Synthesis of 2-acylindole-3-acetic acids: a novel base-mediated indole synthesis

An efficient and expedient synthetic route to 2-acylindole-3-acetic acids is described. This work first demonstrates a one-pot room-temperature indole ring construction via the in situ generation of indoline intermediate.     

A New Interpretation of Apparent Induction Period in Ring‐Opening Polymerization of Octamethylcyclotetrasiloxane in Acid Emulsion

A following new interpretation of apparent induction period is proposed considering the experimental results obtained: octamethylcyclotetrasiloxane (D4) is activated by the reaction with acid to generate an activated derivative (A4). A4 reacts with D4 to generate A8, an active species containing eight dimethylsiloxane units. A8 backbites to generate mostly A4 and D4, which causes retardation in polymerization, but occasionally to form A3 and D5. A3 is highly reactive, and when the concentration of A3 exceeds a certain limit, much Ai where i is large enough is formed and promotes fast growth of chain at the interfacial area due to high concentration of D4. The interpretation assumes that A3 accelerates growth of chain faster than other species, and that A8 tends to backbite rather than grow. The interpretation is supported by the experimental results of polymerization conducted with D4 and D3, or D5 and D3 charged.     

Regioselectivity in the 1,3-dipolar cycloaddition reaction of unsymmetric pyridinium dicyanomethylides with dimethyl acetylenedicarboxylate and methyl propiolate: An example of dipole-dipole control of regioselectivity?

A study of the cycloaddition behavior of a series of unsymmetric pyridinium dicyanomethylides with dimethyl acetylenedicarboxylate and methyl propiolate has been carried out. The 1,3-dipolar cycloaddition proceeds in good yield with high regioselectivity to produce the corresponding indolizines and 1:1 adducts. The reactions of isoquinolinium dicyanomethylide follow frontier orbital predictions. In contrast, polar 3-substituted pyridinium dicyanomethylides gave predominantly the corresponding 8-isomers regardless of the substituents. The results can be explained by dipole-dipole interactions.     

Sequential fluorometric quantification of γ-aminobutyrate and l-glutamate using a single line flow-injection system with immobilized-enzyme reactors

A single line flow-injection system with immobilized-enzyme reactors is proposed for the sequential quantification of γ-aminobutyrate (GABA) and l-glutamate. A co-immobilized l-glutamate oxidase and catalase reactor and an immobilized GABase reactor were introduced into the flow line in series. Sample and reagent were injected into the flow line using an open sandwich method. GABA was selectively detected by GABase when α-ketoglutarate at a high concentration and NADP⁺ were injected as the reagents with a sample. When GABA at a high concentration and NADP⁺ were injected as the reagents with a sample, l-glutamate only was determined by the series of enzymatic reactions. NADPH produced by the immobilized-enzyme reactors was monitored fluorometrically at 455 nm (excitation at 340 nm). Linear relationships between the responses and concentrations of GABA or l-glutamate were observed in the ranges of 5.0 × 10⁻⁶-5.0 × 10⁻⁴ M and 1.0 × 10⁻⁵-5.0 × 10⁻⁴ M, respectively. The relative standard deviations for ten successive injections were less than 2% at the 0.5 mM level. This analytical method was applied to the sequential quantification of GABA and l-glutamate that were produced and consumed, respectively, by lactic acid bacteria, and the results showed good agreement with those obtained using liquid chromatography.     

Structural and Magnetic Studies on Nickel(II) and Cobalt(II) Complexes with Polychlorinated Diphenyl(4-pyridyl)methyl Radical Ligands

