Vinyl Polymerization by Metal Complexes. XXXIII. Polymerization of Acrylonitrile Initiated by Triazole-Copper(II) Complex in Dimethylsulfoxide Solution

Polymerization of acrylonitrile initiated by triazole-copper(II) complexes was studied in dimethylsulfoxide solution. It was found that the polymerization proceeds by a free radical mechanism; however, the complexes can hardly homopolymerize methyl methacrylate and styrene. Ability of the complexes to initiate polymerization seems to depend on the substituents of triazole, the sort of solvents, and the counterions of copper(n) salts. From the data of visible spectroscopy and the spin trapping, the initiation mechanism was discussed in terms of reduction of copper(II) followed by forming active species.     

Opening and Addition Modes in Propagation During Radical Polymerization of Fumaric and Maleic Derivatives

Abstract

Polymers of bis(trimethylsilyl) fumarate, di-tert-amyl fumarate, and methyl tert-amyl fumarate were prepared by radical polymerization at 60 or 120°C. The polymers were converted into poly(dimethyl fumarate) via thermolysis or hydrolysis and subsequent methylation to determine the tacticity using ¹³C-NMR spectroscopy. The probabilities of meso addition (P _m) were revealed to be 0.66 (60°C) for the bis(trimethylsilyl) ester, 0.60 (60°C) and 0.52 (120°C) for the di-tert-amyl ester, and 0.54 (60 and 120°C) for the methyl tert-amyl ester. From the temperature dependence of the P _m values, the differences in activation enthalpies and entropies for the meso and racemo additions were evaluated. The microstructure of poly(dimethyl fumarate) derived from poly(maleic anhydride) was also examined. The opening and addition modes in propagation of the fumaric and maleic derivatives were discussed based on the results obtained in the present and previous work.     

Mechanistic action of ferric oxide in the hydrosilylation of 1,6-divinyl(perfluorohexane) with trichlorosilane

In the hydrosilylation of 1,6-divinyl(perfluorohexane) (FDV) with trichlorosilane (TCS) in the presence of catalytic chloroplatinic acid (Pt-Cat) under an air atmosphere (0.99 MPa), a runaway reaction accompanied by a severe pressure release occurred when Fe₂O₃ was present as an impurity in the system. In this study, we investigated the mechanism of action of Fe₂O₃ on this hydrosilylation by monitoring the thermal behavior of TCS/FDV/Pt-Cat/Fe₂O₃ mixtures with various compositions, using an accelerating rate calorimeter (ARC). In the case of TSC/FDV/Pt-Cat, a typical hydrosilylation composition in the industrial process, heat release, possibly due to hydrosilylation, began at 90 °C. On the other hand, for TCS/FDV/Pt-Cat/Fe₂O, the heat release due to hydrosilylation was hardly observed, but abrupt heat and pressure releases occurred at higher temperatures (>170 °C). Like TCS/FDV/Pt-Cat/Fe₂O₃, TCS/FDV, which contain neither Pt-Cat nor Fe₂O₃, released heat and pressure at high temperatures (>210 °C), while the heat and pressure release rates were comparatively low. From these results, the runaway reaction may occur when hydrosilylation is prevented, and Fe₂O₃ behaves as a negative catalyst for hydrosilylation. In the FT-IR spectrum of TCS/FDV/Pt-Cat/Fe₂O₃ after heating, an absorption peak at approximately 1,710 cm^?1, which may be attributed to a carbonyl group, was observed. Thus, it is considered that the runaway reaction observed during the hydrosilylation results from the action of Fe₂O₃ as a negative catalyst for hydrosilylation as well as as an oxidation catalyst for the by-product generated from the reaction between TCS and FDV.     

Thermal behavior and dismantlability of adhesives containing various inorganic salts

As a fundamental study on the development of dismantlable adhesives containing chemically reactive materials, the thermal behavior and dismantlability of an epoxy adhesive containing one of the twenty-seven inorganic salts (chlorides, perchlorates, and nitrates) were observed. In the thermal behavior measured by the differential scanning calorimetry, epoxy adhesives with inorganic salts containing iron, copper, zinc, and aluminum cations released heats of reaction at lower temperatures than the adhesive alone or the adhesives with other inorganic salts. Since such inorganic salts were considered to be effective candidates as fillers in dismantlable adhesives, the adhesion strengths of their mixtures with the adhesive were observed after heat aging at 270 °C for 30 min. The results showed that both chloride and perchlorate salts specifically decreased the adhesion strength after heating. On the other hand, the effect of nitrate salts on the decrease in adhesion strength was low in comparison with the chloride and perchlorate salts.     

