Recognition of Multiple Methyl Groups on Aromatic Rings by a Polyaromatic Cavity

The methyl group is a small substituent, usually showing relatively weak or no interactions with other functional groups and metal ions. Herein, we present the recognition of the number of methyl groups on synthetic and natural aromatic compounds (i.e., benzene and xanthine derivatives, respectively) by the 1 nm‐sized polyaromatic cavity of a coordination capsule in water. Detailed competitive encapsulation experiments as well as X‐ray crystallographic analysis revealed that multiple guest–host CH₃–polyaromatic interactions in the confined nanospace are key driving forces for the high selectivity.     

Anisotropic Expansion of an M2L4 Coordination Capsule: Host Capability and Frame Rearrangement

Anisotropic expansion of a spherical M₂L₄ coordination capsule through the elongation of the ligand led to a new M₂L′₄ capsule. The expanded capsule provides an elliptical cavity encircled by polyaromatic frameworks with large openings and thereby can encapsulate elliptical fullerene C₇₀ and monofunctionalized fullerene C₆₀ in high yields. In addition, selective formation of a new M₂L₂L′₂ capsule occurs by mixing the original M₂L₄ and expanded M₂L′₄ capsules in a 1:1 ratio upon addition of C₆₀ or monofunctionalized C₆₀ as a template molecule.     

Concise,asymmetric total synthesis of spirotryprostatin A

[structure: see text] The structurally intriguing cell-cycle inhibitor spirotryprostatin A has been synthesized utilizing an azomethine ylide dipolar cycloaddition reaction as the key step. This pentacyclic alkaloid contains a prenylated tryptophan-derived oxindole moiety that has been created in a regiocontrolled and stereocontrolled manner in a single step.     

Chemical Modification of Chitosan, 17

The Michael reaction of chitosan with acrylic acid was carried out successfully, even in water alone as the reaction medium. As a consequence of its good solubility in water, the reaction product, N‐carboxyethylchitosan, showed excellent biodegradable properties with standard activated sludge.

     

Role of added Lewis base and alkylaluminum halide on living cationic polymerization of vinyl ether

In the living cationic polymerization of isobutyl vinyl ether (IBVE) by the CH₃CH (OiBu) OCOCH₃ ( 1 )/EtAlCl₂ initiating system in the presence of the added base in hexane at +40°C, the stability of the initiating system 1 /EtAlCl₂, which form initiating species CH₃CH^⊕ (OiBu) derived from 1 , was investigated. In the presence of the Lewis base such as ethyl acetate or 1,4-dioxane, the active species was stable for 300 min even at +40°C in the absence of IBVE, and the living polymers were quantitatively obtained by adding IBVE. However, the active species was partly consumed by side reactions during the standing time for 60 min in the presence of a less basic additive such as ethyl benzoate, and about 50% of the active species was deactivated in the presence of methyl chloroacetate. Consequently, in the case of a less basic additive such as methyl chloroacetate (which was effective for the fast living polymerization), it can be seen that the careful selection of polymerization conditions was required. The living polymerization rate was dependent on the second order of EtAlCl₂ concentration. EtAlCl₂ induced the cleavage of 1 into CH₃CH^⊕ (OiBu) and EtAl^?Cl₂(OCOCH₃), and the reactivity of CH₃CH^⊕ (OiBu) and propagating carbocation may be controlled by EtAl^?Cl₂(OCOCH₃) with the aid of other EtAlCl₂. Et_1.5AlCl_1.5 exists as a bimetallic complex of EtAlCl₂ and Et₂AlCl, and it is expected that the polymers having a bimodal molecular weight distribution will be obtained due to two kinds of counteranions coming from EtAlCl₂ and Et₂AlCl. However, in the cationic polymerization of IBVE by 1 /Et_1.5AlCl_1.5 in the presence of ethyl acetate, the living polymer exhibiting a unimodal and very narrow molecular weight distribution was obtained. Thereby, it was suggested that the counteranions, EtAl^?Cl₂(OCOCH₃) and Et₂Al^?Cl(OCOCH₃), exchange rapidly with each other. © 1994 John Wiley & Sons, Inc.     

N,N′,N″—三(对—甲苯磺酰基)二亚乙基三胺的合成

二亚乙基三胺与对—甲苯磺酰氯在碳酸钾存在下,发生对甲苯磺酰化反应,生成N,N′,N″-三(对—甲苯磺酰基)二亚乙基三胺,产率96％。考察影响反应的几个因素。     

Preparation of multilayered gold-silica-polystyrene core-shell particles by seeded polymerization

A preparation method for multilayered gold-silica-polystyrene core-shell composite particles is proposed. The gold-silica core-shell particles of 192-nm-sized, synthesized by coating the 18-nm-sized gold particles with silica by a seeded growth technique, were used as cores for succeeding polystyrene coating. After surface modification of gold-silica composite particles by methacryloxypropyltrimethoxysilane (MPTMS), polymerizations of styrene (0.16-0.4 M) were conducted with 8 x 10(-3) M of potassium persulfate initiator in the presence of 1 x 10(-3) M of sodium p-styrenesulfonate anionic monomer. Multilayered core-shell gold-silica-polystyrene particles that contained a single core could be obtained. The coefficient of variation of size distribution (CV) of the composite particles was less than 7%, and polystyrene shell thickness was in a range of 193 to 281 nm.     

Hyperfine interaction of13O and23Mg implanted in Pt

The spin relaxation timeT ₁ for short-lived beta emitters¹³O and²³Mg implanted in Pt have been measured for the first time;T ₁T¹³O) = 2.90 ±0.65 Ks andT ₁ T(²³Mg) = 1665 ±140 Ks. The Knight shift for¹³O in Pt was measured at 300 K to beK(¹³O) = +(4.23 ±0.14) × 10^–3. In the case of¹³O, the Knight shift is unusually large and the relaxation time is unusually fast compared with other interstitial impurities in Pt. A KKR band-structure calculation reproduces the present large Knight shift fairly well.     

An autosampler with a short transfer line for Curie point pyrolysis capillary gas chromatography

A new multichannel autosampler which can automatically analyze up to twenty samples in sequence has been developed for Curie point pyrolysis – capillary GC. Compared with a previous system [1] the transfer line between the pyroysis unit and chromatograph is shorter, and thus has less dead volume, and can be operated at a higher temperature (300 °C). The relative yields of higher boiling point, highly polar, and thermally labile pyrolysates generated from polymers, and the reproducibility, were better than those obtained from the previous autosampler. To facilitate rapid operation an additional flow controller is installed on the new device to shorten the time taken to purge air from the sampler.     

Photoluminescence and FT-IR studies of the dissociative adsorption of H2 on the active ZrO2 catalyst and its role in the hydrogenation of CO

Photoluminescence and FT-IR studies of the adsorption of H₂ on ZrO₂ catalysts have been performdd to clarify the true natuee of active surface sites for the activaiion of H₂ in connection with the CO — H₂ reaction on the catalyst. The results indicate that the coordinatively unsaturated surface sites with different coordination numbers are generated on the surfaces by evacuation at temperatures higher than 600 K. These surface sites of lower coordination play a significant role in the reversible and irreversible dissociative adsorption of H₂ on the active ZrO₂ catalyst. The former seems to act as active hydrogen species for the CO — H₂ reaction to form branched hydrocarbons on the ZrO₂ catalyst.