Copper-doped silica cuprous sulfate: A highly efficient heterogeneous nano-catalyst for one-pot three-component synthesis of 1-H-2-substituted benzimidazoles from 2-bromoanilines,aldehydes, and [bmim]N3

A facile and highly efficient one-pot three-component synthesis of 1-H-2-substituted benzimidazole derivatives from readily available substrates catalyzed by copper-doped silica cuprous sulfate (CDSCS) is described. In this method, treatment of diverse 2-bromoanilines, aldehydes, and [bmim]N₃ in DMF at 110 °C in the presence of CDSCS as a highly efficient heterogeneous nano-catalyst affords the corresponding 1-H-2-substituted benzimidazoles in good to excellent yields. The CDSCS is an inexpensive and stable nano-catalyst that could be simply prepared, recovered and reused for many consecutive reaction runs without significant loss of its activity.     

Synthesis, characterization and electrochemical properties of two new calix[4]arene derivatives bearing two ferrocene imine or ferrocene amine units at the upper rim

A novel calix[4]arene derivative with two ferrocenyl Schiff-base groups at the upper rim 3 has been synthesized from 5,17-diformyl-25,27-dipropoxy-26,28-dihydroxy calix[4]arene and 4-ferrocenylaniline via condensation reaction. Reduction of 3 with sodium borohydride led to calix[4]arene derivative 4 with two amino ferrocenyl groups at the upper rim. The ferrocenyl Schiff-base calix[4]arene and its corresponding reduced amine have been purified and characterized by elemental analysis,¹H NMR, FTIR, Mass and UV-vis spectral data. Electrochemical properties of compounds 3 and 4 have been investigated. Cyclic voltammograms of 3 and 4 show reversible redox couples of ferrocene/ferrocinium at E_1/2=0.401 V and 0.346 V, respectively. Electrochemical studies show these redox active compounds electrochemically recognize trivalent lanthanides La³⁺ and Ce³⁺ and divalent Pb²⁺ and Cu²⁺cations. With ferrocenyl Schiff-base calix[4]arene 3 an anodic shift as large as 130 mV is observed on addition of one equivalent of Ce³⁺ ion. Also extraction properties of compound 4 towards some metal cations have been described. It has been observed that compound 4 has a good selectivity for metal cations Fe³⁺, Cu²⁺, Pb²⁺ and Cd²⁺ against Ni²⁺ and Co²⁺.     

A rapid and convenient synthesis of gem-bis(dithiocarbamate) derivatives from primary aliphatic amines,carbon disulfide,and aromatic aldehydes using boron trifluoride-diethyl etherate

An efficient route for the synthesis of gem-bis(dithiocarbamate) derivatives is developed using dithiocarbamic acid salts generated from primary aliphatic amines and CS₂. The method offers high yields, employs mild reaction conditions, and demonstrates excellent functional group compatibility. The structures of the products were confirmed spectroscopically and by X-ray analysis.     

Synthesis of fused hydroxy dihydropyrroles and unexpected dihydropyrazine and dihydroquinoxaline derivatives based on heterocyclic ketene aminals

The one-pot four-component synthesis of highly functionalized fused hydroxyl dihydropyrroles and dihydropyrazines from readily available diamines, 1,1-bis (methylsulfanyl)-2-nitroethene, phenylglyoxal monohydrates, and C-H acids have been developed. This strategy provides an efficient, catalyst-free approach for easy access to various new hydroxyl-dihydropyrrole and dihydropyrazine rings in good to high yields. The products were confirmed by ¹H and ¹³C NMR, IR, mass, and X-ray crystal structure analyses.     

A fuzzy based threshold policy for a single server retrial queue with vacations

In this paper we deal with a single server retrial queue with vacations. The server serves the customers until the system becomes empty, then it takes a vacation. The system consists of two types of costs. The blocking cost is considered whenever a customer is blocked either because of the server is busy or off. There is also a cost each time the server is turned on. The problem is to find an effective policy for turning on the dormant server. We propose a Fuzzy Based Threshold Policy (FBTP) to control the server, substitute for conventional threshold policies. The FBTP is based on four input parameters, an inference stage and it is tuned up using a stochastic List Based Threshold Accepting (LBTA) algorithm. Simulation models are developed to validate the fuzzy controller. Numerical experiments are provided to show that the proposed method is superior to crisp threshold policies.     

