Unexpected, drastic effect of triflic acid on oxidative diacetoxylation of iodoarenes by sodium perborate. A facile and efficient one-pot synthesis of (diacetoxyiodo)arenes

An easy, safe, and effective method for preparing (diacetoxyiodo)arenes from iodoarenes is presented. Addition of trifluoromethanesulfonic acid (triflic acid) as a promoter causes a drastic increase in the yield of (diacetoxyiodo)arenes in the reaction of iodoarenes with sodium perborate. The reaction of the iodoarenes with sodium perborate in acetic acid in the presence of triflic acid at 40-45 degrees C efficiently generates the corresponding (diacetoxyiodo)arenes in high yields within short time.     

Bismuth(III) halides: remarkable doping agents for triflic acid in the catalytic sulfonylation of arenes

The catalytic activity of triflic acid has been dramatically increased by the addition of a catalytic amount of bismuth(III) chloride. Thus, the catalytic sulfonylation of arenes using the new system BiCl₃-triflic acid has been successfully carried out while both components of this catalytic system are poorly active or inactive alone, which suggests a synergy between BiCl₃ and triflic acid. Other bismuth halide-triflic acid systems proved to be active.     

Ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid

The ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid gives the corresponding ketones and alcohols highly efficiently at room temperature. The former catalytic system, RuCl(2)(PPh(3))(3)-t-BuOOH, is preferable to the oxidation of alkylated arenes to give aryl ketones. The latter system, Ru/C-CH(3)CO(3)H, is suitable especially for the synthesis of ketones and alcohols from alkanes. The ruthenium-catalyzed oxidation of cyclohexane with CH(3)CO(3)H in trifluoroacetic acid/CH(2)Cl(2) at room temperature gave cyclohexyl trifluoroacetate and cyclohexanone with 90% conversion and 90% selectivity (85:15). The mechanistic study indicates that these catalytic oxidations of hydrocarbons involve oxo-ruthenium species as key intermediates.     

Synthesis of 2-alkyl- and 2-carboxy-p-tert-butylcalix[4]arenes via the lithiation of tetramethoxy-p-tert-butylcalix[4]arene

[reaction: see text]. Tetramethoxy-p-tert-butylcalix[4]arene reacts readily with n-butyllithium to give a putative monolithiated intermediate that is substituted with alkyl halides and carbon dioxide to give in 60-75% yield conformationally mobile calix[4]arenes monosubstituted at the methylene bridge (2-position). 2-Alkyl- and 2-benzyl-substituted tetramethoxycalix[4]arenes are converted in 62-68% overall yield to the corresponding tetrahydroxy-p-tert-butylcalix[4]arenes by treatment with boron tribromide. The tetrahydroxy-p-tert-butylcalix[4]arenes exist in the cone conformation at room temperature in CDCl3 as judged by NMR spectroscopy.     

Direct, easy, and scalable preparation of (diacetoxyiodo)arenes from arenes using potassium peroxodisulfate as the oxidant

The reaction of arenes with potassium peroxodisulfate, elemental iodine, and acetic acid in the presence of concd sulfuric acid, efficiently generates the corresponding (diacetoxyiodo)arenes in good yields, providing an easy, safe, and effective method for preparing (diacetoxyiodo)arenes from arenes and iodine.     

Synthesis and conformational behaviour of lower-rim tetraacetylated thiacalix[4]arenes

The acylation of thiacalix[4]arenes with AcCl or Ac₂O gave the corresponding lower-rim tetraacetoxy derivatives. In contrast to classical calix[4]arenes, tetraacetylated thiacalix[4]arenes are conformationally mobile in solution and represent a thermodynamic equilibrium of three different conformers at room temperature. As proven by a dynamic ¹H NMR study, conformational preferences of acetylated thiacalix[4]arenes considerably depend on the upper-rim substitution. Hence, t-Bu thiacalixarene prefers 1,3-alternate and 1,2-alternate conformations (43% and 38%, respectively), while the upper-rim unsubstituted compound adopts preferably the partial cone conformation (70%).     

