Organomentallic compounds : LXIII. Synthesis,optical stability,stereo-selective and -specific reactions of chiral triorganotin hydrides

Optically active triorganotin hydrides have been synthesized by asymmetric reduction of the corresponding halides. These optically stable compounds undergo stereoselective conversions into other optically stable compounds such as tetraorganotin compounds (by reaction with diazomethane or with bifluorenylidene) or hexaorganoditin compounds (by reaction in the presence of palladium) or into optically unstable compounds such as methylneophylphenyltin chloride (by reaction with CCl₄). The HD exchange between optically active methylneophylphenyltin hydride (deuteride) and triphenyltin deuteride (hydride) occurs with retention of configuration at the metal atom.     

Synthèse de composés comportant deux hétérocycles oxygénés accoles au noyau benzénique, éthers du résorcinol

We wish to report the preparation of new bisheterocyclic compounds derived from resoreinol. We tried to sue methods during this investigation which would be selective and afford only tricyclic linear compounds. The starting material was resorcinol or the monomethylether of resorcinol. By reaction with chloroacetonitrile, acrylonitrile or ethyl chlorobutanoate, we obtained the intermediate compounds which were then cyclized by reaction with sodium acetate or polyphosphoric acid; either a catalytic reduction or treatment with zinc in presence of hydrochloric acid furnished the heterocyclic base. Another condensation followed by a cyclization and a reduction gave the desired compounds.     

Fluorine-containing triphenylenes. Liquid crystalline properties and surface ordering

The synthesis and liquid crystalline properties of two novel series of triphenylenes with 4 or 5 pentafuoropentyloxy tails and 1 or 2 alkoxy tails of varying length are reported. All compounds form wide-range hexagonal columnar phases. The isotropisation temperatures and the corresponding enthalpy changes for the compounds with 4 or 5 fluorinated tails are higher than for the compounds with 6 alkoxy tails, and also higher than for compounds with 6 fluorinated tails. These results indicate that the best ordering is obtained for compounds with a mix of fluorinated and non-fluorinated tails. With increasing length of the alkyl tails in HAT compounds with 4 or 5 fluoroalkoxy tails, the isotropisation temperatures decrease and the d-spacings as observed by XRD increase. All fluoro-containing compounds have a strong tendency for spontaneous homeotropic alignment on surfaces, both hydrophilic and hydrophobic.     

Studies on the synthesis of heterocyclic compounds. Synthesis of 1,3,2-benzoxathia- and 1,3,2-benzodioxastibole derivatives

The preparation of 1,3,2-benzoxathia- and 1,3,2-benzodioxachlorostiboles (IIa-b) by reaction of antimony trichloride with 2-hydroxythiophenol (Ia) or 1,2-benzodiol (Ib) is described. The halogen was easily removed. Thus a Wurtz-like reaction gave the distibole compounds (IVa-b), which were also produced by organolithium compounds or pyridine. The compounds Va-b were obtained with sodium hydroxide, ethoxide and phenoxide, but spiran derivatives VIIa-b, of antimony, were obtained by treating IIa-b with 2-hydroxythiophenol or 1,2-benzodiol in the presence of triethylamine. The structure of the prepared compounds was determined by spectro-scopic methods.     

Preparation and Properties of Inclusion Compounds of Cyclodextrins with Organotransition Metal Complexes

Inclusion compounds of transition metal complexes of cycloocta-1,5-diene (cod) and norbornadiene (nbd) with cyclodextrins were prepared. Two-to-one (cyclodextrin:guest) inclusion compounds were obtained in high yields by the treatment of β-cyclodextrin (β-CD) with [(L)RhCl]₂ (L = nbd or cod) and 1:1 inclusion compounds were obtained by the reaction of β-CD with (cod)PtX₂ (X = Cl, Br, or I) in high yields, while γ-CD formed 1:1 inclusion compounds with (cod)PtX₂ (X = Br or I). The formation of inclusion compounds is selective. α-CD did not form inclusion compounds with any transition-metal complexes with cycloocta-1,5-diene. Thermogravimetric measurements show that the complexes are stabilized by inclusion in cyclodextrin cavities. The inclusion compounds were characterized by ¹ H-NMR, IR, UV, and circular dichroism spectra.     

Data shaving: a focused screening approach

The number of compounds available for evaluation as part of the drug discovery process continues to increase. These compounds may exist physically or be stored electronically allowing screening by either actual or virtual means. This growing number of compounds has generated an increasing need for effective strategies to direct screening efforts. Initial efforts toward this goal led to the development of methods to select diverse sets of compounds for screening, methods to cluster actives into related groups of compounds, and tools to select compounds similar to actives of interest for further screening. In this work we extend these earlier efforts to exploit information about inactive compounds to help make rational decisions about which sets of compounds to include as part of a continuing screening campaign, or as part of a focused follow-up effort. This method uses the information from inactive compounds to "shave" off or deprioritize compounds similar to inactives from further consideration. This methodology can be used in two ways: first, to provide a rational means of deciding when sufficient compounds containing certain structural features have been tested and second as a tool to enhance similarity searching around known actives. Similarity searching is improved by deprioritizing compounds predicted to be inactive, due to the presence of structural features associated with inactivity.     

