The Mechanism of Contact Elimination,A Contribution to Understanding the Function of Polar Catalysts

The current ideas of organic chemists based on the work of Ingold and his school are applied to heterogeneous catalytic eliminations (mostly from haloalkanes and aliphatic alcohols). It is deduced from the activity of the catalysts, the reactivity of the substrates (reactants), and the primary product distribution that these eliminations proceed by a heterolytic mechanism similar to that involved in the liquid phase. The activity of the catalysts (salts and oxides) increases with increasing charge and decreasing radius of the cations and with increasing basicity of the anions. The reactivity of the substrates behaves in much the same manner as in the liquid phase. In contrast with the liquid-phase reaction, the cis-olefins are frequently favored as primary products. The stereospecificity of the reaction is determined from the relative strengths of the interactions between the catalyst cation and the leaving group X^?, and between the catalyst anion and the leaving proton. Only trans elimination has so far been found in the concerted mechanism.     

磺苄青霉素药物电极的研究

报道了一种磺苄青霉素药物电极，以十六烷基三辛基碘化铵为载体，用邻苯二甲酸二壬酯为增塑剂，运用序贯淘汰水平法对膜组成进行了优化；确定了电极最佳膜组成，讨论了一些因素对电极性能的影响。电极响应快速，选择性、稳定性、重现性均较好。电极检测下限可达１．６６×１０＾－６ｍｏｌ／Ｌ，线性范围为６．０３×１０＾－６～１．０×１０＾－１ｍｏｌ／Ｌ，斜率为２８．０ｍＶ／ｐＣ，回收率为９６．１％～１００．４％。可用…     

The Studies of the Reactions of 2, 4, 6-Triphenylpyrylium Tetrafluoroborate with Amino Acids

The reactions of triphenylpyrylium salt 1 with various amino acids were explored and compared. The reactions with most α-amino acids yielded decarboxylation products 2 viadecarboxylation. The reactions with glutamic acid, lysine and ACC (1-aminocyclopropyl-carboxylic acid) gave triphenylpyridine 8, dimer 9 and acid 5a-ace, respectively. The reactionswith β and γ-amino acids yielded triphenylpyridine by intramolecular elimination.     

Synthesis and conversions of metallocycles. 8. Regioselective β-hydrovinylation of α-olefins with the participation of metallocomplex catalysts

A new method is proposed for the synthesis of 2-vinylalkanes by the reactions of aluminocyclopentanes with allyl halides or ethers in presence of catalytic amounts of nickel or cobalt complexes.For previous communication, see [1].Institute of Chemistry, Bashkir Scientific Center, Ural Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 382–385, February, 1992.     

Formation of novel sulfur-containing C60F16 cycloadducts between tetrathiafulvalene and C60F18; a unique six-electron cycloaddition of a fullerene involving F2 loss

Co-evaporation of solutions of C(60)F(18) and tetrathiafulvalene in toluene produces an unsymmetrical C(60)F(16):tetrathiafulvalene adduct through a unique six-electron cycloaddition involving displacement of two fluorine atoms by a terminal Cdbond;C double bond of the fulvalene. The adduct rearranges into two further adducts, one of which is characterised as a new type of fullerene derivative, a thiiranofullerene, formed by elimination of a thioketene moiety from the tetrathiafulvalene adduct. The initial addition also produces a bisadduct in which the addends comprise one tetrathiafulvalene molecule and one in which carbon disulfide has been eliminated. The latter adduct involves cycloaddition of an unsaturated aromatic dithiolactone moiety.     

Density functional theory study on the reactions of X− with CH3SY (X,Y = F,Cl, Br,I)

Gas‐phase anionic reactions X^? + CH₃SY (X, Y = F, Cl, Br, I) have been investigated at the level of B3LYP/6‐311+G (2df,p). Results show that the potential energy surface (PES) of gas‐phase reactions X^? + CH₃SY (X, Y = Cl, Br, I) has a quadruple‐well structure, indicating an addition–elimination (A–E) pathway. The fluorine behaves differently in many respects from the other halogens and the reactions F^? + CH₃SY (Y = F, Cl, Br, I) correspond to deprotonation instead of substitution. The gas‐phase reactions X^? + CH₃SF (X = Cl, Br, I), however, follow an A–E pathway other than the last two out going steps (COM2 and PR) that proceeds via a deprotonation. The polarizable continuum model (PCM) has been used to evaluate the solvent effects on the energetics of the reactions X^? + CH₃SY (X, Y = Cl, Br, I). The PES is predicted to be unimodal in the solvents of high polarity. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

钯催化反应中的β-氢消除反应

总结了作者小组发展的Pd(II)催化的反应, 在卤离子或含氮配体(吡啶、联吡啶、菲咯啉等)存在下淬灭碳—钯键以再生二价钯物种. 卤离子和含氮配体是完成反应的催化循环和高得率所必需的, 它们的主要作用是抑制β-氢消除反应. 对于Pd(0)催化的反应, 控制β-氢消除也是使偶联反应多样化的一个关键, 已发现有许多配体适用于脂肪族化合物的偶联反应. 最近, 又报道了应用卤离子和菲咯啉衍生物为配体应用于这一目的.     

Phosphorylated methano[60]fullerenes containing nitroxyl radicals: synthesis,structures, and electrochemical behavior

Phosphorylated methano[60]fullerenes containing one or two nitroxyl radicals were synthesized for the first time. Their structures were established from spectroscopic data and their compositions, by MALDI-TOF mass spectrometry. Their electrochemical reduction in a system o-dichlorobenzene-DMF/0.1 M Bu₄NBF₄ was studied by cyclic voltammetry, preparative electrolysis, and ESR spectroscopy in combination with in situ electrolysis. Both compounds were found to undergo four-step reduction of the fullerene sphere, reduction of nitroxyl, opening of the three-membered ring, and elimination of addends as carbanions stabilized by protonation and rearrangement into phosphate ions and substituted acetylene, which are accompanied by the formation of free fullerene and dihydrofuranofullerene. The rates of the ring opening and the addend elimination increased with an increase in the negative charge on the fullerene sphere. These reactions are fast in the case of transfer of three electrons. With the use of model compounds, heterogeneous electron transfer to the nitroxyl radical at the potentials of the transfer of the third electron to the fullerene sphere and homogeneous intramolecular electron transfer from the dianion of the fullerene sphere were revealed. The mechanisms of the observed transformations are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1594–1607, July, 2005.     

One-pot synthesis of tetrahydrofuran derivatives via a divalent palladium-catalyzed three-component coupling

Under divalent palladium catalysis, a three-component coupling reaction for synthesizing tetrahydrofuran derivatives has been established. The reaction involves the intramolecular carbopalladation of an alkyne with a carbanion which was generated from the addition of an alkoxide ion to an alkene derivative, followed by allylic chloride insertion to the CPd bond and quenching the CPd bond by β-heteroatom elimination in the presence of excess chloride ions.