原子荧光光谱法测定铜合金中铋元素含量方法改进

基于原子荧光光谱法测定铋元素时检出限低、测定结果稳定且准确等优点,研究原子荧光光谱法测定铜合金中铋元素含量的方法。在标准系列中加入相近浓度的铜元素标准溶液,原子荧光光谱法测定铜合金中铋元素含量。称取0.1 g样品,加入10 mL硝酸溶解,10%硫脲-5%抗坏血酸溶液7.5 mL预处理样品。在20μg/L的铋标准溶液中加入6 mL浓度为1000μg/mL的铜元素标准溶液。结果表明:在0~20μg/L范围内,该方法线性关系良好,线性方程为I=138.1670c+43.8572,相关系数为0.9996,所测定的样品中铋元素含量的相对误差在-4.3%~7.7%之间,精密度在0.4%~4.7%之间。原子荧光光谱法可作为铜合金中铋元素含量测定的方法。     

Synthesis and Properties of N-(2,2,2-Trichloroethylidene)- and N-(2,2,2-Trichloroethyl)nitrobenzenesulfonamides

Highly reactive N-(2,2,2-trichloroethylidene)nitrobenzenesulfonamides were synthesized by reaction of N,N-dichloronitrobenzenesulfonamides with trichloroethylene. Reactions of N-(2,2,2-trichloroethylidene)nitrobenzenesulfonamides with oxygen and nitrogen nucleophiles gave products of addition at the double CÍN bond; with arenes and haloarenes, the corresponding C-amidoalkylation products were obtained.     

Spectrophotometric microdetermination of bismuth in organic compounds after oxygen-flask combustion

A method has been developed for the micro and submicro determination of bismuth in organic compounds, based on combustion in an oxygen-filled flask, provided with a silica spiral instead of the conventional platinum holder (which alloys with bismuth). After absorption of the products in hydrochloric acid (1 + 1), the solution is chemically treated to convert the bismuth into the orange-yellow BiI(-)(4) complex, then the absorbance is measured at 465 nm. Analysis of 12 organic compounds containing 28-74% of bismuth yielded satisfactory results with a maximum standard deviation of 0.4%.     

Di- and tri(2-pyron-6-yl)arenes

Condensation of di- and triacetylarenes with 1,1,1,3-tetrachloro-3-alkoxypropanes or ,-dichloroacrolein in acidic media gave a number of (dichloropentadienyl)- and tris (dichloropentadienyl)-substituted aryl ketones, which, in the case of acetic acid in the presence of phosphoric acid, are converted to the corresponding di- and tri(2-pyron-6-yl)arenes. It was observed that nitric acid has an oxidation effect on 2-pyrones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 897–901, July, 1977.     

Syntheses of (-)-Isocitric Acid Lactone and (-)-Homoisocitric Acid. A New Method of Conversion of Alkynylsilanes into the Alkynyl Thioether and Corresponding Carboxylic Acids

A simple, stereoselective synthesis of natural isocitric and homoisocitric acids from a common alkynylsilane correlates the stereochemistry of these acids. Starting with dimethyl D-malate dianion, methyl 2-hydroxy-3-carbomethoxy-6-(trimethylsilyl)-5-hexynoate (6a) was prepared with a good stereoselectivity (threo/erythro 90/10). Oxidative cleavage of the triple bond provided isocitric acid lactone (8') in 15% overall yield starting from D-malic acid diester 1. The synthesis of homoisocitric acid relied on a new method of conversion of alkynylsilane to alkynyl thioether, which is converted to the carboxylic acid of the same chain length. Addition of benzenesulfenyl chloride to (trimethylsilyl)alkyne 6b and elimination of trimethylsilyl chloride gave the corresponding thioether 10, which by acid hydrolysis gave homoisocitric acid (11) in a 24% yield from D-malic acid ester. This novel method of conversion of alkynylsilane to the corresponding acid was illustrated with several other alkynyltrimethylsilanes.     

Synthesis of cross-linked chitosan modified with the glycine moiety for the collection/concentration of bismuth in aquatic samples for ICP-MS determination.

