Effect of alkoxy terminal chain length on mesomorphism of 1,6-disubstituted pyrene-based hexacatenar liquid crystals: columnar phase control

Synthesis and mesophase-transition behaviors of six 1,6-disubstituted pyrene-based hexacatenar liquid crystals 1_n (n=8–18) are reported here. They were synthesized by the Sonogashira coupling between 1,6-diethynylpyrene and 2-bromothiophene bearing a trialkoxybenzoyl group. The phase-transition behavior was studied by differential scanning calorimetry and polarized optical microscopy; a few mesophase progressions, I–Col/I–X–Col and Col–Sm, were observed, where X was an optically isotropic but unidentified phase. The structures of Col_r, Col_h, and Sm phases were analyzed by the X-ray crystallography, and the effect of the terminal alkoxy chain length on the mesomorphism was evaluated.     

Synthesis of Cp-Re complexes via olefinic C-H activation and successive formation of cyclopentadienes

Treatment of an alpha,beta-unsaturated ketimine with an alpha,beta-unsaturated carbonyl compound in the presence of a rhenium complex, Re2(CO)10, gave a cyclopentadienyl-rhenium complex. This reaction proceeds via rhenium-catalyzed C-H bond activation of an olefinic C-H bond, insertion of an alpha,beta-unsaturated carbonyl compound into a Re-C bond of the alkenylrhenium intermediate, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline to give a cyclopentadiene derivative, followed by the formation of a cyclopentadienyl-rhenium complex from the cyclopentadiene derivative and the rhenium complex.     

Oxazaborolidinone-catalyzed enantioselective Diels-Alder reaction of acyclic alpha,beta-unsaturated ketones

allo-Threonine-derived O-acyl-B-phenyl-oxazaborolidinones are demonstrated to be powerful and highly enantioselective Lewis acid catalysts for the Diels-Alder reaction of simple acyclic enone dienophiles, expanding the scope of ketone dienophiles and dienes. With 10 to 20 mol % of catalyst, the Diels-Alder adducts are obtained in 76-98% ee with high endo-selectivity. The catalyst exhibits high activity for the reaction with the less reactive beta-substituted dienophiles and the less reactive 1,3-cycohexadiene and 1,3-butadiene derivatives. The application of the catalysts to the Diels-Alder reaction of furan is also described.     

Magnetic potassium clusters in a nanographite host system

The magnetism and structure for potassium clusters physisorbed in nanographite-based nanoporous host are investigated. Potassium clusters are subjected to a slight charge transfer to a host nanographite and modify the magnetism of the edge-state spins of nanographite. The localized spins of 4s electrons in the potassium cluster interact with each other through a strong antiferromagnetic interaction. Finite size effect and structural disorder around the cluster surface are responsible for anomalous spin fluctuations in the magnetism.     

Rhenium-catalyzed hydroamidation of unactivated terminal alkynes: synthesis of (E)-enamides

Reactions of cyclic amides with unactivated terminal alkynes in the presence of a catalytic amount of a rhenium complex provided (E)-enamides in high regio- and stereoselectivity (E:Z = >99:<1).     

Development of computer-assisted minimal-dose system with beam blanker for TEM

A computer-assisted minimal-dose system has been developed for the high-resolution observation of radiation-sensitive samples using a transmission electron microscope (TEM). This system consists of a CCD camera, a beam blanker and a control computer (PC) that also controls the TEM. A sample is illuminated by an electron beam only when the CCD camera takes images; otherwise, the beam blanker cuts off the electron beam. Emulated images, which are calculated from the images taken and the variable parameters of the TEM, such as magnification and sample stage position, are displayed on the control PC display. After a few times of repetition of exposures and emulations, the sample is positioned to final observation area. Subsequently to select the observation area, the system automatically adjusts the focus position from two different illuminating angle images and the TEM conditions are appropriate for taking a final image. The total electron dose before the final image is taken can be markedly decreased because the sample is irradiated by an electron beam only when images are taken. For the final image, a three-dimensional Fourier filtering method (3DFFM), which corrects the spherical aberration for the through-focus image series and enables the selection of the optimum focus condition later, is also included in our system.     

Studies on cardiotonic agents. IV. Synthesis of novel 1-(6,7-dimethoxy-4-quinazolinyl)piperidine derivatives carrying substituted hydantoin and 2-thiohydantoin rings

A series of novel 1-(6,7-dimethoxy-4-quinazolinyl)piperidines carrying substituted hydantoin and 2-thiohydantoin rings was synthesized and examined for cardiotonic activity in anesthetized dogs. Introduction of isopropyl and sec-butyl group at the 5-position of the hydantoin and thiohydantoin rings led to potent inotropic activity. Effects of insertion of an alkyl chain between the piperidine and the hydantoin rings were also examined. The structural requirements necessary for optimal cardiotonic activity within the series were investigated.