Facile palladium(0)-catalyzed ring expansion reactions of hydroxy methoxyallenyl cyclic compounds via hydropalladation

Palladium(0)-catalyzed one-atom ring expansion of various hydroxy methoxyallenyl compounds has been achieved in excellent yields without the use of aryl halides. Hydroxy methoxyallenylisoindolinones, -indanones, and -phthalans have been readily converted to the corresponding isoquinolones, naphthoquinones, and isochromanones in the presence of P(o-tolyl)(3).     

Tetracyanoresorcin[4]arene ion channel shows pH dependent conductivity change

A pH sensitive artificial ion channel, tetracyanoresorcin[4]arene, whose pK(a1) to pK(a3) are around pH 7, was synthesized. Conductivities for potassium ion were increased by the progress of dissociation at the channel mouth.     

New ring-expansion reactions of hydroxy propenoyl cyclic compounds under palladium(0)/phosphine-catalyzed conditions

[reaction: see text] Palladium(0)-catalyzed one-atom ring-expansion of 1-hydroxy-2,2-dialkyl-1-propenoylindan derivatives has been achieved in the presence of P(o-tolyl)(3) giving 2-hydroxy-3,3-dialkyl-2-vinyl-1-tetralone derivatives in excellent yields. This ring-expansion reaction was applied to a 17-(1-oxo-2-propenyl)-beta-estradiol derivative and furnished a similar ring-expanded product in an excellent yield.     

Synthesis of N-substituted cyclic triglycines and their response to metal ions

N,N^′,N^″-Trisubstituted-cyclo-triglycines were synthesized. The major conformation of these compounds has C₃ symmetry, and the carbonyl groups and substituents on the nitrogen are inclined in the same direction. Their response to various metal ions was estimated by constructing ion-selective electrodes. Two of them responded selectively to Ca²⁺ over other cations, demonstrating that N,N^′,N^″-trisubstituted-cyclo-triglycines provide a new scaffold to act as host molecules.     

Probingb-quark charged-current chiral structure viaΛ b semileptonic decay

Λ _b semileptonic decay to \(\Lambda _c e\bar v_e \) is studied within the heavy quark effective theory, whereΛ _b is moving and polarized along the direction of its motion. Normalized energy distributions ofe andΛ _c are both calculated forV±A interactions by taking the corrections and electronp _t cut effects into account. It is shown that the form factor (Isgur-Wise function) effects are significant: The shapes of the distribution curves are thereby considerably changed in comparison with those calculated within the quark model. In case of the electron energy spectrums, the difference between theV±A interactions are enhanced, while that in theΛ _c energy spectrums decreases. On the other hand, the corrections are found to be negligible in both spectrums.     

Electrothermal atomic absorption spectrometric determination of copper and zinc in high-purity bismuth after thiocyanate extraction

Copper and zinc (0.01–1 μg g^?1)in high-purity bismuth are extracted together as their thiocyanate complexes into methyl isobutyl ketone and determined by atomic absorption spectrometry with a tungsten-strip atomizer. The concentrations of copper found by the proposed method agree well with the values obtained by similar atomic absorption spectrometric methods involving prior extraction of copper as its bathocuproine or diethyldithiocarbamate complex.     

THE CHLOROPHYLL a AGGREGATE ABSORBING NEAR 685 nm IS SELECTIVELY FORMED IN AQUEOUS TETRAHYDROFURAN*

An aqueous solution of 2–12% (vol/vol) tetrahydrofuran (THF) induced the selective aggregation of chlorophyll a (Chl a) to form a novel species, A-685, absorbing near 685 nm. The formation of A-685 was closely correlated with a decrease in water activity of the solution. A Raman spectrum of the Chl a species formed in the presence of 6% THF suggests a unique interaction among Chl a, solvent THF and water molecules to give a stacked aggregate (Chl a.THF.H₂O.THF.Chl a). The circular dichroic spectrum of the Chl a species formed in the 6% THF aqueous solution showed an intense signal that had negative and positive wings with about 100-fold larger molar ellipticity for the A-685 than for monomer. However, Chl a', the C10 epimer of Chl a, and chlorophyllide, with a phytyl chain replaced by an ethyl group, did not form A-685 in 6% THF. These clearly indicate that 10-methylcarboxylate and the phytyl chain have a significant role in stabilizing A-685. A possible structure for A-685 is proposed as a novel in vitro model for the P-680 Chl a dimer.     

Development of a simple system for dehydrocondensation using solid-phase adsorption of a water-soluble dehydrocondensing reagent (DMT-MM)

It has been indicated that hydrophilic solid powder to which aqueous solution of a novel dehydrocondensing reagent DMT-MM is adsorbed becomes a simple solid-phase dehydrocondensing reagent of low cost. Reaction in a liquid--liquid biphasic system on the surface of a solid phase with a large area was accelerated by suspending this powder in a dichloromethane solution of a carboxylic acid and an amine to be condensed. The reaction was rapid with a high yield despite the heterogeneity of the system. Like general solid-phase reagents, a hydrophobic carboxamide alone could be isolated at a relatively high purity only by filtration of the resulting suspension of reaction mixture.