A novel method for preparation of 2-(methyl- or phehnylthio)alkanoic esters

Ethyl 2-acetylalkanoate gave ethyl 2-(methyl- or phenylthio)alkanoate in high yield on treatment wiht CH₃SSO₂CH₃, PhSSO₂Ph, or PhSSPh in the presence of small excess of EtONa in EtOH. Application of the present method to synthesis of pellitorine and the queen substance is also described.     

Kinetics and mechanism of the reduction of 1,10-phenanthroline—copper(II) complex

The cyclic voltammetric study of 1,10-phenanthroline—copper(II) complex was carried out in acidic buffer solution. It was found from the current—mole ratio (copper (II): 1,10-phenanthroline) relationship that the maximum coordination number of 1,10-phenanthroline—copper(II) complex was four under the present experimental condition. The reduction mechanism and kinetics of copper(II) was studied in the presence of various concentrations of 1,10-phenanthroline.     

Effect of the protonation level of poly(o-phenylenediamine) (PoPD) on the ac impedance of humidity-sensitive PoPD/poly(vinyl alcohol) composite film

A composite film consisting of poly(o-phenylenediamine) (PoPD) and poly(vinyl alcohol) (PVA) has been prepared, and the effect of the protonation level of PoPD on the response of the composite to humidity been investigated by ac impedance measurements. The electrochemical system of the PoPD/PVA composite in a humid atmosphere is represented by an electrochemical equivalent circuit containing film (R_film, C_film), Warburg (W) and interfacial (R_ct, C_dl) impedance. R_film was increased with decreasing protonation level of the PoPD in relative humidity regions higher than 40%, but it was almost independent of the protonation level in humidity regions lower than this percentage.     

Uptake of alkali and alkaline earth metal ions into electrochemically pretreated glassy carbon fibres by flow-through electrolysis

When glassy carbon fibres are used, alkali and alkaline earth metal ions are adsorbed in the micropores which are created or activated by oxidative treatment of the fibres. The average pore radius was estimated to be 2 nm by nitrogen adsorption experiments. Uptake was studied with a flow system consisting of a flow-through carbon-fibre electrode; a dropping mercury electrode at the end of the flow line monitored changes in the metal ion concentrations. The ions were taken up at negative potentials and released at positive potentials. The amount taken up increased in the sequence Na⁺ < Li⁺ < H⁺, suggesting that the ions were desolvated before entering the pore system.     

Photodynamic Efficiency of Protoporphyrin IX: Comparison of Endogenous Protoporphyrin IX Induced by 5-Aminolevulinic Acid and Exogenous Porphyrin IX

Abstract— Photodynamic efficiency of protoporphyrin IX (PP) accumulated in HeLa cells by the incubation of PP with HeLa cells was compared with that of accumulated PP formed from 5-aminolevulinic acid (ALA) as a precursor. The ALA-induced PP was photodynamically more efficient than exogenous PP. The difference is caused by monomelic PP concentration and PP localization site in HeLa cells. Exogenous PP was accumulated mainly in plasma membrane, and the membrane was strongly damaged by irradiation. The ALA-induced PP was selectively accumulated in mitochondria and inactivated the mitochondrial function by irradiation.     

KINETICS AND MECHANISM OF PHOTOCYCLOADDITION OF DEOXYURIDINES TO 2,3-DIMETHYL-2-BUTENE

The mechanism of photocycloaddition of 2′-deoxyuridine (1a) and thymidine (1b) to 2,3-dimethyl-2-butene (Bu) in acetonitrile by UV irradiation has been studied. The reciprocal quantum yield for the cycloaddition increased linearly with reciprocal concentrations of Bu in acetonitrile to give limiting quantum yields at infinite concentration of Bu as 0.030 and 0.0096 for 1a and 1b , respectively. This shows that the cycloaddition proceeds in a two-step mechanism between the triplet state of 1 and Bu through biradical intermediates. Addition of cis-1,3-pentadiene quenched the reaction obeying the Stern–Volmer equation. The above quenching experiments and laser transient spectroscopy revealed that the triplet state of 1a reacts with Bu with much larger rate constant (1.3–1.6 × 10⁹ M^?1 s^?1) than that of 1b (4–5 × 10⁷ M^?1 s^?1) reflecting larger steric hindrance exerted in the reaction of 1b than that of 1a .     

3,4-Thienylene-ethynylene Oligomers

Several well-defined 3,4-thienylene-ethynylene oligomers with different chain lengths have been synthesized and characterized. X-Ray crystallographic analyses proved their unique, totally helical conformations.     

A SYNTHETIC ROUTE TO 3-METHYLTHIO-2-ALKANONES STARTING FROM 3-ALKYL-2,4-PENTANEDIONES

Abstract

An efficient preparation of a 3-methylthio-2-alkanone (1) has been realized by the reaction of a 3-alkyl-2,4-pentanedione (8) with one mol-equiv of S-methyl methanethiosulfonate (4) in the presence of excess EtONa in EtOH. Furthermore, treatment of 8 with 4 and K₂CO₃ in refluxing acetone, followed by addition of MeOH and heating the resulting mixture, gave 1 in a high yield. These methods were applied to synthesis of pseudoionone.     

Inclusion of Poly(ethylene glycol)s by Crystalline (R)-(1-Naphthyl)glycyl-(R)-phenylglycine

Abstract

Crystallization of (R)-(1-naphthyl)glycyl-(R)-phenyl-glycine [(R,R)-1] in the presence of oligo(ethylene glycol) dimethyl ethers 2(n) or poly(ethylene glycol)s (PEGs, 3(M_n )) afforded inclusion compounds. The ratio of (R,R)-1/the guest polymer (2 or 3) was proportional to the length of the polymer chain. The crystal structure of a hepta(ethylene glycol) dimethyl ether-included compound was disclosed by X-ray crystallography which showed that (R,R)-1 molecules form a sheet and the guest molecule penetrates the crystal lattice of (R,R)-1 through a one-dimensional channel on the sheet. Powder X-ray analysis revealed that, regardless of the length of the guest polymer, the distance between the neighboring sheets remains unchanged (12.0–12.3 Å) in these inclusion crystals. By thermal analysis, it was shown that the decomposition points of these inclusion compounds became higher with the longer PEG included. The inclusion phenomenon enabled the fractionation of PEGs with various molecular weights, among which longer PEG was preferably included.     

Pyrolysis of Dibenzyl Selenides to Bibenzyls

The formation of carbon-carbon bond by sulfur extrusion such as pyrolysis of cyclic sulfones is well known as an important synthetic method, especially for the synthesis of cyclophane framework.¹⁾ Little is known about selenium extrusion as the counterpart, though organoseleniums have been properly appreciated as a useful tool for manipulating a functional group.²⁾ Lardon reported that the thermal decomposition of dibenzyl diselenide led to a mixture of dibenzyl selenide and polyselenides.³⁾ In contrast, recent reports showed that at 210°C, heating bis(diphenylmethyl) diselenide resulted in ready selenium extrusion to 1,1,2,2-tetraphenylethane⁴⁾, and dianthrylmethyl mono- and diselenides to 1,2-dianthrylethane.⁵⁾ Therefore,- it is worthwhile to study the thermal behavior of dibenzyl selenide itself.