Sodium methoxide: a simple but highly efficient catalyst for the direct amidation of esters

A simple NaOMe catalyst provides superior accessibility to a wide variety of functionalized amides including peptides through direct amination of esters in an atom-economical and environmentally benign way.     

Application of photoactive yellow protein as a photoresponsive module for controlling hemolytic activity of staphylococcal α-hemolysin

A chimeric protein (N-PYP-Hla), consisting of staphylococcal pore-forming toxin α-hemolysin (Hla) and photoactive yellow protein (PYP), exhibited photoresponsive hemolytic activities, where visible light irradiation gave rise to retardation of hemolysis at 25 °C.     

Photocatalytic oxidation of 2-propanol under visible light irradiation on TiO<Subscript>2</Subscript> thin films prepared by an RF magnetron sputtering deposition method

Visible light-responsive TiO₂ (Vis-TiO₂) thin films able to absorb UV and visible light in wavelength regions of 250–600 nm were successfully developed by applying a radio-frequency magnetron sputtering deposition method. These Vis-TiO₂ thin films exhibited high activity for the photocatalytic oxidation of 2-propanol diluted in water even under visible light irradiation (λ ≥ 450 nm). The photocatalytic activity of Vis-TiO₂ thin films was dramatically enhanced by the deposition of Pt particles on the surface. Secondary ion mass spectrometry measurements revealed that Pt particles are distributed from the top surface to the deep bulk of Vis-TiO₂ thin films with a columnar structure. The unique columnar structure of Vis-TiO₂ thin films plays an important role in the high photocatalytic performance.     

Catalysis of Ruthenium-Metal Oxides Mechanically Mixed with Sulfated Zirconia for Reaction of Butane to Isobutane

A highly active catalyst for the skeletal isomerization of butane to isobutane was obtained by mechanically mixing SO₄/ZrO₂ and Ru/SnO₂; Ru/SO₂ was prepared by impregnating tin hydroxide with a solution of RuCl₃ followed by calcining at 450°C (0.5 wt.% Ru). The catalyst was much more active than Ru-SO₄/ZrO₂ prepared by co-impregnation of zirconia with the Ru and sulfate materials the temperature difference to show the same conversion between both catalysts being 57°C. The effect of mixing of Ru was observed with other metal oxides as supports, Fe₂O₃, Al₂O₃, ZrO₂, TiO₂, and SiO₂; the calcination temperature of the Ru-impregnated hydroxides was 250, 300, and 400°C for the latter three, respectively.     

Trivalent Rare-Earth Metal Amide Complexes as Catalysts for the Hydrosilylation of Benzophenone Derivatives with HN(SiHMe2)2 by Amine-Exchange Reaction

The rare-earth metal complexes Ln( L¹ )[N(SiHMe₂)₂](thf) (Ln=La, Ce, Y; L¹ =N,N′′-bis(pentafluorophenyl)diethylenetriamine dianion) were synthesized by treating Ln[N(SiHMe₂)₂]₃(thf)₂ with L¹ H₂. The lanthanum and cerium derivatives are active catalysts for the hydrosilylation of benzophenone derivatives with HN(SiHMe₂)₂. An amine-exchange reaction was revealed as a key step of the catalytic cycle, in which Ln−Si−H β-agostic interactions are proposed to promote insertion of the carbonyl moiety into the Si−H bond.     

Studies toward the total synthesis of gambieric acids, potent antifungal polycyclic ethers: convergent synthesis of the CDEFG-ring system

[reaction: see text] A convergent synthetic route to the CDEFG-ring system of gambieric acids, potent antifungal polycyclic ether marine natural products, has been developed. The present synthesis features convergent union of the CD- and G-rings through esterification, formation of the E-ring as a lactone form, stereoselective allylation to set the C26 stereocenter, and ring-closing metathesis reaction to construct the nine-membered F-ring.     

A New Protocol to Generate Catalytically Active Species of Group 4–6 Metals by Organosilicon-Based Salt-Free Reductants

Herein, we provide a new protocol to reduce various transition-metal complexes by using organosilicon compounds in a salt-free fashion with the great advantage of generating pure low-valent metal species and metallic(0) nanoparticles, in sharp contrast to reductant-derived salt contaminants obtained by reduction with metal reductants. The organosilicon derivatives 1,4-bis(trimethylsilyl)-2,5-cyclohexadiene ( 1 a ), 1-methyl-3,6-bis(trimethylsilyl)-1,4-cyclohexadiene ( 1 b ), 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene ( 2 a ), 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene ( 2 b ), 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene ( 2 c ), and 1,1′-bis(trimethylsilyl)-1H,1′H-4,4′-bipyridinylidene ( 3 ) all served as versatile reductants for early transition-metal complexes and produced only easy-to-remove organic compounds, such as trimethylsilylated compounds and the corresponding aromatics, for example, benzene, toluene, pyrazine, and 4,4′-bipyridyl, as the byproducts. The high solubility of the reductants in organic solvents enabled us to monitor the catalytic reactions directly and to detect any catalytically active species so that we could elucidate the reaction mechanism.     

Direct conversion of esters, lactones, and carboxylic acids to oxazolines catalyzed by a tetranuclear zinc cluster

The tetranuclear zinc cluster Zn4(OCOCF3)6O catalyzes the direct conversion of esters, lactones, and carboxylic acids to oxazolines with remarkable chemoselectivity.     

Homological Mirror Symmetry for Toric del Pezzo Surfaces

We prove the homological mirror conjecture for toric del Pezzo surfaces. In this case, the mirror object is a regular function on an algebraic torus We show that the derived Fukaya category of this mirror coincides with the derived category of coherent sheaves on the original manifold. Supported by JSPS Fellowships for Young Scientists No.15-5561.     

Effect of adhesion force between crack planes on subharmonic and DC responses in nonlinear ultrasound

Subharmonic and DC responses in nonlinear ultrasound have been expected as a possible means of detecting closed cracks. Recently, it has been reported that subharmonics in a closed crack markedly increases above a certain input wave amplitude. Such a phenomenon is called "threshold behavior". However, the mechanism of threshold behavior has yet to be elucidated. To clarify this, we introduced adhesion force as a short-range force into the previous analytical model, which expresses the nonlinear contact vibrations of crack planes with intense ultrasound and provides a DC displacement as an approximation of the subharmonic response. Consequently, upward convex curves of displacement against input wave amplitude above the threshold were reproduced for the first time. The validity of the derived analytical solution is discussed by comparison with experimentally observed subharmonics.