Synthesis of N-cyano monoaza crown ethers

N-Cyano monoaza crown ethers were prepared by the reaction of cyanamide with oligoethylene glycol dichlorides or ditosylates in the NaH/DMSO reaction system and led to the derivatives.     

Air-assisted addition of grignard reagents to olefins. A simple protocol for a three-component coupling process yielding alcohols

Silylmethyl, tertiary-alkyl, alkenyl, and aryl Grignard reagents underwent intermolecular addition to olefins, such as styrenes, conjugated dienes, and enynes under an air atmosphere to give homologated alcohols. For example, (trimethylsilyl)methylmagnesium chloride and alpha-methylstyrene in ether at room temperature under dry air directly furnished 2-phenyl-4-(trimethylsilyl)-2-butanol in good yield. As the Grignard addition to olefins under argon with rigorous exclusion of O2 did not proceed at all, the above reaction should involve a radical mechanism: an alkyl radical generated by the aerial oxidation of the Grignard reagent adds to olefin, which is followed by oxygenation. Representative examples of this transformation, where products were obtained in good to excellent diastereo- or regioselectivity, are also disclosed.     

Successive Linearization Methods for Nonlinear Semidefinite Programs

We present a successive linearization method with a trust region-type globalization for the solution of nonlinear semidefinite programs. At each iteration, the method solves a quadratic semidefinite program, which can be converted to a linear semidefinite program with a second order cone constraint. A subproblem of this kind can be solved quite efficiently by using some recent software for semidefinite and second-order cone programs. The method is shown to be globally convergent under certain assumptions. Numerical results on some nonlinear semidefinite programs including optimization problems with bilinear matrix inequalities are reported to illustrate the behaviour of the proposed method.The research of the fourth author was supported in part by a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science. The research of the second author was supported by the DFG (Deutsche Forschungsgemeinschaft).     

Raman scattering in low wavenumber region as a new probe to structural properties of microcrystalline silicon

The structural properties of microcrystalline silicon (μc-Si) are studied by Raman scattering. It is found that the intensity of each Raman band closely correlates with the absorption coefficient in the interband region and that the Raman band at ca. 150 cm^?1 is a sensitive probe to randomness of Si-Si bonding structure in μc-Si.     

Selective determination of pentoses,hexoses and 6-deoxyhexoses by dual-wavelength spectrophotometry with the cysteine—phenol—sulfuric acid system

A convenient method is described for the selective determination of pentoses, hexoses and 6-deoxyhexoses by dual-wavelength spectrophotometry with the l-cysteine—phenol—sulfuric acid system. Excellent linearity was observed for 25–250 nmol of pentoses, and for 25–500 nmol of hexoses and 6-deoxyhexoses. These aldoses in those sample ranges could be determined selectively with high accuracy and precision by the k -factor mode. The appropriate, wavelength of λ₂ was 462, 499 and 398 nm for pentoses, hexoses and 6-deoxyhexoses, respectively, whereas that of λ₁ was commonly 424 nm.     

Cation-controlled assembly of Na+-linked lacunary alpha-Keggin tungstosilicates

Two novel salts of lacunary tungstosilicates with guanidinium and alkali metal cations, (CH6N3)7Na[SiW11O39].(CH3)2CO.8H2O (1) and (CH6N3)K6Na[SiW11O39].11.5H2O (2), have been synthesized and their crystal structures have been determined by synchrotron X-ray diffraction. In both crystals, the Na+ cations link the lacunary Keggin-type tungstosilicate anions into linear structures. The neighboring [SiW11O39]8- anions are related by two-fold screw and translational operations in compounds 1 and 2, respectively. Second harmonic generation was observed for compound 1.     

Spatial arrangement of metal nanoparticles supported by porous polymer substrates studied by transmission electron microtomography

Fine metal particles (nanoparticles) stabilized on porous (polymeric) substrates can be considered as a model system of a high-performance catalyst. In the present study, the substrate was made using the periodic microphase-separated structure of a block copolymer as the template, and the Pd nanoparticles were formed inside the porous material by reduction of the Pd2+ ions with 1-propanol as the reductant. The three-dimensional morphology of such a polymer-Pd hybrid material was studied by transmission electron microtomography. The characteristic structural parameters of the hybrid, e.g., the penetration of the Pd nanoparticles into the polymer substrate, number density of the Pd nanoparticles, and size distribution of the Pd nanoparticles, were measured for the first time.     

Possibility of a non-amino acid pathway in the biosynthesis of marine-derived oxazoles

A novel avenue for oxazoles via Beckmann rearrangement of alpha-formyl ketoxime dimethyl acetals is described that indicates the possibility of a non-amino acid biosynthetic pathway in marine natural products.