Integrated electrochemical-chemical oxidation mediated by alkoxysulfonium ions

Generation of carbocations by the "cation pool" method followed by reaction with dimethyl sulfoxide (DMSO) gave the corresponding alkoxysulfonium ions. Alkoxysulfonium ions could also be generated by in situ DMSO trapping of electrochemically generated carbocations. The resulting alkoxysulfonium ions were transformed into carbonyl compounds by treatment with triethylamine. The present integrated electrochemical-chemical oxidation can be applied to the oxidation of diarylmethanes to diaryl ketones, toluenes to benzaldehydes, and aryl-substituted alkenes to 1,2-diketones. Moreover, the oxidation of unsaturated compounds bearing a nucleophilic group in an appropriate position gives cyclized carbonyl compounds.     

Organic reactions mediated by electrochemically generated ArS+

Low-temperature electrochemical oxidation of ArSSAr was carried out to generate a pool of "ArS(+)". Spectroscopic studies ((1)H NMR and CSI-MS) of the resulting solution revealed the accumulation of ArS(ArSSAr)(+). The resulting "ArS(+)" pool reacted with alkenes and alkynes to give diarylthio-substituted products. The "ArS(+)" pool rapidly reacted with thioacetals to give the corresponding alkoxycarbenium ion pools, which reacted with various carbon nucleophiles (indirect cation pool method). The reaction of the alkoxycarbenium ion pools with stilbene derivatives in the presence of ArSSAr gave thiochroman derivatives. In addition to such stoichiometric reactions, a catalytic amount of "ArS(+)" serves as an initiator and a chain carrier of some cationic chain reactions involving intramolecular carbon-carbon bond formation. In situ generation of "ArS(+)" by electrochemical oxidation of ArSSAr with a catalytic amount of electricity in the presence of a substrate is also effective for such cationic chain reactions.     

Enhanced catalytic activity on titanosilicate molecular sieves controlled by cation-π interactions

A new class of heterogeneous catalytic systems utilizing cation-guest interactions was designed based on microporous titanosilicate molecular sieves. Introducing heavier alkali metal cations on ion-exchange sites of the framework resulted in a significant enhancement of the catalytic activity for oxidation of cyclohexene and styrene, whereas such an enhancement was not observed in oxidation of cyclohexane without π systems. Distinct relationships between the catalytic activities and intermolecular interaction energies which were determined by IR spectroscopic and computational approaches clearly evidenced the predominance of the cation-π interaction in this catalytic system.     

Aromatic character of polycyclic π systems formed by fusion of two or more rings of the same size

The sequential line plot of topological resonance energy (TRE) against the number of π electrons (N(π)) for any polycyclic aromatic hydrocarbon (PAH) is very similar with the same number of extrema to that for benzene. Thus, global aromaticity of a PAH molecular ion strongly reflects that of a benzene molecular ion. Likewise, the N(π) dependence of TRE for any polycyclic π system formed by fusion of two or more rings of the same size reflects that for a monocyclic species of the same ring size. In general, TREs for such polycyclic π systems and their molecular ions can be interpreted consistently by reference to those for neutral and charged monocyclic species of the same ring size.     

He I ultraviolet photoelectron spectroscopy of benzene and pyridine in supersonic molecular beams using photoelectron imaging

We performed He I ultraviolet photoelectron spectroscopy (UPS) of jet-cooled aromatic molecules using a newly developed photoelectron imaging (PEI) spectrometer. The PEI spectrometer can measure photoelectron spectra and photoelectron angular distributions at a considerably higher efficiency than a conventional spectrometer that uses a hemispherical energy analyzer. One technical problem with PEI is its relatively high susceptibility to background electrons generated by scattered He I radiation. To reduce this problem, we designed a new electrostatic lens that intercepts background photoelectrons emitted from the repeller plate toward the imaging detector. An energy resolution (ΔE/E) of 0.735% at E = 5.461 eV is demonstrated with He I radiation. The energy resolution is limited by the size of the ionization region. Trajectory calculations indicate that the system is capable of achieving an energy resolution of 0.04% with a laser if the imaging resolution is not limited. Experimental results are presented for jet-cooled benzene and pyridine, and they are compared with results in the literature.     

Location of [60]fullerene incorporation in lipid membranes

We confirmed that most C(60) fullerene units are located in the hydrophobic core of the lipid bilayer membrane in water-soluble lipid membrane incorporated C(60) (LMIC(60)) complexes using differential scanning calorimetry (DSC) and (13)C NMR spectra in the presence of radical labels.     

Fluorescent trimethyl-substituted naphthyridine as a ligand for C-C mismatch detection in CCG trinucleotide repeats

We report on the selective binding of 2-amino-5,6,7-trimethyl-1,8-naphthyridine (ATMND) to C-C mismatch present in the hairpin structures of (CCG)(n) trinucleotide repeats that are associated with neurological diseases; this binding is accompanied by significant fluorescence quenching of ATMND.     

Photoresponsive liposomal nanohybrid cerasomes

An innovative photoresponsive cerasome is fabricated by sol-gel process in combination of self-assembly technique from a molecularly designed organoalkoxysilylated lipid containing an azobenzene unit, which is able to operate as a "valve" with an "on-off" function under specific stimuli to control the release of loaded guest molecules from the liposomal membrane.     

Spatiotemporally controlled contraction of micropatterned skeletal muscle cells on a hydrogel sheet

We have developed gel sheet-supported C(2)C(12) myotube micropatterns and combined them with a microelectrode array chip to afford a skeletal muscle cell-based bioassay system. Myotube line patterns cultured on a glass substrate were transferred with 100% efficiency to the surface of fibrin gel sheets. The contractile behavior of each myotube line pattern on the gel was individually controlled by localized electrical stimulation using microelectrode arrays that had been previously modified with electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT). We successfully demonstrated fluorescent imaging of the contraction-induced translocation of the glucose transporter, GLUT4, from intracellular vesicles to the plasma membrane of the myotubes. This device is applicable for the bioassay of contraction-induced metabolic alterations in a skeletal muscle cell.     

All-Fiber Optical Add-Drop Multiplexer Using a Pair of Fiber Grating Couplers

A new all-fiber optical add-drop multiplexer (ADM) using a pair of fiber grating couplers (FGCs) was proposed and first demonstrated. It was theoretically and experimentally shown that both drop and add efficiencies could be maximized in the proposed ADM. It was also clarified that the crosstalk between dropped and added signals could be improved in the proposed ADM compared with that in the single FGC. Drop and add operations in the ADM for 3-channel WDM signals with 1.6 nm wavelength spacing were confirmed. The ADM with signal amplification ability, which consists of a pair of FGCs, an EDF, and a pump-LD, was proposed and demonstrated. It was confirmed that the dropped and transmitted optical signals could be amplified in the ADM, and would be able to expand fiber routing spans.