Preparation, properties, and X-ray structures of 5,5-bi(8-aminoquinoxalyl)s: novel Wurster-type electron donors with a heterobiaryl skeleton

The title electron donors were prepared by the double condensation reactions of 2,2^′,3,3^′-tetraamino-4,4^′-bis(1-pyrrolidinyl)biphenyl with 1,2-diketones. They adopt twisted conformations in crystal, yet the reversible two-stage one-electron oxidation process suggests the planar geometries for the oxidized species. Depending on the nature of substituents on the pyrazine ring, this π-system can be endowed additional features such as chiroptical properties or metal coordination ability.     

Solid-phase extraction with a dibutylmelamine-imprinted polymer as triazine herbicide-selective sorbent

Triazine herbicide-selective polymer spheres were prepared by molecular imprinting using dibutylmelamine (DBM) as a template in suspension polymerization, and were utilized in solid-phase extraction (SPE) of atrazine. Atrazine-selective SPE was successfully demonstrated with a recovery of ca. 97% and an enrichment factor of 50, proving the good aptitude of DBM as the template species for developing a specific sorbent for triazine herbicides. It is also noteworthy that DBM-imprinted polymers have no possibility of disturbance in agrochemical analyses even if DBM remained in the polymer, which may occur by insufficient washing at the stage of removing the template to yield the binding sites, increasing the availability of imprinted polymers for practical applications.     

Effect of frequency sweep direction on motion of excited ions in fourier transform ion cyclotron resonance cells

Ion motion during frequency sweep excitation was computer simulated to study the effect of the direction of frequency sweep on the z motion of ions in a cylindrical Fourier transform ion cyclotron resonance (FT-ICR) cell. It is shown that the z motion is more forcefully excited by upsweep that by downsweep; thus at large amplitudes ions are more easily ejected to the trapping electrodes by upsweep and larger cyclotron orbits can be achieved by downsweep. This effect was confirmed by experiment and the results are favorably compared with the calculations. From these results it is concluded that downward sweeping is advantageous for ion detection and upward sweeping is preferable for ion ejection. The simulations clearly explain the effect of the direction of frequency sweep by visualizing the directions of the forces that ions experience immediately after the excitation of their cyclotron motion. It was demonstrated by experiment that the z ejection can be reduced by applying a phase-adjusted ac potential to the trapping electrodes.     

Stereoselective generation of Z-ketene S,N-acetal from S-alkyl onium salt of thioamide and its application to diastereoselective α-allylation of thioamide

Highly diastereoselective α-allylation of thioamides has been achieved via S-allylation of thioamide, dehydrohalogenation, and thio-Claisen rearrangement sequences in one pot.     

Palladium-catalyzed intramolecular selenocarbamoylation of alkynes with carbamoselenoates: formation of alpha-alkylidene-beta-lactam framework

Pd-catalyzed intramolecular selenocarbamoylation of alkynes leading to alpha-alkylidene-beta-lactams was developed. This reaction can be applied to thiocarbamoylation and to the synthesis of delta- and epsilon-lactams and a cyclobutanone.     

Novel [4 + 2]-cycloaddition of 1-phenyl-1-benzothiophenium salts with dienes. Experimental evidence for a lack of aromaticity in the thiophene ring

The [4 + 2]-cycloaddition reaction of 1-phenyl-1-benzothiophenium triflates has been conducted for the first time. [4 + 2]-Cycloaddition with dienes such as cyclopentadiene and 1,3-diphenylisobenzofuran occurs successfully to give cycloadducts. This result indicates that the C=C bond of the thiophene ring acts as a 2pi electron component in the cycloaddition reaction. Cycloadducts were formed in high yields with high stereoselectivity. However, the cycloaddition with other less reactive dienes such as 2,3-dimethyl-1,3-butadiene did not take place. The structure and stereochemistry of cycloadduct 2a were analyzed by NMR techniques. Furthermore, reaction of the cycloadducts with sodium methoxide in methanol gave the ring-opened products in high yields.     

Polycyclic N-heterocyclic compounds. XLV. Synthesis of 4-substituted 5,6-dihydrobenzo[h]quinazolines and 6,7-dihydro-5H-benzo[6,7]cyclohepta[1,2-d]pyrimidines and their inhibitory activity on platelet aggregation

The synthesis of 4-substituted 5,6-dihydrobenzo[h]quinazolines and 6,7-dihydro-5H-benzo[6,7]cyclohepta-[1,2-d]pyrimidines with substituents which are an electron-attracting group such as a nitrite, an amide, a thione, or a carboxyl group is described. Their inhibitory activity against collagen-induced platelet aggregation was also investigated.     

Phase relationships and thermodynamic interactions in linear polyethylene–diluent systems

Phase equilibria between linear polyethylene and a number of organic diluents of varying type have been investigated. The diluents include aliphatic alcohols, alkyl phenols, aryl phenols, diphenyl derivatives, alkyl aryl ethers, esters, and ketones. It is found that n-octyl alcohol, n-decyl alcohol, n-lauryl alcohol, p-tert-amyl alcohol, p-octyl phenol, p-nonyl, phenol, diphenyl, diphenylmethane, diphenyl ether, benzyl phenyl ether, and anisole are Θ-solvents for linear polyethylene at temperatures between 120 and 200°C. Thermodynamic interactions are discussed in relation to the type of diluent.