Simplified bicyclic cage-type molecule as a C 3 -symmetric host: X-ray and FTIR characterization of encapsulation of a nitrile molecule

We synthesized a new amine-type host molecule 2 by 2 steps, using 1,3,5-tris(aminomethyl)-2,4,6-trimethylbenzene and 2,6-pyridinedicarboxaldehyde as starting materials. Recrystallization of 2·6H₂O from hot acetonitrile, hot propionitrile and hexane/benzonitrile solutions gave colorless crystals of MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN. In the former two crystals, the nitrile compounds were captured inside of the cavity of 2. On the other hand, in the latter one, the benzonitrile was laid outside 2. Infrared spectral measurements of MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN showed that absorption bands assignable to the C ≡ N stretching vibrations of nitrile compounds were observed at 2240, 2241, and 2226 cm^?1 for MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN, respectively. The former two peaks shifted to a lower energy region by 6–13 and 21–26 cm^?1 than those of liquid and gas phases of MeCN and EtCN, respectively. That for 8H₂O@2·PhCN shifted to a slightly lower region by 2 and 12 cm^?1 those of liquid and gas states of PhCN, respectively, indicating that the outer benzonitrile molecule dose not so much interact with 2 in the crystal.     

Photodimerization and photooxygenation of 9-vinylcarbazole catalyzed by titanium dioxide and magnesium perchlorate

<正>Photoreaction of 9-vinylcarbazole in acetonitrile in the presence of titanium dioxide and a catalytic amount of magnesium perchlorate gave 3,6-di(9-carbazolyl)-1,2-dioxane as a photooxygenated product via photodimerization of 9-vinylcarbazole.The photoreaction proceeds via an electron transfer mechanism,where magnesium perchlorate accelerated formation of the photo-oxygenated product.     

Sequence-Controlled Catalytic One-Pot Synthesis of Siloxane Oligomers

Silicones are highly valuable poly- and oligomeric materials with a broad range of applications due to their outstanding physicochemical properties. The core framework of silicone materials consists of siloxane (Si−O−Si) bonds, and thus, the development of efficient siloxane-bond-forming reactions has attracted much attention. However, these reactions, especially “catalytic” siloxane-bond-forming reactions that enable the selective formation of unsymmetrical siloxane bonds, remain relatively underdeveloped. On the other hand, controlled iteration has become a powerful tool for the sequence-controlled synthesis of poly- and oligomeric compounds. Recently, control over the siloxane sequence has been achieved by the one-pot iteration of a B(C₆F₅)₃-catalyzed dehydrocarbonative cross-coupling of alkoxysilanes with hydrosilanes and a B(C₆F₅)₃-catalyzed hydrosilylation of carbonyl compounds. Thus, it is now possible to generate linear, branched, and cyclic sequence-specific oligosiloxanes in a highly selective manner under chloride-free conditions.     

Development and flow evaluation of electro-rheological nano-suspensions

An attempt has been made to develop a candidate for electro-rheological (ER) nano-suspensions based on anatase titanium dioxide with a particle diameter around 300 nm. The micro-gap flow behavior and microstructure were evaluated for a suspension with a particle volume fraction of 8.8 vol.%. The ER effect was investigated for the nano-suspension. The effect of shearing time on the ER responses was also investigated. The ER effect was discussed in comparison to the effect previously reported for the nano-suspension based on rutile titanium dioxide with a particle diameter around 15 nm.     

Rhodium‐Catalyzed Synthesis of Chiral Spiro‐9‐silabifluorenes by Dehydrogenative Silylation: Mechanistic Insights into the Construction of Tetraorganosilicon Stereocenters

Mechanistic insight into the construction of quaternary silicon chiral centers by rhodium‐catalyzed synthesis of spiro‐9‐silabifluorenes through dehydrogenative silylation is reported. The C₂‐symmetric bisphosphine ligand, BINAP, was effective in controlling enantioselectivity, and axially chiral spiro‐9‐silabifluorenes were obtained in excellent yields with high enantiomeric excess. Monitoring of the reaction revealed the presence of a monohydrosilane intermediate as a mixture of two constitutional isomers. The reaction proceeded through two consecutive dehydrogenative silylations, and the absolute configuration was determined in the first silylative cyclization. Competitive reactions with electron‐rich and electron‐deficient dihydrosilanes indicated that the rate of silylative cyclization increased with decreasing electron density on the silicon atom of the starting dihydrosilane. Further investigation disclosed a rare interconversion between the two constitutional isomers of the monohydrosilane intermediate with retention of the absolute configuration.     

Effects of Tube Materials on Capillary Chromatography Based on Tube Radial Distribution of Ternary Mixture Carrier Solvents under Laminar Flow Conditions

A capillary chromatography system was developed using an open capillary tube and a ternary solvents carrier solution of water-hydrophilic/hydrophobic organic solvent mixture. The chromatography is called a tube radial distribution chromatography (TRDC) system. The TRDC system works without applying high voltages or using specific columns, such as monolithic and packed columns. In this study, the effects of tube materials on separation performance were examined in the TRDC system, by using poly(tetrafluoroethylene) (PTFE; 100–400?μm inner diameter), polyethylene (PE; 200?μm inner diameter), and copolymer of (tetrafluoroethylene–perfluoroalcoxyethylene) (PTFE–PFAE; 100?μm inner diameter) capillary tubes. An analyte solution of 2,6-naphthalenedisulfonic acid and 1-naphthol as a model was subjected to the system with a water–acetonitrile–ethyl acetate carrier solution; 15:3:2 volume ratio (water-rich carrier) and 3:8:4 volume ratio (organic solvent-rich carrier). The flow rates were adjusted to be 0.5?μL?min^?1 for PTFE and PTFE–PFAE tubes as well as 2.0?μL?min^?1 for PE tube under laminar flow conditions. These analytes in the solution were separated in this order with the water-rich carrier solution with baseline separation in the three capillary tubes, while they were eluted in the reverse order or not separated with the organic solvent-rich carrier solution. The effects of tube temperature on separation were also examined with the water-rich carrier solution; the best resolutions were observed at 0?°C of the tube temperature. The obtained results were compared with those of fused-silica capillary tube and discussed.     

Chemical modification of chain end in nylon 4 and improvement of its thermal stability

Two kinds of nylon 4 having an acyllactam group at one or both chain ends were synthesized by the anionic ring‐opening polymerization of 2‐pyrrolidone using N‐benzoyl‐2‐pyrrolidone (BP) or N,N′‐isophthaloylbis‐2‐pyrrolidone (IPP) and potassium tert‐butoxide as an initiator and a catalyst, respectively, and carefully isolated with the suppression of moisture adsorption. The acyllactam at one chain end in the low molecular weight of nylon 4 was quantitatively converted to other functional groups such as carboxy, amine and so on, which were confirmed by matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI TOF) mass spectroscopy. Terminal acyllactam groups telechelating in the nylon 4 at both chain ends were also modified to carboxy and amino groups. From the thermogravimetric analysis (TGA), thermal decomposition point of the modified nylon 4 was increased in comparison with that of the original acyllactam‐type nylon 4, although the acyllactam chain end caused the backbiting depolymerization accompanied with the generation of 2‐pyrrolidone monomer. The direct heating of the acyllactam‐telechelic low molecular weight of nylon 4 mixed with the diamine in bulk also led to improve its thermal stability significantly by the chain extension through the polyaddition reaction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011