Catalytic asymmetric cyano-ethoxycarbonylation reaction of aldehydes using a YLi3 tris(binaphthoxide) (YLB) complex: mechanism and roles of achiral additives

Full details of a catalytic asymmetric cyano-ethoxycarbonylation reaction promoted by a heterobimetallic YLi3 tris(binaphthoxide) complex (YLB 1), especially mechanistic studies, are described. In the cyanation reaction of aldehydes with ethyl cyanoformate, three achiral additives, H2O, tris(2,6-dimethoxyphenyl)phosphine oxide (3a), and BuLi, were required to achieve high reactivity and enantioselectivity (up to >99% yield and up to 98% ee). The roles of achiral additives and the reaction pathway were investigated in detail. In situ IR analysis revealed that the initiation step to generate LiCN from H2O, BuLi, and ethyl cyanoformate is rather slow. On the basis of mechanistic studies of the initiation step to generate an active nucleophilic species, reaction conditions were optimized by using a catalytic amount of acetone cyanohydrin as an initiator. Under the optimized conditions, the induction period decreased and the reaction completed within 9 min using 5 mol % YLB at -78 degrees C. Catalyst loading was successfully reduced to 1 mol %. Kinetic experiments and evaluation of the substituent effects of phosphine oxide revealed that phosphine oxide had beneficial effects on both the reaction rate and the enantioselectivity. The putative active species as well as the catalytic cycle of the reaction are also discussed.     

Bismuth‐ and Hafnium‐Catalyzed Hydroamination of Vinyl Arenes with Sulfonamides,Carbamates, and Carboxamides

Catalytic intermolecular hydroamination of vinyl arenes is described. Our initial investigation revealed that a Bi(OTf)₃/[Cu(CH₃CN)₄]PF₆ system previously developed for catalytic intermolecular hydroamination of 1,3‐dienes was suitable for hydroamination of a styrene with sulfonamides, but the substrate generality of this system was unsatisfactory. Several metals were screened to expand the substrate scope, and a new Hf(OTf)₄/[Cu(CH₃CN)₄]PF₆ system was determined to be highly suitable. The combination of Hf(OTf)₄ and [Cu(CH₃CN)₄]PF₆ efficiently promoted the hydroamination of various vinyl arenes, including less‐reactive vinyl arenes with electron‐withdrawing groups. This strategy was applied to sulfonamides, carbamates, and carboxamides, and products were obtained in up to 99 % yield with 0.3–10 mol % catalyst loading.     

A short and efficient asymmetric synthesis of komaroviquinone

An asymmetric total synthesis of komaroviquinone (1), which is a natural product isolated from Dracocephalum komarovi and shows novel potent trypanocidal activity, was achieved in five steps from the known starting materials. The synthetic route is shorter and more efficient than the reported methods and also useful for the scale-up synthesis.     

Ion heating by lower hybrid waves

An ion heating by excited lower hybrid waves has been observed in a coaxial type double plasma device. The lower hybrid resonance heating is examined on the two components of the kinetic energy perpendicular and parallel to the magnetic field.     

Adsorption characteristics of organic dyes in aqueous solutions on mixed-oxide gels

Summary Five alumina-containing gels were investigated on the adsorption characteristics for four types of organic dyes (acidic, basic, reactive, and direct dyes). Alumina-magnesias exhibited the properties as strong solid bases and adsorbed effectively three dyes except for the acidic dye. While, alumina-silicas, strong solid acids, showed the high ability only for the acidic dye.

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Adsorptionscharakteristica organischer Farbstoffe in wäßrigen Lösungen auf gemischten OxidgelenII. Aluminiumoxid-haltige gemischte Oxidgele

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Part I: see [5]     

A new nondestructive approach to chemical analysis of potsherds using an X‐ray fluorescence microscope: Case study about the past pottery manufacture in the Yaeyama Islands

In archeology, pottery represents an important class of artifacts giving information on the past human activity, the ecology, and ancient cultural groups. Some chemical analytic methods, including X‐ray fluorescent analysis, were adopted for the archeological study of pottery. However, these techniques also involve problems, including the destructive analysis of materials, and cannot analyze the original clay condition of pottery. To address this, we carried out nondestructive chemical analysis of 13 potsherds excavated from the Yaeyama Islands in the southern Japan archipelagos using X‐ray fluorescence microscopy. Two analytic methods were used, elemental mapping and multipoint spectral measurement, making it possible to obtain a visualized elemental distribution on potsherd surface and a detailed multipoint elemental composition of the same sample for the multivariate statistical analysis. In this study, the visualized images suggested that calcium particles were mixed to temper the materials, and their size and quantity differed between potsherds, whereas the uniformity of clay substrate, including the quantities of iron and silicon on multipoint measurement, was a characteristic of each potsherd. Therefore, principal component analysis and nonmetric multidimensional scaling analysis of the potsherds suggest that the differences between the Yaeyama Islands in terms of pottery manufacturing technology are due to chronological factors in this case. Our method represents an effective new approach to the pottery study for technological change.     

Tunable high-energy ion source via oblique laser pulse incident on a double-layer target

The laser-driven acceleration of high quality proton beams from a double-layer target, comprised of a high-Z ion layer and a thin disk of hydrogen, is investigated with three-dimensional particle-in-cell simulations for an obliquely incident laser pulse. The proton beam energy reaches its maximum at a certain incidence angle, where it can be much greater than the energy at normal incidence. The proton beam propagates at some angle with respect to the target surface normal and with some tilt around the target surface, as determined by the proton energy and the incidence angle.     

Study on retention behavior of cyclic siloxanes by high resolution pyrolysis-gas chromatography with a fused silica capillary column

The general gas chromatographic retention behavior of cyclic methylsiloxanes partially substituted with phenyl or 2-cyanoethyl groups has been systematically studied, with pyrolysis-gas chromatography being utilized to form the cyclic siloxanes from the corresponding polysiloxanes at a temperature of 600°C. Kovats retention indices (KI) were determined for the cyclic siloxanes by use of the retention data of the pyrolyzates from polyethylene as standards. The effect of phenyl and 2-cyanoethyl substituents in the cyclic siloxanes on retention behavior has also been considered.