Enantioseparation of doubly functionalized polar norbornenes by HPLC and their ruthenium‐catalyzed ring‐opening metathesis polymerization

Doubly fuctionalized polar norbornenes bearing the cyano and ester groups in 2,3‐positions are synthesized and enantiomers are separated by high performance liquid chromatography (HPLC) with a chiral stationary phase. These optically active monomers are polymerized by ruthenium carbene catalysts, and high yields of the polymers were obtained. The chiral monomer bearing ethyl ester gave an optically active polymer of lower, but opposite sign of optical rotation (monomer [α]_D = +61.0°, polymer [α]_D = ?3.1°). The circular dichroism (CD) of the obtained chiral polymers gave a Cotton effect. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 485–491, 2010     

Syntheses, characterization, and catalytic ability in alkane oxygenation of chloro(dimethyl sulfoxide)ruthenium(II) complexes with tris(2-pyridylmethyl)amine and its derivatives

New ruthenium(II) complexes having a tetradentate ligand such as tris(2-pyridylmethyl)amine (TPA), tris[2-(5-methoxycarbonyl)pyridylmethyl]amine [5-(MeOCO)3-TPA], tris(2-quinolylmethyl)amine (TQA), or bis(2-pyridylmethyl)glycinate (BPG) have been prepared. The reaction of the ligand with [RuCl2(Me2SO)4] resulted in a mixture of trans and cis isomers of the chloro(dimethyl sulfoxide-kappaS)ruthenium(II) complexes containing a TPA or a BPG, whereas a trans(Cl,N(amino)) isomer was selectively obtained for 5-(MeOCO)3-TPA and TQA. The trans and cis isomers of the [RuCl(TPA)(Me2SO)]+ complex were easily separated by fractional recrystallization. The molecular structures of trans- and cis(Cl,N(amino))-[RuCl(TPA)(Me2SO)]+ complexes and the trans(Cl,N(amino))-[RuCl{5-(MeOCO)3-TPA}(Me2SO)]+ complex have been determined by X-ray structural analyses. The reaction of TPA with [RuCl2(PhCN)4] gave a single isomer of the chloro(benzonitrile)ruthenium(II) complex, whereas the bis(benzonitrile)ruthenium(II) complex was obtained with BPG. The cis(Cl,N(amino))-[RuCl(TPA)(Me2SO)]+ complex is thermodynamically much less stable than the trans isomer and isomerizes in dimethyl sulfoxide at 65-100 degrees C. Oxygenation of alkanes catalyzed by these ruthenium(II) complexes has been examined. The chloro(dimethyl sulfoxide-kappaS)ruthenium(II) complexes with TPA and its derivatives using m-chloroperbenzoic acid as a cooxidant showed high catalytic ability. Adamantane was efficiently and selectively oxidized to give 1-adamantanol up to 88%. The chloro(dimethyl sulfoxide-kappaS)ruthenium(II) complex with 5-(MeOCO)3-TPA was found to be the most active catalyst among the complexes examined.     

2,7-Diphenyl[1]benzothieno[3,2-b]benzothiophene, a new organic semiconductor for air-stable organic field-effect transistors with mobilities up to 2.0 cm2 V(-1) s(-1)

Vapor-deposited thin films of a newly developed sulfur-containing heteroarene, 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DPh-BTBT), were used as an active layer of OFETs, which showed excellent FET characteristics in ambient conditions with mobilities of approximately 2.0 cm2 V-1 s-1 and Ion/Ioff of 107.     

Synthesis,characterization, and thermal properties of ring‐opening metathesis polynorbornenes and their hydrogenated derivatives bearing various ester and cyano groups

Doubly functionalized polar norbornenes 3a – 3g substituted by both a variety of ester and cyano groups were polymerized by ring‐opening metathesis polymerization (ROMP) with a Ru carbene complex 2 bearing 3‐bromopyridine as a ligand (third generation Grubbs' catalyst) in a living manner. The successive hydrogenation of the main‐chain double bond in the synthesized living ROMP polymers 4a – 4g with a hydridoruthenium complex was exploited. The comparison of thermal properties of a series of ring‐opening metathesis polymers 4a – 4g with those of their hydrogenated derivatives 5a – 5g revealed the decrease of glass transition temperatures (T_g) but little change of the 5% decomposition temperature (T_d⁵). In all cases examined in this study, a decrease of T_g by hydrogenation was around 20–40 °C, regardless of the ester substitutents. In the presence of the additional PCy₃, triethylamine, and methanol after complete consumption of monomer 3a under the living ROMP condition, the tandem ROMP‐hydrogenation of the resulting polymer 4a generated in situ was attained under a H₂ (9.8 MPa) atmosphere at 80 °C to afford the hydrogenated polymer 5a , retaining the narrow polydispersity of 1.03. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3314–3325 2008     