Identification of nitriles in petroleum products : Complex formation as a method of isolation

Nitrogen compounds were completely removed from a hydrogenated furnace oil by shaking with a mixture of ferric chloride and zinc chloride. The resulting complexes were separated from the oil and thermally decomposed to liberate the nitrogen compounds. After removal of nitrogen bases with hydrochloric acid and indoles, carbazoles, and phenazines with perchloric acid, the nitrogen compounds remaining in the concentrate were separated by fractional clution from an aluminum oxide column and gas chromatography. The following compounds were identified or their presence was indicated in the resulting fractions by their ultraviolet and/or mass spectra: dicyanobenzene, dicyanocyclohexane, cyanoindene, cyano-2,3-dihydroindene, cyanonaphthalene, dicyanoindene, dicyano-2,3-dihydroindene, dicyanonaphthalene, cyanobiphenyl, dicyanooctahydronaphthalene, and/or several of their alkyl derivatives.     

Zur Herstellung von 1,2,3-Tricarbonylverbindungen aus 1,3-Dicarbonylverbindungen. 27. Mitteilung über Reduktone und Tricarbonylverbindungen [1]

The synthesis of 22 substituted tricarbonyl compounds is reported. They were obtained either by oxidation of β-dicarbonyl compounds with SeO₂ or nitrous oxides or by oxidation of the α-bromo-β-dicarbonyl compounds with DMSO. The procedures using SeO₂ or DMSO are more rapid and give in general better yields than other methods described in the literature.     

Gas chromatographic and mass spectrometric determination of nitroaromatics in water

Several methods for the extraction of nitroaromatic compounds from water were compared. High recoveries were achieved with discontinuous or continuous extraction of water with dichloromethane and by adsorption on Amberlite XAD-2, -4 and -8 resins (1:1:1) and elution with dichloromethane. The recoveries obtained with solid-phase extraction using cyano-, phenyl- or octadecyl-bonded phases varied, depending on the compounds studied, and were often low. Nitroaromatic compounds were determined by gas chromatography using an electron-capture or a chemiluminescence detector (thermal energy analyser) and by mass spectrometry using electron impact and positive- and negative-ion chemical ionization.     

Role of metals and metal-deactivators in polymer degradation

The interaction between metals or metallic compounds and polymers is inevitable in the practical use of polymeric articles, and the stability of the polymers is often modified by these materials. Furthermore, the effect of the metallic compounds on the degradation of the polymers is extremely complicated, and is influenced by various factors.

This contribution deals with the possible role of metals or metallic compounds in the degradation of polymers, and this is followed by some typical examples of degradation by metallic compounds, mostly commercial pigments and transition metal compounds of stearic acid and acetylacetone, in typical commercial polymers. Recent studies of the inhibition of the copper-catalyzed thermo-oxidative degradation of polyolefins by deactivators, both commercial reagents and novel products, are discussed.     

氟烷基三甲基硅化合物的合成和反应研究

羰基化合物的氟烷基化反应是把含氟基团引入有机分子中去的一个重要手段。文献报道的主要是通过氟烷基金属试剂来进行此反应。但氟烷基金属试剂不太稳定,容易分解。这就给它们的应用带来了许多不便。我们发现,氟烷基三甲基硅化合物(1)作为氟烷基阴离子前体,在比较温和的条件下,便可使醛发生氟烷基化反应。首先,参照文献方法,通过氟烷基格氏试剂与三甲基氯硅烷反应,方便地制得了两个新的氟烷基三甲基硅化合物 R_F-SiMe_3(1)。     

