The birch reduction of heterocyclic compounds. 11. Birch reduction and reductive alkylation of furamides

The Birch reduction-alkylation of some N,N-dialkylfuramides and its application to the useful intermediates for the natural product synthesis are described.     

In-situ observations of dissolution process of GaSb into InSb melt by X-ray penetration method

Dissolution process of GaSb into InSb melt was observed by an X-ray penetration method. The intensity of X-rays penetrated through the rectangular shaped GaSb (seed)/InSb/GaSb (feed) sandwich sample was recorded by the CdTe line sensor detector. The penetrated X-ray intensities and images of the sample were obtained as a function of time and temperature. The gallium (Ga) composition profile of the sample was calculated as a function of time by making the calibration line with the penetrated X-ray intensities of GaSb and InSb standard samples. The calculated Ga composition profile of the grown sample agreed well with the data measured by energy dispersive X-ray spectroscopy analysis. The result suggested that lower GaSb seed dissolved faster than upper GaSb feed despite of the low temperature at the lower GaSb seed. It clearly indicates that the solutal transport induced by gravity strongly affects the dissolution process.     

Unsteady and chaotic characteristics of natural convection field in vertical slots at large Prandtl number

In this study we examined the unsteady and chaotic characteristics of the natural convection field in vertical slots at large Prandtl number. In the computation, temperature dependence of viscosity was partially taken into consideration. As a result we discovered that the spatial region where a significant temperature fluctuation is detected corresponds to the spatial region where the secondary cells exist. The largest Lyapunov exponents calculated from the temperature on the center line have a local maximum at the lower region of the enclosure when the viscosity change was considered. These characteristics agree well with the experimental ones that have been observed by authors (Ishida, Kure and Kimoto 2001).     

Synthesis of hyperolactones A and C

Hyperolactones A ( 1 ) and C ( 3 ) have been synthesized starting from (S)‐malic acid by a straightforward route. The unique spirolactone skeleton was efficiently constructed by one‐pot reaction as a key step. The absolute stereochemistry of hyperolactones was unambiguously established by this synthesis.     

Photochemical tuning of the helical structure of cholesteric liquid crystals by photoisomerization of chiral azobenzenes, and their structural effects

Several chiral azobenzene compounds having different chiral substituents were synthesized. A cholesteric phase was induced by mixing each chiral azobenzene compound with a host non-chiral nematic liquid crystal (E44). The helical twisting power (HTP) as well as the change in HTP by trans-cis photoisomerization of the chiral azobenzene compound was dependent on the structure of the chiral substituents. A compensated nematic phase was induced by combination of E44, a chiral azobenzene compound and a non-photochromic chiral compound. Reversible switching between the compensated nematic phase and cholesteric phase was brought about by trans-cis photoisomerization of the chiral azobenzene compound in the liquid crystalline systems. An azobenzene compound substituted with a menthyl group showed the highest efficiency as the trigger for the switching; this efficiency was related to the compactness of the chiral group substituted within the azobenzene core moiety.     

Rotamers of some radical-ions as evidenced by optical and ESR spectroscopy

Conformational isomerizations of radical-ions are studied both experimentally and theoretically. The representative systems of stilbenes, polyenes, and non-planar alicyclic compounds will be reviewed first. Then, the result of the study on the radical-cations of 1,4-dithiacyclohexane and ethane-1,4-dithiol will be presented. It is found that the former cation suffers a change from a chair form to a boat form and the latter from an anti- or a gauche-form to a cis form even in a rigid matrix. The conformational changes are manifested by drastic changes in the electronic absorption and ESR spectra. The strong “through-space” interaction between the lone pair orbitals of the sulfur atoms is responsible for the conformational changes. Ab initio MO calculations lend support to the analysis of the experimental results.     

Thickness and Surface Profile Measurement by a Sinusoidal Wavelength-Scanning Interferometer

We propose a sinusoidal wavelength-scanning interferometer for measuring thickness and surface profile of a thin film. The interference signal contains phase modulation amplitude Z and phase $aL which are related to the positions and profiles of the reflecting surfaces, respectively. By reducing the difference between the detected signal and the estimated signal using the multidimensional nonlinear least-squares algorithm, we estimate values of Z and $aL. Experimental results show that the front and rear surfaces of a silica glass plate of 20 $mUm-thickness could be measured with an error less than 10 nm.