Feedback control of instability waves in a transitional flat-plate boundary layer

A semi-automatic and active control of T-S waves and oblique waves in a transitional flat plate boundary layer is carried out in a wind-tunnel experiment and a numerical simulation. An array of piezo-ceramic actuators attached on a surface is used to generate counter waves that cancel the incoming instability waves. The actuator’s operating amplitudes and phases are successively updated using the velocity fluctuations monitored downstream by a rake of hotwires. Experimental results show that the system is effective in weakening these waves when their inclination angles are less than 15 degrees. However, the system encountered difficulty in controlling the waves of large inclination angles. In the numerical simulation, it is shown that the control can be accomplished much easier. The numerical results show that controllability of the large inclination angle waves can be improved by shortening the spanwise length each actuator piece. The danger of pursuing this kind of research solely by a numerical simulation is pointed out.     

High-Sensitivity Two-Dimensional Observation of Thermal Birefringence Compensation in Laser-Diode Pumped Nd: Glass Laser Rods

We measured the two-dimensional birefringence compensation in laser-diode (LD) pumped Nd:glass (HAP4) laser rods with a high-sensitivity polarimeter. The compensation was performed by inserting a 90° quartz rotator between two identical LD pumped Nd:glass rods with conductive cooling. A considerable reduction of birefringence loss from 9.8% to less than 0.9% after compensation was observed.     

Efficient charge generation and collection in organic solar cells based on low band gap dyad molecules

Low band gap dyad molecules were prepared that have absorption spectra matched well with the solar spectrum, and the construction of efficient charge transport pathways was observed. Under AM 1.5 illumination, the devices have achieved the highest J(SC) (4.79 mA cm(2)) and FF (0.46) in dyad-based organic solar cells to date.     

Tailor-Made Amino Acids and Fluorinated Motifs as Prominent Traits in Modern Pharmaceuticals

Structural analysis of modern pharmaceutical practices allows for the identification of two rapidly growing trends: the introduction of tailor-made amino acids and the exploitation of fluorinated motifs. Curiously, the former represents one of the most ubiquitous classes of naturally occurring compounds, whereas the latter is the most xenobiotic and comprised virtually entirely of man-made derivatives. Herein, 39 selected compounds, featuring both of these traits in the same molecule, are profiled. The total synthesis, source of the corresponding amino acids and fluorinated residues, and medicinal chemistry aspects and biological properties of the molecules are discussed.     

Total syntheses of makaluvamines A, B, C, D and E, cytotoxic pyrroloiminoquinone alkaloids isolated from marine sponge bearing inhibitory activities against topoisomerase II

Syntheses of makaluvamines A, B, C, D and E (1 – 5), new members of tetrahydropyrroloiminoquinone alkaloids, have been successfully carried out. Particularly, olefin introduction for makaluvamines B and E could be achieved by Pd - mediated and E₂ type methodologies.     

Unusual behavior of nuclear relaxation in CeCu2Si2 “possible evidence for triplet superconductivity”

Nuclear relaxation of ⁶³Cu in the superconducting state of the Kondo-lattice system CeCu₂Si₂ has been studied with the use of the ⁶³Cu nuclear quadrupole resonance technique under zero field and down to 65mK. The nuclear spin-lattice relaxation rate (1/T₁) decreases drastically just below T_c=0.67 K down to 0.5T_c without the apparent enchanced behavior and then is found to be almost temperature independent below 0.3T_c. These results suggest that the superconductivity in CeCu₂Si₂ is not in the usual BCS regime. The analysis based upon the existing triplet pairing model with an anisotropic energy gap describes well the behavior from T_c down to 0.5T_c, while the temperature independence below 0.3T_c remains unexplained.