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.     

Development of modulated rf sequences for decoupling and recoupling of nuclear-spin interactions in sample-spinning solid-state NMR: application to chemical-shift anisotropy determination

An approach to design modulated rf sequences under sample spinning which decouple/recouple a specific nuclear-spin interaction in solid-state NMR is presented. The Euler angles of the spin rotation caused by a general rf field are forced to fulfill the symmetry principle theory for selecting an interaction of interest. Then, modulated rf sequences are directly obtained from the Euler angles with a large degree of freedom. rf sequences with high performance can be selected from them by numerically optimizing rf sequence parameters. As an example of this approach, an amplitude- and phase-modulated rf sequence to recouple chemical-shift anisotropy (CSA) is developed, which is robust with respect to rf inhomogeneity. Two-dimensional (2D) experiments with this rf sequence under on and off magic-angle spinning (MAS) provide one-dimensional and 2D powder patterns, respectively. The latter enables us to determine the CSA principal values more accurately even for overlapped signals in MAS spectra. The effectiveness of this modulated rf sequence is experimentally demonstrated on [(15)N]-N-acetyl-D,L-alanine for determination of the (15)N and (13)CO CSA principal values.     

Apparent increase of insulin peak area in HPLC analysis of a preparation consisting of a mixture of insulin and total parenteral nutrition

The peak area of insulin in a mixture of K.C.L. injection and hyperalimentation fluid was found to increase in a time dependent manner up to 24 h in measurement by a high-performance liquid chromatograph. The increase of peak area corresponding to the insulin was detected at wavelengths of both 210 and 280 nm. This increase was only observed in the presence of the sugars, tryptophan, riboflavin, and insulin, and ascorbate was shown to counteract the increase. These results suggest the possibility that insulin forms a mixture caused by the oxidation reaction in a hyperalimentation fluid.     

Through-space conjugated polymers based on cyclophanes

Conjugated polymers display unique electronic and optical properties, which favor their use in applications as optoelectronic materials and molecular devices. Despite the recent remarkable progress in the chemistry of conjugated polymers, the synthesis of conjugated polymers containing cyclophane units in the main chain is limited to only a few examples. This Minireview presents recent developments in the synthesis, properties, and applications of through-space conjugated polymers based on cyclophanes.     

Zeolite LTA Nanoparticles Prepared by Laser-Induced Fracture of Zeolite Microcrystals

Zeolite LTA nanoparticles are prepared by laser-induced fragmentation of zeolite LTA microparticles using a pulsed laser. Zeolite nanoparticle formation is attributed to absorption of the laser at impurities or defects within the zeolite microcrystal generating thermoelastic stress that mechanically fractures the microparticle into smaller nanoparticle fragments. Experimentally, it is found that nanoparticles have a wide size and morphology distribution. Large nanoparticles (>200 nm) are typically irregularly shaped crystals of zeolite LTA, whereas small nanoparticles (<50 nm) tend to be spherical, dense, and amorphous, indicative of destruction of the original LTA crystal structure. Results of the fragmentation versus laser parameters show that shorter laser wavelengths are more efficient at producing zeolite nanoparticles, which is explained based on a larger cross section for optical absorption in the zeolite crystal. Increasing the laser energy density irradiating the sample was found to be a trade-off between increasing the amount of fragmentation and increasing the amount of structural damage to the zeolite crystal. It is suggested that in the presence of strongly absorbing defects, plasma formation is induced resulting in dramatically higher temperatures. On the basis of these results it is suggested the optimal laser processing conditions are 355 nm and 10 mJ/pulse laser energy for our LTA samples.     

Preparation of CF3-containing 1,3-di- and 1,1,3-trisubstituted allenes

Novel synthetic pathway to access trifluoromethylated allenes with 1,3-di- as well as 1,1,3-trisubstitution patterns was developed from a variety of 4,4,4-trifluorobut-2-yn-1-ols which were then transformed into the corresponding vinylic iodides in highly regio- and stereospecific manners, and zinc-mediated beta-elimination after trifluoroacetylation of the hydroxyl group eventually realized the formation of the target molecules in good to excellent overall yields in facile and short steps.     

Catalytic enantioselective Friedel-Crafts/Michael addition reactions of indoles to ethenetricarboxylates

[reaction: see text] The Friedel-Crafts reaction is an important reaction for the formation of new C-C bonds. Recently, catalytic enantioselective Friedel-Crafts reaction of alkylidene malonates has been reported. However, the substituents in alkylidene malonates are limited. To explore new substituents such as carboxyl and carbonyl groups, catalytic enantioselective Friedel-Crafts reactions of reactive ethenetricarboxylates and acyl-substituted methylenemalonates 1 were investigated. The reaction of 1 with indoles in the presence of catalytic amounts of chiral bisoxazoline copper(II) complex (10%) in THF at room temperature gave alkylated products in high yields and up to 95% ee. The enantioselectivity can be explained by the secondary orbital interaction on approach of indole to the less hindered side of the 1-Cu(II)-ligand complex.     

Facile synthesis of aryl ether dendrimer from unprotected AB2 building blocks using thionyl chloride as an activating agent

[structure: see text] A novel, rapid, inexpensive, and highly efficient convergent approach for the synthesis of a Fréchet- type aryl ether dendrimer using thionyl chloride has been developed. In this method, the purification of each dendron and a dendrimer occurs by recrystallization, extraction, and precipitation. The MALDI-TOF MS spectrum supported the formation of the G2, G3, and G4 dendrons and the star-shaped G4 dendrimer.     

Synthesis and characterization of Dithia[3.3](2,6)pyridinophane-containing polymers: application to the palladium-catalyzed Heck reaction

[reaction: see text] We synthesized zigzag polymers consisting of dithia[3.3](2,6)pyridinophane units that were flipped rapidly as a result of syn-[anti]-syn isomerization. Pyridinophane units were fixed in the syn form by complexation with palladium, and the resulting polymer complex exhibited a high catalytic activity for the Heck coupling reaction.     

Phase synchronization between collective rhythms of globally coupled oscillator groups: noiseless nonidentical case

We theoretically study the synchronization between collective oscillations exhibited by two weakly interacting groups of nonidentical phase oscillators with internal and external global sinusoidal couplings of the groups. Coupled amplitude equations describing the collective oscillations of the oscillator groups are obtained by using the Ott-Antonsen ansatz, and then coupled phase equations for the collective oscillations are derived by phase reduction of the amplitude equations. The collective phase coupling function, which determines the dynamics of macroscopic phase differences between the groups, is calculated analytically. We demonstrate that the groups can exhibit effective antiphase collective synchronization even if the microscopic external coupling between individual oscillator pairs belonging to different groups is in-phase, and similarly effective in-phase collective synchronization in spite of microscopic antiphase external coupling between the groups.