有机化合物对电感耦合等离子体质谱(ICP-MS)法测定食品中总砷的影响

目的 研究有机化合物对电感耦合等离子体质谱法（ICP-MS）测定食品中总砷的影响,分析总结一般规律,为食品中总砷的准确测定提供理论依据。方法 研究了甲醇和乙醇等14种有机化合物对ICP-MS测定砷的动能歧视模式（KED）信号值和动态反应模式（DRC）信号值的影响,通过分析各有机化合物的电离能、极性和溶解度等性质,推测其在ICP-MS测定体系中对砷响应信号值增敏或者抑制的可能机理。结果 有机化合物对ICP-MS的KED模式测定砷离子As+的信号值有增敏效应,对DRC模式测定氧化砷离子AsO+信号值的影响小于KED模式测定As+的信号值,而且过程也更为复杂。相反,氮氧化物会减弱As+和AsO+的信号值。锗、铟等内标元素原子与砷原子在等离子体中电离行为和灵敏度的差异,使得内标元素校准砷测定信号的漂移受到干扰。结论 推测有机化合物影响ICP-MS测定砷响应信号值的可能机理是：有机化合物和氮氧化物经电离或裂解之后分别生成碳离子或多原子碳离子和氮氧离子或氮氧基团,碳离子或多原子碳离子会与砷原子发生电荷转移反应,增强As+或AsO+的信号值,同时有机化合物也可能会与As+竞争氧气而降低AsO+的信号值,而具有强电负性的氮氧基团可能会与As+和AsO+发生电荷转移反应而减弱其信号值。有机化合物对砷的ICP-MS响应信号值的影响可能是受到有机化合物电离能、溶解度、极性和分子结构等综合因素的结果。     

诱导效应指数与含硫含氮的低碳直链有机化合物的标准汽化热

本文利用诱导效应指数建立了含硫含氮的低碳直链有机物的标准汽化热的简单估算方法，我们利用此法计算了一些含硫含氮的直链有机物的标准汽化热，４１个可比较值的相对误差均在５％以内。     

Furopyridines. XII . Reaction of 3-bromo, 2-phenylthio and 2-phenylthio-3-bromo derivatives of furo[2,3-b]-, furo[3,2-b]-, furo[2,3-c]- and furo[3,2-c]pyridine with several alkyllithiums

This paper describes reactions of 3-bromo- 1a-d , 2-phenylthio- 5a-d and 2-phenylthio-3-bromofuropyridines 6a-d with n-butyl-, t-butyl- and methyllithium and lithioacetonitrile. Lithiation of compounds 1a-d with n-butyl- or methyllithium gave the parent furopyridines 2a-d and o-ethynylpyridinols 3a-d. Reaction of compounds 5a-d with methyllithium afforded o-(phenylthioethynyl)pyridinols 7a-d , which were also yielded by reaction of compounds 6a-d with t-butyl- or methyllithium. The phenylthio group in compounds 7a-d were substituted with t-butyl group by the reaction with excess t-butyllithium. In contrast, 2-phenylthio group in compounds 5a-d and 6a-d was substituted with cyanomethyl group by reaction with lithioacetonitrile to give compounds 11a-d and 10b, c respectively.     

Stability of halide compounds in melt

We demonstrate the utility of thermal analysis for evaluating the stability of halide compounds in melt. The stability of compounds is strongly influenced by the cation polarizing power (CPP) and weakly influenced by the existence or nonexistence of compounds in the phase diagram and the type of anion. The stability of compounds along the halide liquidus curves decreases considerably with decreasing their concentrations in melt or with rising temperature. Original Russian Text ? V.N. Chikanov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 4, pp. 687–690.     

Absolute structure determination of compounds with axial and planar chirality using the crystalline sponge method

The absolute stereochemistry of compounds with axial and planar chirality is successfully determined by the crystalline sponge method without crystallization or derivatization of the compounds. This method is applied to absolute structure determination in the asymmetric synthesis of unique compounds with axial and planar chirality.     

Reactions of Aromatic Nitro Compounds with Bases

Aromatic nitro compounds can react in many ways with bases. The reaction path followed depends mainly on the degree of nitration (with a sharp jump from mononitro to di- and trinitro compounds) and the base used. Redox reactions or nucleophilic aromatic substitutions predominate with mononitro compounds, whereas Meisenheimer additions together with nucleophilic aromatic substitutions are preferred by dinitro and trinitro compounds; deprotonations are less common. The bromine in nitrobromobenzenes can be replaced by metal at low temperatures. Very weak bases generally give electron donor-acceptor complexes.     

Hetero analogs of sesquifulvalene

Heterosesquifulvalenes containing sulfur or oxygen as hetero atom may be prepared, e.g., by condensation of cyclopentadienes with thiopyrones or pyrones in acetic anhydride. Heterosesquifulvalenes containing nitrogen can be obtained from the oxygen compounds by O,N-exchange. The ground state of all these compounds is determined mainly by the nonpolar resonance formula.     

On the importance of charge alternation

The concept of stabilization of polyanionic and polycationic compounds by charge alternation was introduced to explain the course of polymetalation of hydrocarbons and enolates. This concept is generalized to the positional stabilization of polar compounds containing two or more donor or acceptor groups and reconciled with the different known stabilizations of compounds containing a donor and an acceptor group. Various properties of other classes of compounds such as relative acidities and basicities of heterocyclic compounds, charge distribution in cyanines, mesocyanines,oxonoles and aromatic dianions, as well as the regioselectivity of some reactions seem also to obey the rules based on this concept.