Addition of ArSSAr to carbon-carbon multiple bonds using electrochemistry

ArS(ArSSAr)⁺ (arylbis(arylthio)sulfonium ions), which were generated and accumulated by the electrochemical oxidation of diaryl disulfides (ArSSAr) in CH₂Cl₂ at −78 °C, reacted with alkenes to give the corresponding diarylthio-substituted compounds in a stereospecific manner in good yields, when the reaction was quenched with a soft nucleophile, such as allylsilanes, ketene silyl acetals, and triethylamine. A mechanism involving the initial formation of an episulfonium ion followed by ring-opening by the attack of ArSSAr has been suggested. The reactions of ArS(ArSSAr)⁺ with alkynes also took place to give 1,2-diorganothio-substitued alkenes stereoselectively under similar conditions.     

Effect of industrial water components on thermal stability of nitrocellulose

In order to prevent the spontaneous ignition of nitrocellulose (NC), NC is stabilized by washing with industrial water in its synthesis process. However, there is a possibility that the components in industrial water contribute to the thermal stability of NC. In this way, the purpose of this study is to clarify the effect of industrial water components on the thermal stability of NC. In experiments, a heat flux calorimeter was used to observe the thermal behavior of NC with the residue of vaporized industrial water. The induction period of heat release of NC with 2-mass% residues was approximately 2–5 h shorter than that of NC alone whose induction period was observed at 7 h. Those results indicate that the residue destabilized NC. On the other hand, when the additive amount of the residue was increased, the induction period gradually increased as well. Based upon these results, we assume that inorganic salts contributing to stabilization and destabilization competitively coexist in the industrial water components. The same thermal analysis was performed on NC with CaCO₃, CaSO₄, CaCl, ZnSO₄, NaCl, and CuCl. Those salts are predicted to exist in the industrial water. In the results, the induction period of NC with 2-mass% CaCO₃ was approximately 15-h longer than that of NC alone, while the induction period with the inorganic salts CaSO₄, CaCl, ZnSO₄, NaCl, and CuCl was 4–5-h shorter. Therefore, when the industrial water components accumulate in NC, the destabilization by inorganic salts such as CaSO₄, CaCl, ZnSO₄, NaCl, and CuCl and the stabilization by compounds such as CaCO₃ are thought to countervail against each other.     

Rhodium(III)-catalyzed synthesis of isoquinolines from aryl ketone O-acyloxime derivatives and internal alkynes

A synthetic method of isoquinolines from aryl ketone O-acyloxime derivatives and internal alkynes has been developed using [Cp*RhCl(2)](2)-NaOAc as the potential catalyst system. The present transformation is carried out by a redox-neutral sequence of C-H vinylation via ortho-rhodation and C-N bond formation of the putative vinyl rhodium intermediate on the oxime nitrogen, where the N-O bond of oxime derivatives could work as an internal oxidant to maintain the catalytic cycle.     

Electrochemically stable fluorohydrogenate ionic liquids based on quaternary phosphonium cations

Fluorohydrogenate ionic liquids of quaternary phosphonium cations, tri-n-butylmethylphosphonium (P₄₄₄₁) fluorohydrogenate, tetra-n-butylphosphonium (P₄₄₄₄) fluorohydrogenate, and tri-n-butyl-n-octylphosphonium (P₄₄₄₈) fluorohydrogenate, have been synthesized by the metatheses of anhydrous hydrogen fluoride and the corresponding phosphonium chloride precursors. All the obtained salts have melting points below room-temperature with a vacuum-stable composition of P_444m(FH)_2.3F (m = 1, 4, and 8) and were characterized by density, conductivity, and viscosity measurements. Linear sweep voltammetry with a glassy carbon working electrode shows that the P_444m(FH)_2.3Fs have wide electrochemical windows exceeding 5.2 V. In particular, P₄₄₄₁(FH)_2.3F has an electrochemical window of 6.0 V, which is the widest among fluorohydrogenate ionic liquids reported to date. The thermal stability of these ionic liquids is also improved compared to the salts of N-heterocyclic ammonium cations.     

Trichlorosilyl triflate for enantioselective direct-type aldol reaction with chiral phosphine oxide

Trichlorosilyl triflate, in the presence of a chiral Lewis base catalyst, provides an effective method for the enantioselective direct-type aldol reaction of aldehydes and ketones. A chiral Lewis base induces both the production and activation of trichlorosilyl enol ether, yielding an aldol product in good yield and with high diastereo- and enantioselectivities.     

Enantioselective reductive aldol reaction using tertiary amine as hydride donor

An efficient method was developed for the enantioselective reductive aldol reaction of α,β-unsaturated ketones with aldehydes in the presence of a Lewis base catalyst; conjugate reduction using a tertiary amine and trichlorosilyl triflate, followed by an aldol reaction with BINAP dioxide (BINAPO) as an organocatalyst, gave the corresponding product in high yield with high stereoselectivity.     

Transfer efficiency in ballistic electron emission microscopy taking diffraction of emitted hot electrons into account

We have analyzed the transfer efficiency of ballistic electron emission microscopy (BEEM), taking the finite spot size of the emitted electron beam from scanning probes into account. Three-dimensional diffraction from an aperture at a surface-metal/air interface is introduced to model an effect caused by the finiteness of spot size. As a general trend, the diffraction decreases BEEM transfer efficiency. The diffraction effect increases as the spot size decreases and the air-gap distance increases. In a Au/GaAs sample, BEEM transfer efficiency markedly deteriorates down to 6% of the value derived from a conventional planar tunneling theory when a spot size of 0.2 nm, an air-gap distance of 0.6 nm, and an electron energy of 0.2 eV, measured from the bottom of the GaAs conduction band, are assumed. BEEM transfer efficiency is markedly dependent on the spot size of the emitted hot electron. This result indicates that the BEEM current depends on the spatial resolution of the scanning probe, that is, the condition of the tip apex.     

Theoretical Analysis of Super-Resolution Optical Disk Mastering Using a Photoreactive Dye Mask Layer

The super-resolution mastering of read-only optical disks using a photoreactive bleachable dye mask layer was theoretically analyzed. Equations have been derived which describe the photoreactions of the resist layer and mask layer. A numerical simulation based on these equations showed that the transmittance of the mask directly affects the quality of the formed pit shape. A high-quality pit shape is obtained by using a low transmittance mask.