Photocatalyzed ortho‐Alkylation of Pyridine N‐Oxides through Alkene Cleavage

A photocatalyzed reaction of pyridine N‐oxides with alkenes gives ortho‐alkylated pyridines with cleavage of the carbon–carbon double bond. Benzyl and secondary alkyl groups are incorporated at the ortho position of pyridines in one pot.     

Turn-on fluorescence sensor for mono- and di-phosphonic acid derivatives using anthracene-based diamidine and its detection of amidinium-phosphonate and amidinium formation

The fluorescence detection of di-phosphonic acid and mono-phosphonic acid derivatives using the anthracene-based diamidine 1 has been investigated. The diamidine 1 forms 1:1 and 1:2 complexes with the di-phosphonic acid and mono-phosphonic acid derivatives, respectively, and showed a blue fluorescence (λ_em = 432–442 nm) in a DMSO solution. The formation of amidinium-phosphonate (complex formation) and dissociated amidinum (λ_em = 468 nm as a broad band) were distinguished by the difference in the fluorescence wavelength, and confirmed by DOSY NMR spectroscopy and TD-DFT calculations. The formation of a 1:2 complex with diamidine 1 and methylphosphonic acid having additional intermolecular hydrogen-bonding between the methylphosphonic acids is proposed.     

Lithium ion phase-transfer reaction at the interface between the lithium manganese oxide electrode and the nonaqueous electrolyte

The lithium ion phase-transfer reaction between the spinel lithium manganese oxide electrode and a nonaqueous electrolyte was investigated by the ac impedance spectroscopic method. The dependence of the impedance spectra on the electrochemical potential of the lithium ion in the electrode, the lithium salt concentration in the electrolyte, the kind of solvent, and the measured temperature were examined. Nyquist plots, obtained from the impedance measurements, consist of two semicircles for high and medium frequency and warburg impedance for low frequency, indicating that the reaction process of two main steps for high and medium frequency obey the Butler-Volmer type equation and could be related to the charge-transfer reaction process accompanied with lithium ion phase-transfer at the interface. The dependency on the solvent suggests that both steps in the lithium ion phase-transfer at the electrode/electrolyte interface include the desolvation process and have high activation barriers.     

Indium(III) chloride-promoted intramolecular addition of allylstannanes to alkynes

In the presence of an equimolar amount of InCl(3), 8-tributylstannyl-6-octen-1-ynes (allylstannanes bearing an alkynyl group) were efficiently cyclized to 2-allyl-1-methylenecyclopentanes. In contrast, catalytic use of InCl(3) gave 2-allyl-1-(tributylstannylmethylene)cyclopentanes mainly by intramolecular allylstannylation. These cyclizations could proceed via intramolecular addition of an allylindium intermediate.     

Total synthesis and complete configurational assignment of amphirionin-2

Amphirionin-2 is a linear polyketide metabolite that exhibits potent and selective cytotoxic activity against certain human cancer cell lines. We disclose herein the first total synthesis of amphirionin-2 and determination of its absolute configuration. Our synthesis featured an extensive use of cobalt-catalyzed Mukaiyama-type cyclization of γ-hydroxy olefins for stereoselective formation of all the tetrahydrofuran rings found in the natural product, and a late-stage Stille-type coupling for convergent assembly of the entire carbon backbone. Four candidate diastereomers of amphirionin-2 were synthesized in a unified, convergent manner, and their spectroscopic/chromatographic properties were compared with those of the authentic material. The present study culminated in the reassignment of the C5/C7 relative configuration, assignment of the C12/C18 relative configuration, and determination of the absolute configuration of amphirionin-2.

An extensive application of cobalt-catalyzed Mukaiyama-type cyclization of γ-hydroxy olefins and a late-stage Stille-type reaction enabled syntheses of four diastereomers of amphirionin-2 to establish its absolute configuration.     

The first isolation of allenylselenonium salts: their synthesis and properties as electrophiles

The first synthesis of allenylselenonium salts and their reactivities are described. The corresponding allenyl methyl selenides were alkylated with methyl trifluoromethanesulfonate to afford the desired compounds. Their reactions with active methylene carbanions produced furan, dihydrofuran or methylene cyclopropane derivatives via the Michael addition of nucleophiles to the selenonium salts.     

High-performance liquid chromatographic method for monitoring leupeptin in mouse serum and muscle by pre-column fluorescence derivatization with benzoin

A high-performance liquid chromatographic method is described for the determination of leupeptin, a possible therapeutic drug for muscular dystrophy, in mouse serum and muscle. Leupeptin is reduced with sodium borohydride to leupeptinol, and then converted to a fluorescent derivative with benzoin. The derivative is separated on a reversed-phase column (LiChrosorb RP-18) with isocratic elution and determined with fluorescence detection. The detection limits of leupeptin in serum and muscle are 250 pmol/ml (107 ng/ml) and 500 pmol/g (214 ng/g), respectively, corresponding to approximately 150 fmol each in a 100-microliters injection volume. This method is simple and sensitive enough to permit the quantification of leupeptin in biological samples from mice dosed with leupeptin.     

Ketone synthesis by intramolecular acylation of organorhodium(I) with ester

New cyclization reactions forming cyclic ketones were developed wherein an intermediate organorhodium(I) species underwent intramolecular acylation with an ester group. A 2-norbornanone skeleton is constructed in a single operation through successive multiple carbon-carbon bond formation. The reactions ended up with generation of an alkoxyrhodium(I) species to promote the next catalytic cycle.     

Highly-efficient metal-free organic dyes for dye-sensitized solar cells

A solar-to-electric conversion efficiency of 6.1% is achieved with this new dye, compared to 6.3% for N3 dye under the same experimental conditions. Although these indoline dyes are slightly less efficient than N3 dye, the cost of indoline dye is much less than for N3 due to ease of preparation. Furthermore, indoline dyes are shown to be highly stable to photoredox processes by cyclic voltammogram.     

Characterization of diffusion-controlled mass transport through nanoporous and nanothin films plasma polymerized on a sputtered platinum electrode

We demonstrate the diffusion mode of various redox chemical species through a plasma-polymerized nanothin coating with nanometer-sized pores on a sputtered platinum (Pt) electrode. In this work, hexamethyldisiloxane plasma-polymerized films (PPFs) were added onto the sputtered platinum film, both of which were sequentially deposited in the same vacuum chamber. Results of atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemical studies showed that the PPF provided the platinum electrode with a coating with a complete surface coverage. Sub-nanometer-sized pores (less than 1 nm) responsible for a highly crosslinked polymer network in the PPF coatings offered diffusivity-controlled permeation of redox molecules (i.e., size-exclusivity) rather than solubility-controlled permeation (i.e., chemoselectivity). Consequently, variation of the plasma power could give control over the size of the nanometer-sized cavities.