alkenes with carbamoyl radicals generated using N-aryl oxamic acid derivatives to afford Giese-type products or 3,4-dihydroquinolin-2(1H)-ones via ortho-radical addition to an aryl amide moiety have been previously reported. However, this study reveals that the introduction of a removable bulky group onto the nitrogen atom of N-aryl oxamic acids facilitates the radical addit

Abstract Pyrene is one of the most attractive polycyclic aromatic hydrocarbons (PAHs) in photochemistry. Based on their redox properties, pyrenes have potential as photosensitizers. In this review, we summarize recent developments in pyrene-catalyzed photoinduced organic reactions occurring via energy transfer or single-electron transfer based on the excited state of the pyrene. 1 Introduction 2 Photolysis Involving N–O Bond Cleavage or Decarboxylation 3 (Cyclo)addition Reactions with Styrenes 4

We developed the visible-light-induced hydrodesulfurization of alkyl aryl thioethers via the reductive cleavage of the C(aryl)-S bond using 1-hydroxypyrene as a Brønsted acid-reductant bifunctional photocatalyst. The hydrodesulfurization reaction proceeded under simple reaction conditions (1-hydroxypyrene and Et₃N in THF under purple LED illumination); this reaction did not require chemicals commonly used for hydrodesulfurization, such as hydrosilanes, transition metal catalysts, and/

Titanium dioxide (TiO2) photocatalysis can be applied to pattern proteins and cells under aqueous solution. In this work, we extended the application of this technique to patterning primary neurons, a type of cell with relatively weak adhesibility. For this purpose, we employed ribosomal protein L2 (RPL2) that has high affinity toward silica and metal oxides, including TiO2, to stably bind a neuronal adhesion protein laminin to the TiO2 surface. We utilized two types of molecular recognition to

We have developed a gold-catalyzed cascade reaction of aryldiynes bearing a hydrosilyl group to afford a variety of unexplored 5H-benzo[b]indeno[2,1-d]silines. The reaction system is applicable to the synthesis of bidirectionally π-extended silacycles from tetra(alkynyl)aryl compounds. Computational studies suggest that 5H-benzo[b]indeno[2,1-d]silines are formed via the insertion of a vinyl carbocation intermediate into the Si-H bond.

This study demonstrates the rhodium-catalyzed divergent synthesis of 5-, 5,6-, and 8-membered silacyclic compounds, such as benzosilole, silolosiline, and disilocine, from (2-hydrosilylaryl)acetylenes. To achieve high product selectivity, intra- and intermolecular reactions are controlled by tuning the mono- and bidentate phosphine ligands on the rhodium catalyst precursor. Deuterium labeling experiments and computational studies reveal that the annulation reaction proceeds via hydride transfer