Novel method for synthesis of aryl hydrazones from α-diazo esters: scope and limitations of nucleophiles

Aryl hydrazones, the precursor of Fischer indole synthesis, were easily obtained by nucleophilic addition of aryllithium reagents to diazo esters. The aryl hydrazones were converted into indoles in good yields by heating with thionyl chloride in alcohol. Grignard reagent was also a good nucleophile, whereas organozinc reagent did not react with diazo esters. Aryllithium reagents were prepared by reacting aryl bromides having various substitutions at 2-, 3-, 4-, or multi positions with n-BuLi. The addition of nucleophiles derived from bromopyridines to diazo esters also gave hydrazones.     

Studies of the amorphous region of polymers. II. Relationship between change of structure and glass-transition temperature in polycarbonate

A study of the effect of drawing on the glass transition temperature T_g of amorphous polycarbonate was carried out. The T_g attains a maximum at a draw ratio in the range from 1.6 to 2.0. The relationship between the change of structure and T_g is discussed in terms of the configurational entropy and the rate of molecular motion in local mode relaxation. The variation of T_g with drawing may be explained by using the iso-entropy theory. The frequency of the maximum in the dielectric loss f_max and the dielectric relaxation strength Δε of the β mechanism changed with drawing in the same way as that of T_g. Based on the parallel behavior in these results, it is reasonable to consider that the β process of local mode relaxation of polyesters such as PC and PET reflects the structure of the glassy state.     

First isolation and characterization of 1,2-oxaphosphetanes with three phenyl groups at the phosphorus atom in typical Wittig reaction using cyclopropylidenetriphenylphosphorane

1,2-Oxaphosphetanes bearing three phenyl groups directly bound to the phosphorus atom were successfully isolated for the first time as stable crystals in the typical Wittig reaction of cyclopropylidenetriphenylphosphorane with activated carbonyl compounds. X-ray analysis of the oxaphosphetane showed that the phosphorus atom is at the center of a slightly distorted trigonal bipyramidal structure. Thermal decomposition of these oxaphosphetanes was carried out to give the starting carbonyl compounds and Wittig reaction products, olefins.     

A new flow-type cell by the application of magnetic microfluidic chip

Using a magnetically formed channel called a magnetic channel, a new flow-type cell is proposed. The magnetic channel consists of magnetic walls that are formed by heterogeneous distributions of magnetic flux density around a ferromagnetic track under a magnetic field. The magnetic wall separates the paramagnetic oxidant solution from the diamagnetic reductant solution at a liquid–liquid interface without any solid membranes. In the magnetic channel formed on the cathode, the oxidant solution flows in a quasi-frictionless mode. The anode is placed in the reductant solution surrounding the magnetic channel. Such a geometrical configuration between the oxidant and reductant solutions is interchangeable depending on the magnetism of the solutions. To examine this concept, a Daniel cell system was adopted, where the copper ion in copper sulfate solution is employed as the oxidant and the zinc atom of zinc electrode as the reductant. The copper ion is paramagnetic, so that 1 mol dm⁻³ copper sulfate solution is injected into the magnetic channel formed on the copper cathode. Zinc sulfate solution (1 mol dm⁻³; diamagnetic) together with the zinc anode are placed surrounding the magnetic channel. The performance of this flow-type battery was examined up to a current density of 22 mA cm⁻². This paper was presented at the International Symposium on Magneto-Science 2005, Yokohama, 2005. Contribution to the special issue “Magnetic Field Effects in Electrochemistry.”     

Efficient convergent synthesis of 1alpha,25-dihydroxyvitamin D3 and its analogues by Suzuki-Miyaura coupling

[reaction: see text] 1alpha,25-Dihydroxyvitamin D(3) was synthesized by the Suzuki-Miyaura coupling of the A-ring intermediate 1, which was efficiently prepared from readily available 1,7-enyne 2, with the corresponding boronate compound of the C,D-ring portion. The method was applied to prepare des-C,D analogues of 1alpha,25-dihydroxyvitamin D(3).     

Site selectivity switch in Lewis acid catalysis. Mechanism and kinetic simulation of skeletal rearrangement of cyclobutene-fused homoquinones

[reactions: see text] We investigated the site selectivity switch in BF3-catalyzed dual skeletal rearrangements of cyclobutene-fused diarylhomobenzoquinones by changing the stoichiometric amount of acid concentration. From the lower to the higher equivalency of BF3 x Et2O, the branching product ratios (path A/path B) obeyed nonlinear sigmoid curves against the equivalency of BF3 x Et2O. The observed selectivity profiles were simulated to elucidate factors that govern thermodynamic aspects (binding affinity K of each carbonyl function with acid) and kinetic aspects (rate constants k for the cyclobutene-ring cleavage).     

Trypsin-catalyzed synthesis of dipeptide containing alpha-aminoisobutyric acid using p- and m-(amidinomethyl)phenyl esters as acyl donor

Two series of inverse substrates, p- and m-(amidinomethyl)phenyl esters derived from N-(tert-butyloxycarbonyl)amino acid, were prepared as acyl donor components for enzymatic peptide synthesis. They were found to be readily coupled with an acyl acceptor such as L-alanine p-nitroanilide to produce dipeptide. An alpha-aminoisobutyric acid containing dipeptide was especially obtained in satisfactory yield. Streptomyces griseus trypsin was a more efficient catalyst than the bovine trypsin. The optimum condition for the coupling reaction was studied by changing the organic solvent, pH, and acyl acceptor concentration. It was found that the enzymatic hydrolysis of the resulting product was negligible.     

In situ FTIR spectroscopic study on crystallization process of isotactic polystyrene

The melt crystallization process of isotactic polystyrene (i-PS) was studied by means of in situ Fourier transform infrared (FTIR) spectroscopy, with a focus on the conformational changes during the induction period. The spectra obtained during the induction period suggested the occurrence of some ordered structure that is characterized by higher regularity and packing of the helical moieties than observed in the melt. This ordered structure was clearly different from the amorphous structure, and close to the crystal structure. The Avrami analysis indicated that the formation process of the ordered structure at the late stage of the induction period is similar to the growth process of the crystallites after the induction period. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1227–1233, 1998     

Measurement of Local Sodium Ion Levels near Micelle Surfaces with Fluorescent Photoinduced‐Electron‐Transfer Sensors

The Na⁺ concentration near membranes controls our nerve signals aside from several other crucial bioprocesses. Fluorescent photoinduced electron transfer (PET) sensor molecules target Na⁺ ions in nanospaces near micellar membranes with excellent selectivity against H⁺. The Na⁺ concentration near anionic micelles was found to be higher than that in bulk water by factors of up to 160. Sensor molecules that are not held tightly to the micelle surface only detected a Na⁺ amplification factor of 8. These results were strengthened by the employment of control compounds whose PET processes are permanently “on” or “off”.