Mechanism of BPh3-Catalyzed N-Methylation of Amines with CO2 and Phenylsilane: Cooperative Activation of Hydrosilane

BPh₃ catalyzes the N-methylation of secondary amines and the C-methylenation (methylene-bridge formation between aromatic rings) of N,N-dimethylanilines or 1-methylindoles in the presence of CO₂ and PhSiH₃; these reactions proceed at 30–40 °C under solvent-free conditions. In contrast, B(C₆F₅)₃ shows little or no activity. ¹¹B NMR spectra suggested the generation of [HBPh₃]⁻. The detailed mechanism of the BPh₃-catalyzed N-methylation of N-methylaniline ( 1 ) with CO₂ and PhSiH₃ was studied by using DFT calculations. BPh₃ promotes the conversion of two substrates (N-methylaniline and CO₂) into a zwitterionic carbamate to give three-component species [Ph(Me)(H)N⁺CO₂⁻⋅⋅⋅BPh₃]. The carbamate and BPh₃ act as the nucleophile and Lewis acid, respectively, for the activation of PhSiH₃ to generate [HBPh₃]⁻, which is used to produce key CO₂-derived species, such as silyl formate and bis(silyl)acetal, essential for the N-methylation of 1 . DFT calculations also suggested other mechanisms involving water for the generation of [HBPh₃]⁻ species.     

Depth estimation of protoporphyrin IX objects in turbid media considering the fluorescence intensity ratio between two wavelengths of light for application in invasion diagnosis of gastric cancer

Optical Review - This paper demonstrates a method to estimate the depth of a fluorescence object in turbid media using dual-wavelength excited photodynamic diagnosis, to aid in the invasion depth...     

Manuals in orthogonal categories

The notion of a manual, introduced and investigated in detail by Foulis, Randall, and their followers, has turned out to be further reaching than its originators had envisaged. Its omnipresence is comparable with the notion of a sheaf, whose significance is well recognized by every pure and applied mathematician. The principal concern of this paper is to give an appropriate vehicle, as general as possible, by which the theory of manuals can be developed. The vehicle is called an orthogonal category, which is akin to the notion of a category with coproducts. Orthogonal categories provide also a new perspective on the notion of a sheaf over a complete Boolean algebra, deepening our comprehension of Boolean mathematics and paving the way to quantum mathematics.     

Characterization of metal binding properties of rhamnogalacturonan II from plant cell walls by size-exclusion HPLC/ICP-MS.

The binding properties of metal ions to a pectic polysaccharide, rhamnogalacturonan II (RG-II), from plant cell walls were analyzed by size-exclusion HPLC/ICP-MS. The dimeric RG-II borate complex (dRG-II-B) from sugar beet and red wine contained 0.8 - 1.1 mol/mol of B, 0.8 - 1.1 mol/mol of Ca, 0.1 - 0.3 mol/mol of Sr, and 0.03 - 0.07 mol/mol of Ba. The treatment of dRG-II-B with Sr2+, Ba2+, Pb2+ or La3+ exchanged the originally present Ca, Sr and Ba. In contrast, monomeric RG-II (mRG-II), which contained approximately 0.1 mol/mol of Ca, formed complexes with La3+, Eu3+, and Lu3+ added to the solution, but did not do so with Ca2+, Sr2+, Ba2+ and Pb2+. The HPLC/ICP-MS and HPLC/RI (refractive index detector) analysis of the partially hydrolyzed mRG-II that was treated with La3+ indicated that the side chains and backbone of mRG-II together form a lanthanoid binding site.     

Some remarks on projectively flat complex Finsler metrics

In this paper, we hall discuss the projective flatness of complex Finsler metrics by investigating the geometry of projective bundles associated with a holomorphic vector bundle.     

Interpretation of initial stage of 3C-SiC growth on Si(1 0 0) using dimethylsilane

The initial stage of cubic silicon carbide (3C-SiC) growth on a Si(0 0 1) surface using dimethylsilane (DMS) as a source gas was observed using scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED). It was found that the dimer vacancies initially existing on the Si(0 0 1)-(2 × 1) surface were repaired by the Si atoms in DMS molecules, during the formation of the c(4 × 4) surface. From the STM measurement, nucleation of SiC was found to start when the Si surface was covered with the c(4 × 4) structure but before the appearance of SiC spots in the RHEED pattern. The growth mechanism of SiC islands was also discussed based on the results of RHEED, STM and temperature-programmed desorption (TPD).     

Stage-specific and age-dependent profiles of zinc, copper, manganese, and selenium in rat seminiferous tubules

Stage-specific and age-dependent profiles of zinc, copper, manganese, and selenium in testis were examined in Wistar rats by both inductively coupled argon plasma-mass spectrometry (ICP-MS) with a microdissection technique and in situ elemental imaging of micro-PIXE analysis. The young adult animals (10 weeks old) contained higher levels of zinc and manganese in the seminiferous tubules at stages VII-VIII than stages XI through VI and IX-X and the levels were higher than those of the immature and old animals. Copper and selenium levels at stages VII-VIII of the young adult animals were also higher than those of the immature and old animals. In stages VII and VIII, zinc was higher in the central area of the seminiferous epithelium, where spermatozoa were localized, demonstrating a cell-specific property. This revised version was published online in August 2006 with corrections to the Cover Date.