Electrochemical Assay of Methyl Parathion in Homogeneous Reaction Using Water Soluble Films with Immobilized Acetylcholinesterase

Water soluble poly (vinyl alcohol) (PVA) was used to prepare the enzyme membranes of acetylcholinesterase (AChE) for electrochemical assaying methyl parathion in water insoluble organic solvent. The immobilized enzyme was separated from electrode for the development of enzyme inhibition-based bioassays. This assay is simple and convenient where enzyme membrane is applicable for single use and the electrode for repeated use. The enzyme membranes can be used handily piece by piece and the released AChE performs catalytic reaction homogeneously. The inhibition percentage of AChE increases with the concentration of methyl parathion ranging from 0.1 to 1 mg/mL.     

NONCONVENTIONAL FRIEDEL-CRAFTS CHEMISTRY II. ON THE CATALYTIC ACTION OF TRIFLIC ACID AND ALUMINIUM CHLORIDE ON SELECTED ARYL THIOESTERS

Abstract

The catalytic action of triflic acid and/or aluminium chloride on seven selected aryl thioesters (1-7) gave in all cases aryl thiols, diaryl sulfides, diaryl disulfide, and thianthrene derivatives in addition to the corresponding aryl carboxylic acids. Thioester 5 gave thiochromanone derivatives in good yield under the same conditions. Plausible mechanisms were suggested to rationalize the obtained results.     

RuCl3-Catalyzed Regioselective Diarylation with Aryl Tosylates via C-H Activation

The direct arylation of arylpyridines with aryl tosylates was carried out smoothly in the presence of 2.5 mol% RuCl₃ using MesCOOH as crucial promoter to generate biarylated products. The method is simple, efficient, safe, and regioselective, can be performed in the absence of expensive ligands, and does not require any precautions with regard to the exclusion of air and moisture. The biarylated products were obtained in good yields.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Aryl Radical Cyclization: Regioselective Synthesis of 6a,7,8,12b‐Tetrahydro‐6H‐chromeno[3,4‐c]quinolin‐6‐one

Regioselective synthesis of 6a,7,8,12b‐tetrahydro‐6H‐chromeno[3,4‐c]quinolin‐6‐ones 4 in good to excellent yields from 3‐(2‐bromoanilinomethyl)coumarins 3 by aryl radical cyclization is described. The cyclization precursors 3 were prepared by the reaction of 3‐chloromethyl coumarin with different 2‐bromoaniline.     

Suzuki–Miyaura Reaction of Unactivated Aryl Chlorides Using Benzimidazol‐2‐Ylidene Ligands

Abstract

Four functionalized bis(benzimidazolium) salts (2a–d) have been prepared and characterized by conventional spectroscopic methods and elemental analyses. A highly effective, easy to handle, and environmentally bengin process for palladium‐mediated Suzuki cross‐coupling was developed. The in situ prepared three‐component system Pd(OAc)₂/bis(benzimidazolium) bromides (2a–d) and Cs₂CO₃ catalyzes quantitatively the Suzuki cross‐coupling of deactivated aryl chloride in aqueous media.     

Synthesis of trifluoromethylated heterocycles using partially fluorinated epoxides

Reaction of 2-trifluoromethyl- (1) and 2,2-bis(trifluoromethyl)- (2) oxiranes with a variety of sulfur nucleophiles proceeds rapidly and under mild conditions. For example, epoxide 2 reacts with aqueous solution of Na₂S, producing S[CH₂C(CF₃)₂OH]₂. Reaction of 2 with Na₂S₂O₃ leads to the formation of the corresponding Bunte salt. Interaction of 2 with NaSCN in water proceeds exothermically and results in high-yield formation of cyclic imine 5. Although this material can be isolated, it has limited stability and undergoes cyclotrimerization at ambient temperature, giving the corresponding 1,3,5-triazine. A number of heterocyclic compounds containing pendant -CH₂C(CF₃)₂OH group were prepared by the reaction of the corresponding thio-derivatives, such as pyridine-2-thiole with epoxide 2. It was found that fluoride anion catalyzes the reaction of epoxides 1 and 2 with isothiocyanates carrying electron withdrawing groups at nitrogen. The reaction results in nucleophilic cyclization and formation of the corresponding exocyclic imines containing a 1,3-oxothiolane moiety. Carbon disulfide was also found to be active in this process, reacting with epoxides 1 and 2 at ambient to give the corresponding trifluoromethylated 1,3-oxathiolane-2-thiones in 58-65% yield.     

A new method for the synthesis of N-substituted 1,3,5-dithiazinanes via the catalytic recyclization of 1,3,5-trithiane with aryl(benzyl) hydrazines and aryl amines

An efficient method for the synthesis of N-substituted 1,3,5-dithiazinanes based on the amination reaction of 1,3,5-trithiane with aryl(benzyl) hydrazines and N-aryl amines in the presence of Ti and Fe catalysts has been developed.     

Reductive carbonylation of aryl and heteroaryl iodides using Pd(acac)2/dppm as an efficient catalyst

Palladium catalyzed simple and efficient protocol for reductive carbonylation of aryl and heteroaryl compounds has been developed. The formylation of aryl and heteroaryl iodides takes place in the presence of Pd(acac)₂/dppm catalyst at 10 bar pressure of synthetic gas to give the desired aromatic and heteroaromatic aldehydes in good to excellent yields. Easy work-up, stability of the catalyst, low catalyst loading and less reaction time are the advantages of this method.     

Electrophilic organic selenium reagents—protonated seleninic acids as precursors for unsymmetrical aromatic selenides

Arylselenylations of methylbenzenes, methoxybenzenes and thiophene were smoothly achieved with selenenium ions generated by comproportionation of 1:1 mixtures of p-toluenesulfonic acid salts of seleninic acids and the corresponding diselenides. A series of p-toluenesulfonic salts of seleninic acids were prepared by hydrogen peroxide oxidation of the corresponding diselenides in the presence of p-toluenesulfonic acid. Novel 2-(organylseleno)thiophenes were obtained by heating the protonated seleninic acids with a 50-fold excess of thiophene in glacial acetic acid.     

ipso-Fluorination of aryltrimethylsilanes using xenon difluoride

Reaction of aryltrimethylsilanes with xenon difluoride in C₆F₆/Pyrex^® at room temperature gives aryl fluorides in good yield. The reaction is inhibited when acetonitrile is used as solvent but proceeds well in CFCl₃/Pyrex^® or CH₂Cl₂/Pyrex^®. Pyrex^® appears to be a very effective heterogeneous catalyst for this ipso-fluorination. The reaction does not proceed in PTFE, quartz, soda glass or glassy-carbon flasks or Pyrex^® flasks pre-rinsed with 2 M NaOH. Aryltrimethylstannanes and arylboronic acids and their esters do not undergo ipso-fluorination under similar conditions. Plausible mechanisms involving electrophilic addition of polarised xenon difluoride [FXe^δ+?F→Pyrex^δ−] followed by ligand coupling are discussed.