A highly regio- and stereo-selective hydrostannation reaction of various fluorine-containing internal acetylene derivatives

The hydrostannation reaction of various fluoroalkylated acetylene derivatives with tributyltin hydride was investigated using a variety of catalysts in toluene. Among them, the Et₃B-induced hydrostannation reaction gave the highest regio- and stereo-selectivity. Their selectivity was mostly influenced upon the difference of the substituent X at the aromatic ring of the aryl-substituted internal acetylenes. Thus, the acetylenes having a halogen atom or an electron-donating group as X reacted smoothly with tributyltin hydride, affording the vinylstannane 4Z exclusively, while the acetylenes having an electron-withdrawing group (X=CO₂Et, NO₂) resulted in the preferential formation of 5E. The plausible mechanism of the formation of these products was discussed.     

Synthesis and structural revision of eurypamides isolated from the Palauan sponge Microciona eurypa

Eurypamides A and B, 1 and 2, were successfully synthesized by employing Tl(NO₃)₃ (TTN) oxidation of the corresponding halogenated phenols, 9, 16, and 26. This investigation revealed that the dihydroxyarginine residue of 1 should be revised to possess (2S,3R,4S)-configuration. In addition, the synthesis of 2 provided a pure sample, which was previously characterized in a mixture.     

A sequential highly stereoselective hydroboration and Suzuki-Miyaura cross-coupling reaction of fluoroalkylated internal acetylenes: a practical one-pot synthesis of fluoroalkylated trisubstituted alkenes

The one-pot synthesis of trisubstituted alkenes starting from fluoroalkylated internal alkynes was investigated. Hydroboration of the alkynes proceeded in a highly regio- and stereoselective manner to give the corresponding vinylboranes in excellent yields. Without isolation, treatment of the vinylboranes with various aryl halides under the Suzuki-Miyaura cross-coupling conditions gave the fluoroalkylated trisubstituted alkenes in high yields with complete retention of the olefinic geometry.     

Complete reversal in regioselectivity in the Baeyer-Villiger reaction of an alpha-CF(3)-ketone and theoretical rationale for axial orientation of sterically demanding CF(3) group at the transition state

The regioselectivity of the Baeyer-Villiger reaction of alpha-CF(3)-ketone is completely reversed from that in alpha-F(eq)-ketone. Theoretical study rationalized that the reaction proceeds with the sterically demanding CF(3) group in an axial orientation by strong dipole interaction. The guiding principle that strong dipole interaction can overcome steric repulsion as a determining factor not only in regio- but also in stereocontrol is proposed. [reaction: see text]     

Active control of catalysis and product selectivity by a fuel cell system

A new concept to control catalysis and catalytic reaction through partial oxidation of alkenes with O₂ is described. Oxidation of alkenes was studied by alkene/Pd-anode/H₃PO₄-electrolyte/cathode/O₂ fuel cell (FC). An idea based on electrocatalysis and electrochemical reactions to control reaction rates and product selectivity was proposed and proven through the oxidation of propylene, Wacker and π-allyl oxidation. The oxidation rate and the product selectivity to the Wacker and the π-allyl oxidations could be controlled by changing electrode potentials. We could active control oxidation states of Pd on the anode, Pd(II) or Pd(0), during the oxidation from outer circuit. The oxidation states of Pd on the anode decided the product selectivity.     

Adsorption of dioctyldimethylammonium chloride at water/hexane interface

The adsorption behavior of dioctyldimethylammonium chloride at water/ hexane interface has been studied by measuring the interfacial tension as a function of temperature and pressure at various bulk concentrations. By applying the thermodynamics of adsorption at interfaces to the experimental results, the thermodynamic quantity changes associated with adsorption and the interfacial density of dioctyldimethylammonium chloride have been evaluated.The interfacial tension vs temperature and concentration curves have shown the breaks and it has been concluded that the first order phase transition takes place between a gaseous and an expanded state. The entropy and volume changes associated with adsorption have shown the remarkable dependence on temperature and pressure and have been found to decrease with increasing the molality. Also the energy change associated with adsorption has been evaluated and it has been concluded that the adsorption of dioctyldimethylammonium chloride at water/hexane interface is enhanced by negative values of the partial molar energy change. Further, all the thermodynamic quantities have been characterized by the discontinuous change attributable to the phase transition.     

A first regioselective synthesis of 3-fluoroalkylated benzofurans via palladium-catalyzed annulation of fluorine-containing internal alkynes with variously substituted 2-iodophenol

The palladium-catalyzed annulation reaction of a variety of fluorine-containing internal alkynes with 2-iodophenol derivatives was investigated. The use of P(t-Bu)₃ as a ligand on palladium was found to be crucial in this annulation reaction, resulting in the exclusive formation of 3-fluoroalkylated benzofurans in high yields. ¹⁹F NMR analysis of the reaction mixture revealed that the addition of phenol to the fluoroalkylated alkynes was followed by intramolecular Heck reaction, giving to the corresponding 3-fluoroalkylated benzofurans.     

Analysis of thiamine in dried yeast by high-performance liquid chromatography and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry

Summary High-performance liquid chromatography (HPLC) and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/APCI-MS) have been applied to the analysis of thiamine in dried yeast. Thiamine was extracted from dried yeast with isobutanol containing sodium 1-octanesulfonate as an ion-pairing agent and determined by HPLC on a reversed phase ODS column with UV detection at 254 nm. Response was linear in the range 25–300 μg/g of thiamine in dried yeast with a coefficient of variation in the reproducibility of 8.0%. Thiamine was recovered in good yield (109.2%, n=5). Identification of the thiamine peak was obtained by the mass spectrum using the HPLC/APCI-MS system. The utility of the selected ion monitoring technique using the HPLC/APCI-MS was also investigated. The results obtained by this method are in good agreement with those obtained by the thiochrome method [1].     

Lithium intercalation in layer structured compound β-ZrNCl

A layer structured crystal -ZrNCl forms a lithium intercalation compound Li_xZrNCl. The upper limit for x determined on the compound prepared by the n-butyl lithium technique is 0.29. In the electrochemical process, a pressed -ZrNCl cathode is further reduced up to x=11.25 at potentials as low as 0.80.6 V relative to Li/Li⁺. The lithium intercalate swells in various polar solvents, increasing the basal spacing. However, in contrast to the salt-like intercalates of transition metal chalcogenides and FeOCl, the lithium intercalated -ZrNCl does not form hydration phases, but reacts with water, evolving hydrogen. These results can be interpreted in terms of the formation of an alloy-like intercalate like the alkali intercalates of graphite. On intercalation, -ZrNCl is changed from pale yellow-green to black in color, and the electrical conductivity increases by a factor of 10⁶.     

‘Fluorous nanoflow’ system for the Mukaiyama aldol reaction catalyzed by the lowest concentration of the lanthanide complex with bis(perfluorooctanesulfonyl)amide ponytail

‘Fluorous nanoflow’ system is extremely effective for the lanthanide bis(perfluorooctanesulfonyl)amide-catalyzed Mukaiyama aldol reaction with dramatic increase in the reaction rate by the continuously controlled nano feeder. Thus, the acceleration of the aldol reaction was achieved even in the lowest concentration (<0.0001 M) of the lanthanide fluorous catalyst and, hence, the reaction completed within seconds as a bi-phase contact time in the micro cell.