A chelating resin, cross-linked chitosan modified with the glycine moiety (glycine-type chitosan resin), was developed for the collection and concentration of bismuth in aquatic samples for ICP-MS measurements. The adsorption behavior of bismuth and 55 elements on glycine-type chitosan resin was systematically examined by passing a sample solution containing 56 elements through a mini-column packed with the resin (wet volume; 1 ml). After eluting the elements adsorbed on the resin with nitric acid, the eluates were measured by ICP-MS. The glycine-type chitosan resin could adsorb several cations by a chelating mechanism and several oxoanions by an anion-exchange mechanism. Especially, the resin could adsorb almost 100% Bi(III) over a wide pH region from pH 2 to 6. Bismuth could be strongly adsorbed at pH 3, and eluted quantitatively with 10 ml of 3 M nitric acid. A column pretreatment method with the glycine-type chitosan resin was used prior to removal of high concentrations of matrices in a seawater sample and the preconcentration of trace bismuth in river water samples for ICP-MS measurements. The column pretreatment method was also applied to the determination of bismuth in real samples by ICP-MS. The LOD of bismuth was 0.1 pg ml(-1) by 10-fold column preconcentration for ICP-MS measurements. The analytical results for bismuth in sea and river water samples by ICP-MS were 22.9 +/- 0.5 pg ml(-1) (RSD, 2.2%) and 2.08 +/- 0.05 pg ml(-1) (RSD, 2.4%), respectively.     

On-line preconcentration system for bismuth determination in urine by flow injection hydride generation inductively coupled plasma atomic emission spectrometry

An on-line bismuth preconcentration and determination system implemented with hydride generation inductively coupled plasma atomic emission spectrometry (HG-ICP-AES) associated to flow injection (FI) was studied. Quinolin-8-ol and Amberlite XAD-7 were used for the retention of bismuth, at pH 4.5. The bismuth complex was removed from the micro-column with nitric acid. The detection limit value for the preconcentration of 100 ml of aqueous solution was 0.02 ng ml(-1) with a relative standard deviation (R.S.D.) of 3.5%, calculated from the peak heights obtained. The calibration graph using the preconcentration system for bismuth was linear with a correlation coefficient of 0.999 at levels near the detection limits up to at least 100 ng ml(-1). The method was successfully applied to the determination of bismuth in human urine samples.     

Dual-reagent catalysis within Ir-Sn domain: highly selective alkylation of arenes and heteroarenes with aromatic aldehydes

Reactions of arenes and heteroarenes with aromatic aldehydes proceeded smoothly in the presence of a catalytic combination of [Ir(COD)Cl]2-SnCl4 to afford the corresponding triarylmethane derivatives (TRAMs) in high yields. This 100% TRAM selective transformation is clean and eliminates the use of acid systems.     

Amperometry with two polarisable electrodes-XI Determination of bismuth by EDTA titration

Optimum conditions have been found for a highly selective determination of bismuth via EDTA titration with biamperometric indication of the end-point. The influence of the applied potential, pH and stirring on the accuracy and selectivity of the determination has been studied. In a medium of 0.4M nitric acid only high concentrations of iron(III) and copper(II) interfere with the determination of bismuth. Zirconium, thallium(III) and indium interfere even in small concentrations. The average error of the determination of 5-100 mg of bismuth (when titrated with 0.05M EDTA solution) is +/-0-1 % rel. and for the determination of 0.5-10 mg it is +/-0.3% rel. (0.005M EDTA). The method has been verified by the analysis of a Wood's metal of known composition.     

A facile synthesis of natural products chaetomellic acid A and 1,7(Z)- nonadecadiene-2,3-dicarboxylic acid

Synthesis of recently isolated bioactive natural products chaetomellic acid A anhydride (1) and a novel 1,7(Z)-nonadecadiene-2,3-dicarboxylic acid (2) have been described. Chemoselective carbon[bond]carbon S(N)2' coupling reactions of appropriate Grignard reagents with dimethyl bromomethylfumarate (7) in diethyl ether in the presence of HMPA at room temperature furnished the corresponding diesters 8 and 15 in 60-62% yields. The formed diesters 8 and 15 on hydrolysis gave respectively the corresponding desired diacids 9 and 2 in quantitative yields. Acetic anhydride induced ring closure of diacids 9 and 2 respectively gave the chaetomellic acid A anhydride (1) and isochaetomellic acid B anhydride (16) with 38-39% overall yields in five steps.     

