Synthesis of well‐defined block copolymer composed of flexible amphiphilic poly(ethylene glycol) and hydrophobic liquid crystalline segments by living coordination polymerization of allene derivatives and its application to thin film with perpendicularly oriented cylindrical nanostructure

A block copolymer composed of a flexible polar poly(ethylene glycol) (PEG) and a less polar liquid crystalline poly(allene) segments is prepared by the living coordination polymerization of an allene derivative possessing trans‐azobenzene‐containing mesogenic substituent by the use of a π‐allylnickel macroinitiator bearing PEG segment. The thin film of the block copolymer is prepared by the spin coating of its solution onto mica or silicon wafer which proves to possess perpendicularly oriented nanocylindrical microphase separated structures as supported by the differential calorimetric, polarized optical microscopic, grazing‐incidence small‐angle X‐ray scattering, transmission electron microscope, and atomic force microscope measurements.     

Sonochemical coating of magnetite nanoparticles with silica

Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating.     

Carbon-Carbon Bond Formation Using Alkenylsulfides

Highly stereoselective C-C bond forming reactions were developed on the basis of nucleophilic addition of alkenylsulfides to aldehydes, imines, and α,β-unsaturated carbonyl compounds.     

Synthesis and Properties of Phosphorus-Containing Aromatic Polyethers

The phosphorus-containing aromatic polyethers were prepared from bis(p-chlorophenyl)phenylphosphine oxide (BCPO) with the sodium salt of several bisphenols by high temperature solution polycondensation. The best result (yield 84%, n _sp /c = 0.15) was obtained from BCPO with bisphenol A (BPA) in dimethyl sulfoxide. However, the polymerization in the solvents such as N, N′-dimethyl-2-pyrrolidone, hexamethylphosphoramide, and N,N′-dimethylformamide, and the polymerization with the other bisphenols HO-C₆H₄-X-C₆H₄?OH, where X = CO, S0₂, CH₃P(O), C₆H₅P(O) in place of BPA gave gumlike polymers. The polymer prepared from BCPO and BPA did not decompose up to ca. 300°C under air or nitrogen atmosphere, but it decomposed slowly at 300–520°C, and decomposed rapidly at 520–540°C. The activation energy (δE) for the maximum rate of weight loss was 47.8 kcal/mole.     

Recent Developments in Asymmetric Phase‐Transfer Reactions

Phase‐transfer catalysis has been recognized as a powerful method for establishing practical protocols for organic synthesis, because it offers several advantages, such as operational simplicity, mild reaction conditions, suitability for large‐scale synthesis, and the environmentally benign nature of the reaction system. Since the pioneering studies on highly enantioselective alkylations promoted by chiral phase‐transfer catalysts, this research field has served as an attractive area for the pursuit of “green” sustainable chemistry. A wide variety of asymmetric transformations catalyzed by chiral onium salts and crown ethers have been developed for the synthesis of valuable organic compounds in the past several decades, especially in recent years.     

Electronic and Steric Effects of Lewis Acidic Organoaluminum Reagents in the Diels-Alder Reaction

The influence of electronic and steric effects of modified organoaluminum reagents to the stereoselectivity in the Diels-Alder and hetero-Diels-Alder reactions has been examined.     

Stereoselective synthesis of the right-hand segment of tubiferal A

Tubiferal A, a triterpenoid isolated from myxomycete Tubifera dimorphotheca, exhibits a reversal effect of vincristine (VCR) resistance against VCR-resistant KB cell lines. The compound possesses a complex structure involving the 6-7-6-5 polycyclic carbon framework with various functional groups. The stereoselective synthesis of the right-hand segment of tubiferal A was achieved on the basis of the cyclopentene annulation method and the semi-pinacol rearrangement reaction of an epoxy alcohol for constructing the trans-fused 6-5 bicyclic skeleton possessing two quaternary carbon atoms at the angular positions.     

Asymmetric phase-transfer reactions under base-free neutral conditions

Although quaternary onium salt-catalyzed phase-transfer reactions are generally believed to require base additives, we discovered even without any base additives conjugate additions of 3-substituted oxindoles proceeded smoothly in the presence of lipophilic quaternary onium bromide under water-organic biphasic conditions. The mechanism of this novel base-free neutral phase-transfer reaction system was investigated, and the assumed catalytic cycle was presented together with interesting effects of water and lipophilicity of the phase-transfer catalyst. The base-free neutral phase-transfer reaction system could be applied to highly enantioselective conjugate additions, aldol reaction, sulfenylation, and chlorination under the influence of chiral bifunctional onium bromides as key catalysts.