Synthesis,crystal structural study and catalyst active of benzyloxycarbonylmethyl triphenylphosphonium hexabromopalladate (II) in amination of aryl halides and Suzuki cross-coupling reaction

In this study, palladium (II) chloride reacted with the phosphonium salt [PhCH₂COOCH₂P(Ph)₃]Br to give [PhCH₂COOCH₂P(Ph)₃]₂[Pd₂Br₆] (1). The characterization of synthesized compound was performed by elemental analysis, FT-IR, ¹H, ³¹P, ¹³C NMR and also X-ray crystallography. It was found that this compound works as an efficient catalyst for the amination of aryl halides to afford primary amines, the results of which were satisfactory. Furthermore, it was found that the catalyst showed a high activity for Suzuki carbon–carbon cross-coupling of aryl halides and phenylboronic acid. Interestingly, the catalyst can be recovered from the reaction mixture and recycled four consecutive runs without any significant loss in activity.     

Thulium(III) Ions Monitoring by a Novel Thulium(III) Microelectrode Based on a S‐N Schiff Base

This study presents for the first time development of a highly selective and sensitive thulium(III) micro‐sensor. Theoretical calculations were conducted on a S‐N Schiff base [thiophene‐2‐carbaldehyde‐(7‐methyl‐1,3‐benzothiazol‐2‐yl) hydrazone] (TCMH) in order to obtain a clue about the tendency of TCMH to Tm(III) and some other metal ions. Then, TCMH was used as a membrane‐active component to prepare a Tm(III)‐selective polymeric membrane microelectrode. In line with the resulting data, the electrode exhibits a Nernstian response toward Tm(III) ions for a very wide concentration range (1.0×10^?11–4.0×10^?6 M) with a detection limit of 1.0×10^?11 (ca. 1.5 ppt) and a very fast response time in the whole concentration range (<5 s). In addition, the results showed that the certain microelectrode could be applied in the pH range of 4.0–11.0 with a usage of more than one month without any considerable potential divergence.     

Synthesis and X‐ray structural characterization of a bidendate phosphine (dppe) palladium(II) complex and its application in Stille and Suzuki cross‐coupling reactions

The synthesis, characterization, crystal structure and catalyst activity of the bidentate phosphine complex [1,2‐bis(diphenylphosphino)ethane]palladium(II) bromide, [PdBr₂(dppe)], are presented. Treatment of 1,2‐bis(diphenylphosphino)ethane with palladium(II) bromide under mild conditions resulted in the compound in high yield and purity. The characterization of the synthesized compound was performed using spectroscopic methods, such as Fourier transform infrared and NMR, CHN analysis and X‐ray crystallography. The structure of the compound was slightly distorted square planar. This compound was found to work as an efficient catalyst for both Stille and Suzuki cross‐coupling reactions of various aryl halides with triphenyltin chloride and/or phenylboronic acid. Also, the catalyst could be recovered and reused several times without significant loss of its catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,spectral characterization,X-ray crystal structure,electrochemical studies,and DNA interactions of a Schiff base pro-ligand and its homobimetallic complexes containing the cysteamine moiety

A Schiff base, N,N′-(3,4-dithiahexane-1,6-diyl)bis(5-methylsalicylideneimine), was synthesized and characterized by X-ray crystallography. Dimeric complexes of nickel(II), palladium(II), and vanadium(IV) were synthesized by the reactions of the Schiff base with nickel(II) acetate, palladium(II) acetate, and vanadyl acetylacetonate in 1:1 molar ratio. In all three complexes, the thiol group was deprotonated and coordinated to the metal. The X-ray structure of the Schiff base showed that in the crystalline form, the SH groups were oxidized to the corresponding disulfide. In the dimeric complexes, coordination took place through the azomethine nitrogen, enolic oxygen, and sulfur atoms. The metal-to-ligand ratio was 1:1, and molar conductance data revealed that the metal complexes were nonelectrolytes. The free Schiff base and its complexes showed photoluminescence in methanol at room temperature. The redox behavior of the compounds was studied by cyclic voltammetry in DMF, which showed both quasi-reversible and irreversible processes. The interaction of the complexes with DNA was investigated by electronic absorption spectroscopy.