New magnetic metal complexes with organic radical ligands, [M(hfac)₂(PyBTM)₂] (M = Ni^II, Co^II; hfac = hexafluoroacetylacetonato, PyBTM = (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical), were prepared and their crystal structures, magnetic properties, and electronic structures were investigated. Metal ions in [M(hfac)₂(PyBTM)₂] constructed distorted octahedral coordination geometry, where the two PyBTM molecules ligated in the trans configuration. Magnetic investigation using a SQUID magnetometer revealed that χT increased with decreasing temperature from 300 K in the two complexes, indicating an efficient intramolecular ferromagnetic exchange interaction taking place between the spins on PyBTM and M with J/k_B of 21.8 K and 11.8 K for [Ni^II(hfac)₂(PyBTM)₂] and [Co^II(hfac)₂(PyBTM)₂]. The intramolecular ferromagnetic couplings in the two complexes could be explained by density functional theory calculations, and would be attributed to a nearly orthogonal relationship between the spin orbitals on PyBTM and the metal ions. These results demonstrate that pyridyl-containing triarylmethyl radicals are key building blocks for magnetic molecular materials with controllable/predictable magnetic interactions.     

3,14‐Bis(p‐nitrophenyl)‐17,17‐dipentyltetrabenzo[a,c,g,i]‐fluorene: A New Fluorophore Displaying Both Remarkable Solvatochromism and Crystalline‐Induced Emission

A series of 17,17‐dialkyl‐3,14‐diaryltetrabenzofluorenes were efficiently prepared by using Suzuki–Miyaura cross‐coupling reactions of the corresponding 3,14‐dibromo derivatives. Studies of the unique fluorescence properties of these compounds showed that they display intense blue to yellow fluorescence with high quantum yields in the solution state and blue to orange fluorescence with moderate quantum yields in the solid state. In addition, the fluorescence wavelength of the bis(p‐nitrophenyl) derivative is remarkably solvent‐dependent in a manner that correlates with the solvent polarity parameter E_T(30). The results of density function theory calculations suggest that the intramolecular charge‐transfer character of the HOMO–LUMO transition is responsible for the large solvent effect. Moreover, addition of water to a tetrahydrofuran (THF) solution of this compound leads to quenching of the yellow fluorescence owing to an increase in the solvent polarity. However, when the amount of water fraction exceeds 70 %, a new fluorescence band appears at the same orange‐red emission wavelength as that of the solid‐state fluorescence. This observation suggests the occurrence of a crystallization‐induced emission (CIE) phenomenon in highly aqueous THF.     

A study to control chemical reactions using Si:2p core ionization: site-specific fragmentation

In an aim to create a "sharp" molecular knife, we have studied site-specific fragmentation caused by Si:2p core photoionization of bridged trihalosilyltrimethylsilyl molecules in the vapor phase. Highly site-specific bond dissociation has been found to occur around the core-ionized Si site in some of the molecules studied. The site specificity in fragmentation and the 2p binding energy difference between the two Si sites depend in similar ways on the intersite bridge and the electronegativities of the included halogen atoms. The present experimental and computational results show that for efficient "cutting" the following conditions for the two atomic sites to be separated by the knife should be satisfied. First, the sites should be located far from each other and connected by a chain of saturated bonds so that intersite electron migration can be reduced. Second, the chemical environments of the atomic sites should be as different as possible.     

Selectivity in Consecutive SNAr-Dequaternization Reactions of Chlorodiazines with Tertiary Amines

Consecutive S_NAr-dealkylation reactions of chlorodiazines such as 2-chloropyrimidine and 3, 6-dichloropyridazine with tertiary amines took place in a highly selective fashion.     

Asymmetry in the Main Chain of Poly-9-O-methacryloylquinine

Anionic and radical polymerizations of 9-O-methacryloyl-quinine were performed by using n-butyllithium and azo-bisisobutyronitrile as initiators. Temperature and solvent effects on optical rotation of the polymers were studied. Based on these effects and ORD and CD spectra of polymers, it was concluded that the polymer, which was prepared by n-butyllithium in toluene, has asymmetric conformation in the main chain.     

The First Synthesis of N-Alkyl-N-Arylthiocarbamoylacetates and Acetic Acids

N-Alkyl-N-arylthiocarbamoylacetates, the key intermediates for the synthesis of novel antinephritic agents, have been prepared for the first time. Some of the esters were in turn hydrolyzed to the corresponding acids. An alternative, indirect synthetic route was also developed to prepare some unusual acids.