Alkenyl- and aryl[2-(hydroxymethyl)phenyl]dimethylsilanes: an entry to tetraorganosilicon reagents for the silicon-based cross-coupling reaction

Alkenyl- and aryl[2-(hydroxymethyl)phenyl]dimethylsilanes, highly stable tetraorganosilicon reagents, are found to react with aryl and alkenyl iodides in the presence of a palladium catalyst and K2CO3 as a base, significantly milder conditions compared with those ever reported for the silicon-based cross-coupling reactions. The reaction tolerates a wide range of functional groups, including silyl protectors, and allows a gram-scale synthesis to recover and reuse the silicon residue.     

Thermal decomposition of vinylacetylene in shock waves

The thermal decomposition of vinylacetylene (C₄H₄) was studied behind reflected shock waves using both a single-pulse method (reaction time between 0.8 and 3.3 ms) and a time-resolved UV-absorption method (230 nm). The studies were done over the temperature range of 1170–1690 K at the total pressure range of 1.3–2.3 atm. The mechanism was used to interpret both the early and late stages of vinylacetylene decomposition at the high temperatures. It was confirmed that C₄H₄ dissociation proceeded through the following three channels. The rate constant expression of reaction (1) was determined as k₁ = 6.3 × 10¹³ exp(?87.1 kcal/RT) s^?1. The rate constants of the succeeding reactions (chain reaction, C₄H₄ + H → i-C₄H₃ + H₂ and C₄H₄ + H → C₂H₂ + C₂H₃ and decomposition reactions of free radicals, i-C₄H₃ + M → C₄H₂ + H + M) were confirmed or estimated. © John Wiley & Sons, Inc.     

Hydration structure around a non-electrolyte molecule as revealed by monte carlo calculation: have you seen the “iceberg”?

Monte Carlo calculations have been carried out for pure water and an infinitely dilute aqueous solution of methanol at 298.15 K at ordinary density by the Metropolis method in NTV ensemble. The hydration structure around methanol revealed by a graphic display technique indicates a structure-forming effect near the hydrophobic group.     

Evaluation and application of liquid chromatographic columns coated with 'intelligent' ligands: (I) acylcarnitine column

Unique stationary phases of octadecylsilica (ODS) coated with acylcarnitines have been developed for liquid chromatographic columns. The ODS column coated with acylcarnitine was readily prepared by recycling the solution containing acylcarnitine through an ODS column in a closed loop. Acylcarnitine was adsorbed on the ODS surfaces by hydrophobic interaction between the acyl group of acylcarnitine and the octadecyl group of the ODS phases. The ODS column coated with stearoylcarnitine (CN-18 column) was the most stable among the four columns coated with acylcarnitines of various acyl chain lengths (decanoylcarnitine, lauroylcarnitine, myristoylcarnitine, and stearoylcarnitine) under the condition of delivery of the mobile phase, indicating that adsorption of acylcarnitine on the ODS surfaces depended on the length of acyl chains. The CN-18 column was usable for delivering the mobile phase contained less than 20% (v/v) acetonitrile, retaining almost the same separation efficiency as the intact ODS column. The retention behavior of ionic solutes on the CN-18 column could be explained by both ionic and electrostatic interactions between the solutes and the stationary phase. The CN-18 column enabled efficient separation of inorganic anions, nicotinic acids, amino acids, and nucleotides. The chiral ODS column coated with enantiomer of stearoylcarnitine, L-stearoylcarnitine (L-CN-18 column) could achieve direct enantiomeric separation of DL-tryptophan, alpha-methyl-DL-tryptophan and DL-3-indolelactic acid using 100% water as the mobile phase. The L-CN-18 column could also separate enantiomers of amino acids and alpha-hydroxycarboxylic acids by ligand-exchange chromatographic mode using a mobile phase containing copper(II) ion. The chiral recognition is discussed for enantiomeric separation on the L-CN-18 column.     

Synthesis of porphyrin-introduced silica gels by sol-gel process

Using a hydroxyl group appended free base porphyrin derivative (HP), porphyrin-introduced silica gels were synthesized by a sol-gel process. The HP content in the materials linearly increased with increasing the HP concentration. Meanwhile, free base tetraphenylporphyrin (TPP) with no hydroxyl groups were almost not incorporated into the silica gels. These facts suggested that the interaction between hydroxyl groups of the HP molecules and silica network is considerably strong. The UV-vis characters of HP-introduced materials were almost the same as pure HP molecules. The Beer's plot indicated that the HP molecules in the materials are dispersed.     

Concise and highly stereocontrolled synthesis of 1-deoxygalactonojirimycin and its congeners using dioxanylpiperidene,a promising chiral building block

[reaction: see text] A concise and stereoselective synthesis of the chiral building block, dioxanylpiperidene 4 as a precursor for deoxyazasugars, starting from the Garner aldehyde 5 using catalytic ring-closing metathesis (RCM) for the construction of the piperidine ring is described. The asymmetric synthesis of 1-deoxygalactonojirimycin and its congeners 1-3 was carried out via the use of 4 in a highly stereocontrolled mode.     

Inhibitory effects of tetragalloylglucose on the complex II of mitochondrial respiratory chain of Ascaris muscle

The effects of tetragalloylglucose (1,2,3,6-tetra-O-galloyl-beta-D-glucose) on purified complex II (succinate-ubiquinone oxidoreductase) of the mitochondrial electron transport system of Ascaris muscle were studied. Both succinate-ubiquinone-1 (Q1) oxidoreductase, and succinate dehydrogenase measured with 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) in the presence of phenazine methosulfate (PMS) were inhibited by tetragalloylglucose. The inhibitions of both reductase activities of complex II were of competitive type, and the inhibitor constant (Ki) for Ascaris complex II (148 nM) was lower than that for rat liver complex II (1.5 microM). Thus, Ascaris complex II is much more sensitive to this inhibitor than the mammalian counterpart.     

Four-m calculations on methanol-water solutions

The structural characteristics of methanol in aqueous solutions, on a molecular level, can be elucidated by four types of calculation: molecular orbital, multiparametric optimization of intermolecular potential function, Monte Carlo, and molecular dynamics. As a first step, the potential between water and methanol was determined by ab initio LCAO SCF molecular orbital calculations with the STO—3G basis set and subsequent multiparametric fitting. This and water—water potentials were used for Monte Carlo calculation on an aqueous methanol solution containing a 1:216 mole ratio of methanol to water. Hydration around methanol is briefly discussed.     

Synthesis of 9-arylamino- and (Z)-9-arylimino-9H-pyrrolo[1,2-a]indoles by reactions of 2-(pyrrol-1-yl)benzaldehydes with aryl amines

Heating mixtures of 2-(pyrrol-1-yl)benzaldehydes and aryl amines under argon afforded 9-arylamino-9H-pyrrolo[1,2-a]indoles, via cyclization of the resulting 2-(pyrrol-1-yl)benzaldimine intermediates. Heating in the presence of oxygen afforded (Z)-9-arylimino-9H-pyrrolo[1,2-a]indoles, which were successfully hydrolyzed with hydrochloric acid to give pyrrolo[1,2-a]indol-9-ones.