Application of Novel Glycosides Prepared with Odorless Benzenethiols in Glycosylation Reaction

p‐Dodecylbenzenethiol (1) and p‐octyloxybenzenethiol (2) were synthesized as new odorless benzenethiols. Moreover, preparation of novel 1‐thioglycosides using 1 and 2 as well as their application for glycosylation reactions was performed. As a result, it was found that these 1‐thio‐glycosides were excellent glycosyl donors, and especially 2‐thio‐sialoside prepared from 1 and 2 afforded the best result to date in terms of α‐ and β‐selectivity in the sialylation where only the single C‐3 hydroxyl group of acceptor D‐galactopyranoside was free. All procedures from the preparation of thioglycosides to glycosylation reaction were attainable under completely odorless conditions.     

Role of Re Species and Acid Cocatalyst on Ir‐ReOx/SiO2 in the C–O Hydrogenolysis of Biomass‐Derived Substrates

The catalytic performance of ReO_x‐modified Ir metal catalyst in the hydrogenolysis of C–O bonds is strongly dependent on the choice of solvent. The acidic property of the Re species becomes obvious in the alkane solvent, and the hydrogenolysis reaction proceeds mainly by acid‐catalyzed dehydration and the subsequent metal‐catalyzed hydrogenation. The acidic property of the Re species is weakened in water; however, the hydrogenolysis reaction proceeds in water via a direct mechanism involving S_N2‐like attack of a hydride species at the interface between Ir and ReO_x on the adsorbed Re alkoxide species. This mechanism enabled the selective dissociation of the C–O bond neighboring the CH₂OH group.     

Controlled Dynamic Helicity of a Folded Macrocycle Based on a Bisterephthalamide with a Twofold Z‐Shaped Structure

Dynamic helicity in a folded macrocycle and control of the helical preference are described. We designed macrocycle 1 with a dual mode of folding through the integration of two flexible units that are arranged twice to form a cyclic structure. As a folding unit, we used a terephthalamide skeleton and a Z‐shaped hydrocarbon: the former acted as a control unit to induce a preference of a particular sense of dynamic helicity and the latter was just a spacer. A terephthalamide unit provided a binding site for capturing a ditopic hydrogen‐bonding guest when it adopted helically folded syn forms (M/P). Thus, only the terephthalamide unit controlled the helical sense of dynamic helicity in a folded macrocycle through the supramolecular transmission of chirality upon complexation with a chiral ditopic guest. In addition, chirality on a host could also contribute to the control of the helical preference in a folded macrocycle, which led to exceptionally enhanced chiroptical signals.     

Development of variable‐magnification X‐ray Bragg optics

A novel X‐ray Bragg optics is proposed for variable‐magnification of an X‐ray beam. This X‐ray Bragg optics is composed of two magnifiers in a crossed arrangement, and the magnification factor, M, is controlled through the azimuth angle of each magnifier. The basic properties of the X‐ray optics such as the magnification factor, image transformation matrix and intrinsic acceptance angle are described based on the dynamical theory of X‐ray diffraction. The feasibility of the variable‐magnification X‐ray Bragg optics was verified at the vertical‐wiggler beamline BL‐14B of the Photon Factory. For X‐ray Bragg magnifiers, Si(220) crystals with an asymmetric angle of 14° were used. The magnification factor was calculated to be tunable between 0.1 and 10.0 at a wavelength of 0.112 nm. At various magnification factors (M≥ 1.0), X‐ray images of a nylon mesh were observed with an air‐cooled X‐ray CCD camera. Image deformation caused by the optics could be corrected by using a 2 × 2 transformation matrix and bilinear interpolation method. Not only absorption‐contrast but also edge‐contrast due to Fresnel diffraction was observed in the magnified images.     

Enantioselective Total Synthesis of Dysidavarone A,a Novel Sesquiterpenoid Quinone from the Marine Sponge Dysidea avara

Dysidavarone A, a structurally unprecedented sesquiterpenoid quinone, was synthesized in 30 % overall yield in a longest liner sequence of 13 steps from commercially available o‐vanillin. A highly strained and bridged eight‐membered carbocyclic core was established by the C7?C21 carbon bond formation through a copper enolate mediated Michael addition to the internal quinone ring.