Highly selective catalytic Friedel-Crafts acylation and sulfonylation of activated aromatic compounds using indium metal

The Friedel-Crafts acylation of activated benzenes with various aromatic and aliphatic acid chlorides was studied in the presence of indium metal. The reaction was accomplished in high isolated yields under solvent or solvent-less conditions. The method is also applicable for preparing diaryl sulfones from aromatic compounds and aryl sulfonyl chlorides.     

Cyclopropanation of betulonic acid and its methyl ester with dichlorocarbene generated under phase transfer catalysis conditions

The addition of dichlorocarbene generated under phase transfer catalysis conditions to the double bond of betulonic acid occurs stereoselectively and is accompanied by transformation of the carboxy group leading to the dichloromethyl ester and chloride of 3-oxo-20,29-(dichloromethano)lupan-28-oic acid. Together these products, the chloride of the starting betulonic acid is formed depending on the reaction conditions. The reaction of dichlorocarbene with methyl betulonate leads to the corresponding cyclopropane adduct in a quantitative yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2574–2578, November, 2005.     

An efficacious method for the halogenation of β-dicarbonyl compounds under mildly acidic conditions

A variety of 1,3-diketones, β-ketoesters and malonates can be chlorinated in high yields using sodium hypochlorite in a 5:2 mixture of acetone/acetic acid at 0 °C for 1 h. Similarly, bromination of these dicarbonyl substrates can be accomplished under the same conditions using sodium hypobromite.     

应用新定义的拓扑指数预测烷氧氯硅烷、单硫醚的气相色谱保留指数

根据分子中成键原子i的结构特征和所处的化学环境，新定义了原子i的价点价δi^Y，以价连接矩阵为基础构建了1个新的结构信息价连接性指数^mY。利用线性回归技术分别建立了22个烷氧氯硅烷、61个单硫醚化合物的^mY与这些物质的气相色谱保留指数RI的定量结构／保留相关关系模型(QSRR)。新模型物理意义明确，计算简便，对不同类型化合物在不同极性固定相上的气相色谱保留指数RI具有良好的稳定性和预测能力，新的结构信息价连接性指数能很好地反映化合物的结构特征。     

Tellurium Chloride Complexes in Nonaqueous Solutions

Tellurium(IV) complexes (R₄N)₂[TeCl₆] (T6), (R₄N)[TeCl₅] (T5), and (R₄N)[TeCl₄OH] (T4), where (R₄N)⁺ is tetrabutyl, tetraoctyl, and trialkyl benzyl ammonium cations, were synthesized. Tellurium distribution between aqueous HCl solutions and trialkyl benzyl ammonium chloride solution in caprylic acid was studied. The ¹²⁵Te NMR spectra of aqueous HCl solutions of tellurium have a single averaged peak, whose chemical shift (CS) depends on the acid concentration. ¹²⁵Te NMR spectroscopy has shown that the T4 complex in nonaqueous solutions is kinetically inert and the ligand exchange with the T6 and T5 complexes is retarded. In contrast, the T5 and T6 complexes, when simultaneously present in nonaqueous solutions, rapidly exchange ligands. ¹²⁵Te NMR, IR, Raman, and UV spectroscopic studies have shown that under standard conditions, the reaction (Bu₄N)[TeCl₅]+Bu₄NCl = (Bu₄N)₂[TeCl₆] G⁰ = -19.1(1 ± 0.3) kJ/mol and H⁰ = -6.5(1 ± 0.2) kJ/mol) takes place in methylene chloride solution. The symmetry groups of the synthesized complexes in the solid state and CSs for tellurium solutions (0.2 gatom/liter Te) in methylene chloride were determined: O_h and –58 ppm for T6; C_4v and +75 ppm for T5; and C_3v and +54 ppm for T4 (CS = 0 for a 0.2 mol/liter TeO₂ solution in 11.4 mol/liter HCl).     

Nucleophilic trifluoromethylation of aryl halides with methyl trifluoroacetate

When associated with an alkaline halide, such as cesium fluoride or cesium chloride, and Cu(I) species, methyl trifluoroacetate (MTFA) constitutes a valuable trifluoromethylating agent for substituting aromatic (or heteroaromatic) iodides and bromides. The reaction can be carried out in DMF at 180 °C or, better, in sulfolane which allows he reaction to proceed at a lower temperature (from 140 °C).     

Structure of solvated metal ions in nitrate and chloride solutions of erbium(III) and yttrium(III) in dimethyl sulfoxide

X-ray diffraction measurements on 1M yttrium(III) and erbium(III) nitrate and chloride solutions in dimethyl sulfoxide (DMSO) have shown that Er(III) and Y(III) solutions of equal compositions are isostructural. The intensity difference functions can then be used to derive the detailed structure of the coordination sphere around the metal ions. The DMSO molecules are coordinated over oxygen with average M-O-S bond angles of about 130°. Two different conformations, corresponding to different relative orientations of the M-O and O-S bonds, seem to be prevalent. In the nitrate solutions an average of about 1.5 nitrate ions are coordinated as bidentate ligands to each metal ion. In the chloride solutions about 1.3 chloride ions belong to the inner-coordination sphere.On leave from the Department of Inorganic Chemistry, Royal Institute of Technology, S-10044 Stockholm, Sweden     

Synthesis of 3,5-dioxoalkanoates, 3,5-dioxopimelates and 2,4-dioxoadipates by acylation of 1,3-bis-silyl enol ethers

3,5-Dioxoalkanoates, 3,5-dioxopimelates and 2,4-dioxoadipates were prepared by acylation of 1,3-bis-silyl enol ethers with carboxylic chlorides, methyl 3-chloro-3-oxopropanoate and ethyl 2-chloro-2-oxoacetate, respectively.     

Preparation and structural determination of methyl 3-C-p-tolylsulfonyl-2-C-p-tolylthio-β-d-glucopyanoside derivatives and their 5a-carba-dl-analogs having non-chair conformation in solutions

Methyl 4,6-O-benzylidene-2,3-dideoxy-3-C-p-tolylsulfonyl-2-C-p-tolylthio-β-d-glucopyranoside and its 5a-carba-dl-analog exit mainly in a non-chair conformation in solutions, but the latter occupies a chair conformation in a solid state.     

N-Silylation of amines and amino acid esters under neutral conditions employing TMS-Cl in the presence of zinc dust

An expedient synthetic approach to N-silylamines has been developed. The protocol, using TMS-Cl/zinc dust instead of BSA, is useful for the conversion of amines or amino acid esters to the corresponding silyl derivatives, followed by acylation with an acyl chloride or Fmoc-amino acid chloride to give the corresponding amide or peptide. This procedure, affording products in good to excellent yields, is also efficient for the coupling of sterically hindered amino acids like α,α-dialkylamino acids and NMe-amino acids. Further, the use of an equimolar quantity of organic base, such as Et₃N/pyridine, is circumvented.