Chemically-induced geometrical isomerization of stilbenes during peroxyoxalate chemiluminescence reaction: revisit to ‘photochemistry without light’

The chemically-induced isomerization of stilbenes during the peroxyoxalate chemiluminescence (PO-CL) reactions was reinvestigated. The PO-CL reactions using bis(2,4,6-trichlorophenyl) oxalate in the presence of several stilbenes (type A reaction) produced cis-stilbenes in 0–4% yields, which was dependent on the singlet excitation energy of the stilbenes. On the other hand, the PO-CL reactions of the oxalates, containing the stilbene moieties in the molecules (type B reaction), produced cis-stilbenes 0–9.3% yields, some of which were much more effective than the type A reactions considering the amount of the oxalate moiety as the energy supplier.     

Solvent-free asymmetric conjugate addition of malonates to enones using a diaminomethylenemalononitrile organocatalyst

Diaminomethylenemalononitrile organocatalyst 1 efficiently promotes the asymmetric conjugate addition of malonates to α,β-unsaturated ketones to afford the corresponding addition products in high to excellent yields with up to 98% ee.     

Efficient generation and trapping of acylbenzynes from hypervalent iodine compounds

[5-Acyl-2-(trimethylsilyl)phenyl]iodonium triflates were prepared for the generation of benzynes bearing ketone function. Treatment of the iodonium triflates with Bu₄NF in CH₂Cl₂ in the presence of furan at room temperature gave 6-acyl-1,4-epoxy-1,4-dihydronaphthalenes in high yields. The mild conditions and the tolerance of the ketone function on benzyne generation are attributable to the advantage of hypervalent iodine compounds.     

Investigation of polycondensation through the copolycondensation of preformed oligomers and bisphenols by a two‐stage solution reaction with tosyl chloride,dimethylformamide, and pyridine

A two‐stage copolycondensation of an equimolar mixture of isophthalic acid and terephthalic acid first with a bisphenol (BP) and then with another BP was carried out with a tosyl chloride/dimethylformamide/pyridine condensing agent. When the preformed oligomers from a BP with no substituent or a methyl substituent were allowed to react with another BP comonomer containing polar SO₂, CO, or Cl groups, the copolycondensation was significantly promoted. Such effects were absent with the unsubstituted BP and the methyl derivative. In addition, during the reaction of oligomers from BPs with polar groups, a similarly polar BP did not react so effectively, and the unsubstituted BP did not have any effect on the copolycondensation. On the basis of the sequence distributions for the resultant copolymers determined by ¹H NMR, it was likely that the copolycondensation could be promoted when the second comonomers were randomly distributed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4024–4031, 2002     

Photothermal reshaping of gold nanorods depends on the passivating layers of the nanorod surfaces

Photothermal reshaping of gold nanorods was triggered by pulsed-laser irradiation. The efficiency of the reshaping was strongly dependent on the surface conditions of the gold nanorods. When the gold nanorods were dispersed in concentrated hexadecyltrimethylammonium bromide (CTAB), the gold nanorods were efficiently transformed into a phi-shape. By comparison when poly(styrene sulfonate), poly(vinylpyrrolidone), poly(ethylene glycol), or phosphatidylcholine layers were used, the CTAB layers were found to be a better thermal insulator that helped to enhance the photothermal reshaping of the gold nanorods.     

Spectrophotometric determination of spermine and related compounds using o-hydroxyhydroquinonephthalein and manganese(II).

A simple and highly sensitive spectrophotometric method for the determination of spermine (Spm) was established based on the ternary complex formation reaction of Spm with o-hydroxyhydroquinonephthalein (QP) as a xanthene dye and manganese(II) as a metal ion in the presence of a dispersion agent. The apparent molar absorptivity at 555 nm and the relative standard deviation of the proposed method were 1.4 x 10(5) dm(3) mol(-1) cm(-1) and 0.50% (n = 10), respectively. In the method for flow-injection analysis (FIA), which employs a single-channel flow manifold system, a good linear relationship was observed over the 2 - 20 pg microl(-1) range of Spm by direct injection.     

Simultaneous quantitation of sphingoid bases and their phosphates in biological samples by liquid chromatography/electrospray ionization tandem mass spectrometry

We developed a liquid chromatography/electrospray ionization tandem mass spectrometry method for the simultaneous quantitative determination of C18 sphingosine (Sph), C18 dihydrosphingosine (dhSph), C18 phytosphingosine (pSph), C18 sphingosine-1-phosphate (S1P), C18 dihydrosphingosine-1-phosphate (dhS1P), and C18 phytosphingosine-1-phosphate (pS1P). Samples were prepared by simple methanol deproteinization and analyzed in selected reaction monitoring modes. No peak tailing was observed on the chromatograms using a Capcell Pak ACR column (1.5 mm i.d. × 250 mm, 3 μm, Shiseido). The calibration curves of the sphingoids showed good linearity (r > 0.996) over the range of 0.050-5.00 pmol per injection. The accuracy and precision of this method were demonstrated using four representative biological samples (serum, brain, liver, and spleen) from mice that contained known amounts of the sphingoids. Samples of mice tissue such as plasma, brain, eye, testis, liver, kidney, lung, spleen, lymph node, and thymus were examined for their Sph, dhSph, pSph, S1P, dhS1P, and pS1P composition. The results confirmed the usefulness of this method for the physiological and pathological analysis of the composition of important sphingoids.     

Efficient use of a surfactant for copper-catalyzed coupling reaction of arylboronic acids with imidazoles in water

Copper-catalyzed oxidative coupling of arylboronic acids with imidazoles in water was realized by using an amphiphilic surfactant. By choosing an appropriate surfactant, reactions of a variety of arylboronic acids proceeded smoothly under mild and base-free conditions, providing an efficient, practical, and greener method for the synthesis of N-arylimidazoles.     

Symmetric extensions of dihedral quandles and triple points of non-orientable surfaces

Quandles with involutions that satisfy certain conditions, called good involutions, can be used to color non-orientable surface-knots. We use subgroups of signed permutation matrices to construct non-trivial good involutions on extensions of odd order dihedral quandles.For the smallest example of order 6 that is an extension of the three-element dihedral quandle R₃, various symmetric quandle homology groups are computed, and applications to the minimal triple point number of surface-knots are given.