Palladium-catalyzed bissilylation of arynes with cyclic disilanes: synthesis of benzo-annulated disilacarbocycles

Arynes, generated in situ from 2-(trimethylsilyl)aryl triflate and a fluoride ion, were found to insert into a silicon-silicon bond of cyclic disilanes in the presence of a catalytic amount of a palladium-tert-alkyl isocyanide complex to afford diverse benzo-annulated disilacarbocycles straightforwardly in modest to high yields.     

Spectrophotometric determination of silver with 4-(3,5-dibromo-2-pyridylazo)-N,N-diethylaniline in the presence of sodium dodecylsulfate

The bidentate ligands, 4-(3,5-DiBr-PAEA) and 4-(3,5-DiBr-PAESA) react with silver(I) ion to form the Agl2 chelate in the presence of anionic or nonionic surfactant. The molar absorptivity at 600 nm is 80 000 l mol^?1 cm^?1 in 0.1% sodium dodecylsulfate solution. Optimum conditions for the spectrophotometric determination of silver in the range 0.1–1.0 mg l^?1 with 3,5-diBr-PAEA are reported. A flow-injection procedure is also presented.     

Preparation and utilization of poly(methacryloylsilatrane) as a salt‐dissociation enhancer in PEO‐based polymer electrolytes

Polymers containing silatrane units were prepared by the free radical polymerization of methacryloylsilatrane (MPS), and their conductivities were evaluated. We confirmed that MPS can be polymerized without excessive decomposition of the silatrane units by the radical polymerization initiated by azobisisobutyronitrile. The chemical structure of the polymerized MPS (pMPS) was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy. The pMPS formed a homogeneous complex with lithium trifluoromethyl sulfonate (LiOTf), although the obtained pMPS/LiOTf complex did not show conductivity. The negligible conductivity was caused by the high glass transition temperature (T_g) of the pMPS matrix, which exceeded 70°C. The pMPS was subsequently utilized as a salt‐dissociation enhancer for the poly(ethylene oxide)‐based polymer electrolyte. MPS was copolymerized with poly[methacryloyl oligo(ethylene oxide)] (pMEO) by free radical polymerization. When the pMEO incorporated a small amount of MPS units (i.e. lower than 15 mol%), the elevation in T_g was not observed, and the conductivity markedly improved. Among the series of copolymers and when compared with pristine pMEO, the copolymer containing 6.3% of MPS units had the maximum conductivity (3.1 × 10^?4 S cm^?1 at 80°C). The Vogel–Fulcher–Tammann fitting parameters showed that the conductivity was improved by the increase in the number of carrier ions. The enhancement in salt dissociation was presumably due to the homogeneous incorporation of polar MPS units. However, when the MPS unit content exceeded 15 mol%, the conductivity was lowered because of the increase in T_g. Copyright © 2013 John Wiley & Sons, Ltd.     

Three-component coupling using arynes and aminosilanes for ortho-selective double functionalization of aromatic skeletons

Arynes were found to couple with aminosilanes and carbonyl compounds in the presence of benzoic acid to provide 2-aminobenzhydrols. Sulfonylimines could also be applied to the reaction, enabling amino and aminomethyl moieties to be incorporated into contiguous positions of aromatic skeletons. Only a small amount of the three-component coupling product was obtained in the absence of benzoic acid, which confirms its vital role in the present reaction.     

Direct access to anthranilic acid derivatives via CO2 incorporation reaction using arynes

CO2 was found to be directly convertible into anthranilic acid derivatives of great synthetic value through a three-component coupling using arynes and amines. Zwitterions arising from nucleophilic attack of amines to arynes serve as key intermediates in the coupling.     

Kinetic studies on Brook-type isomerization of acylpolysilanes to silenes

First-order rate constants of Brook-type isomerization of acylpolysilanes (Me₃Si)₃SiCOR (R = iso-Pr, tert-Bu, Ad, 2,6-xylyl, and Mes) leading to silenes (Me₃Si)₂SiC(OSiMe₃)R at various temperatures were determined. Their Eyring plots gave kinetic parameters of ΔH^‡ = 26.6-29.4 kcal mol⁻¹ and ΔS^‡ = −11.5 to −14.6 cal mol⁻¹ K⁻¹. The isomerization was accelerated by introducing an electron-donating alkyl substituent on the carbonyl carbon. These results are in accordance with a concerted mechanism involving a four-centered transition state.     

Singlet energy migration along an alternating block copolymer of oligothiophene and oligosilylene in solution

The singlet excited-state properties of the block copolymers of oligothiophene and oligosilylene in solution were investigated with several fast spectroscopic methods. Time-resolved fluorescence measurements at room temperature and in a glassy matrix revealed that the singlet excited states of the block copolymers are deactivated accompanying structural changes of the polymer. It became clear from the transient absorption spectroscopy that the absorption peak of the singlet excited state shifted to the longer wavelength side compared to that of the corresponding oligothiophenes because of the sigma-pi conjugation of the oligothiophene and oligosilylene. The intersystem crossing process generating the triplet excited state was also revealed by the transient absorption spectroscopy. Energy migration along the polymer chain was revealed by the fluorescence anisotropy measurements. The time constant for the energy migration became faster as the size of the oligothiophene in the polymer repeating unit became shorter. From comparison with the F?rster theory, the energy migration process was attributed to an incoherent hopping mechanism.