Improvement Method for Synthesis of <Emphasis Type="Italic">p-tert</Emphasis>-butylthiacalix[<Emphasis Type="Italic">n</Emphasis>]arenes; Effect of Using Base Catalyst with Carboxylic Acid

The improved method for synthesis of p-tert-butylthiacalix[n]arenes (TCnAs) by using precursor which is sulfur-bridged oligomer of p-tert-butylphenol with acetic acid and terephthalic acid as a template in a combination with base catalyst such as NaOH and NaH gave much better yields for TC6A (10.6 %) and TC8A (7.8 %), respectively. Such stronger base NaH than NaOH could bring down a reaction temperature for synthesis of TC8A.     

Synthesis and Conformational Characteristics of Benzyl-Substituted p-tert-Butylcalixarenes

(m-Methylbenzyloxy)-, bis(p-methylbenzyloxy)-, and bis(m-methylbenzyloxy)-p-tert-butylcalix[4]arenes were prepared by reactions of p-tert-butylcalix[4]arene with p- and m-methylbenzyl bromides in the presence of alkali metal carbonates. Silylation of these derivatives gave (m-methylbenzyloxy)bis(trimethylsilyloxy)-, bis(m-methylbenzyloxy)bis(trimethylsilyloxy)-, and bis(p-methylbenzyloxy)bis(trimethylsilyloxy)-p-tert-butylcalix[4]arenes. With phase-transfer catalysis, bis(p-methylbenzyloxy)bis(2-propenyloxy)- and bis(m-methylbenzyloxy)bis(2-propenyloxy)-p-tert-butylcalix[4]arenes were obtained. Alkylation of the monosubstituted calixarene yields the corresponding trisubstituted derivative.     

Solvation of the bismuth(III) ion by water, dimethyl sulfoxide, N,N'-dimethylpropyleneurea, and N,N-dimethylthioformamide. An EXAFS, large-angle X-ray scattering, and crystallographic structural study

The structure of the solvated bismuth(III) ion in aqueous, dimethyl sulfoxide, N,N'-dimethylpropyleneurea, and N,N-dimethylthioformamide solution has been studied by means of EXAFS and large-angle X-ray scattering (LAXS). The crystal structures of the solid compounds octakis(dimethyl sulfoxide)bismuth(III) perchlorate, [Bi(OS(CH3)2)8](ClO4)3, hexakis(N,N'-dimethylpropyleneurea)bismuth(III) perchlorate, [Bi(OCN2(CH2)3(CH3)2)6](ClO4)3, and nonaaquabismuth(III) trifluoromethanesulfonate, [Bi(H2O)9](CF3SO3)3 (redetermination), have been determined. The aqueous solutions must be strongly acidic, since the hydrated bismuth(III) ion starts to hydrolyze into Bi6O4(OH)4(6+) complexes already at an excess of strong acid at 1.0 mol.dm-3. For very acidic aqueous perchlorate solutions, the LAXS and EXAFS data gave a satisfactory fit for eight-coordination of the bismuth(III) ion, with a mean Bi-O bond distance of 2.41(1) A. The crystal structure of octakis(dimethyl sulfoxide)bismuth(III) perchlorate shows that the bismuth(III) ion coordinates eight dimethyl sulfoxide molecules via the oxygen atoms in a distorted square antiprismatic configuration. The mean Bi-O bond distance is 2.43 A and the mean Bi...S distance 3.56 A. For the dimethyl sulfoxide solution, the corresponding mean distances were found to be 2.411(6) and 3.535(12) A. The N,N'-dimethylpropyleneurea-solvated bismuth(III) ion is octahedrally coordinated in both solid state and solution with the Bi-O bond distances of 2.324(5) and 2.322(3) A, respectively. The bismuth(III) ion is six-coordinated in the sulfur donor solvent N,N-dimethylthioformamide with a mean Bi-S bond distance of 2.794(8) A. A comparison with the structure of the solvated lanthanum(III) ion shows that the bismuth(III) ion is smaller for all coordination numbers. New effective ionic radii for the bismuth(III) ion in different coordination numbers are proposed, based on results in this study and in the literature.