Ce(IV) immobilized on halloysite nanotube–functionalized dendrimer (Ce(IV)–G2): A novel and efficient dendritic catalyst for the synthesis of pyrido[3,2-c]coumarin derivatives

In this study, a new and stable Ce(IV) immobilized on halloysite nanotube–functionalized dendrimer was designed, synthesized, and characterized using Fourier-transform infrared, elemental analysis, thermogravimetric analysis, field emission scanning electron microscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, transmission electron microscopy, dynamic light scattering, Brunauer–Emmett–Teller, and inductively coupled plasma optical emission spectroscopy techniques. This catalyst was efficiently used for the one-pot, single-step multicomponent synthesis of pyrido[3,2-c]coumarins from 4-aminocoumarin, aldehydes, and aryl ketones. The efficiency and selectivity of this catalytic system were also evaluated for the synthesis of pyrido[3,2-c]coumarins from terminal/internal alkynes instead of aryl ketones. In this respect, the regioselectivity of the products was successfully assigned by X-ray crystallographic analysis. All these reactions were best performed under solvent-free conditions in the presence of only 0.28 mol% of the catalyst, and such a one-pot multicomponent synthesis of pyrido[3,2-c]coumarins is reported for the first time. It is also worth noting that single-step and short reaction path for the synthesis of a variety of pyrido[3,2-c]coumarins along with excellent reusability of this dendritic catalyst makes this method economically and environmentally attractive.     

Highly efficient oxidative cleavage of alkenes and cyanosilylation of aldehydes catalysed by magnetically recoverable MIL‐101

The catalytic activity of magnetically recoverable MIL‐101 was investigated in the oxidation of alkenes to carboxylic acids and cyanosilylation of aldehydes. MIL‐101 was treated with Fe₃O₄ and the prepared catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, N₂ adsorption measurements, field emission scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and inductively coupled plasma analysis. The catalytic active sites in this heterogeneous catalyst are Cr³⁺ nodes of the MIL‐101 framework. This heterogeneous catalyst has the advantages of excellent yields, short reaction times and reusability several times without significant decrease in its initial activity and stability in both oxidation and cyanosilylation reactions. Its magnetic property allows its easy separation using an external magnetic field.     

Readily prepared resin-bound 2-pyridinethiol and its application for removal of mercury ions

2-Pyridinethiol attached to commercially available monosize chloromethylated polystyrene was used for selective removal of Hg(II) from aqueous solutions containing different amounts of Hg(II) (10?C100?ppm). The adsorption rate was high at the beginning of the reaction and then equilibrium was reached in about 10?min. The maximum Hg(II) adsorption capacity of this novel and stable resin was about 55.94?mg/g of the dry polymer. The Hg(II) adsorption ability increased with increasing pH, in the range where the solubility of the Hg(II) was not affected by pH. More than 95% of the adsorbed Hg(II) was desorbed in 15?min using 1?M HNO₃ as an elution agent. The regeneration of this resin by strong acid was feasible and desorption ratio was very high (up to 96%).     

Highly efficient protection of alcohols and phenols catalysed by tin porphyrin supported on MIL‐101

The catalytic activity of 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], supported on chloromethylated MIL‐101, was investigated in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) and also their tetrahydropyranylation with 3,4‐dihydro‐2H‐pyran. Excellent yields, mild reaction conditions, short reaction times and reusability of the catalyst without significant decrease in its initial activity are noteworthy advantages of this supported catalyst. Copyright © 2015 John Wiley & Sons, Ltd.     

Catalyst‐Free and Green Synthesis of Some Novel Benzamide Derivatives

In the present work, a simple, green, rapid, and catalyst‐free procedure for the synthesis of benzamide derivatives by ring opening of azlactones with diamines such as ethylene diamine and 1,3‐propylenediamine is described. The present method offers several advantages such as short reaction times, easy work‐up, and mild reaction conditions in the absence of catalyst and any toxic solvent and material. In addition, the structure obtained by X‐ray crystallography was compared with the theoretical results obtained by density functional theory using the B3LYP functional and cc‐pVDZ basis sets.     

C–S Targeted Biodegradation of Dibenzothiophene by Stenotrophomonas sp. NISOC-04

Crude oil-contaminated soil samples were gathered across Khuzestan oilfields (National Iranian South Oil Company, NISOC) consequently experienced a screening procedure for isolating C-S targeted dibenzothiophene-biodegrading microorganisms with previously optimized techniques. Among the isolates, a bacterial strain was selected due to its capability of biodegrading dibenzothiophene in a C-S targeted manner in aqueous phases and medium mostly consisting of separately biphasic water-gasoline. The 16S rDNA of the isolate was amplified using eubacterial-specific primers and then sequenced. Based on sequence data analysis, the microorganism, designated NISOC-04, clustered most closely with the members of the genus Stenotrophomonas. Gas chromatography indicated that Stenotrophomonas sp. NISOC-04 utilizes 82% of starting 0.8 mM dibenzothiophene within a 48-h-long exponential growth phase. Growth curve analysis revealed the inability of Stenotrophomonas sp. NISOC-04 to utilize dibenzothiophene (DBT) as the exclusive carbon or carbon/sulfur source. Gibbs' assay showed no 2-hydroxy biphenyl accumulation, but HPLC confirmed the presence of 2-hydroxy biphenyl as the final product of DBT desulfurization. Under sulfur starvation, Stenotrophomonas sp. NISOC-04 produced a huge biomass with untraceable sulfur and utilized atmospheric insignificant sulfur levels.     

Enhanced Production of Citric Acid in Yarrowia lipolytica by Triton X-100

Various chemical surfactants could affect permeability of yeast cells. In this study, effects of the surfactant addition upon yeast cells permeability and citric acid (CA) production by Yarrowia lipolytica strains DSM 3286 and M7 were investigated. The addition of Triton X-100 increased 1.4-1.8-fold of the maximum CA quantity achieved for both strains, with final CA concentrations ranging between 75-85 g/l that correspond to CA conversion yields per unit of glucose consumed of ~0.80-0.84 g/g. Scanning electron micrographs of yeast cells showed that the cells treated with Triton X-100 had altered cell structure and were smaller and narrower compared with the non-treated ones. The results showed that Triton X-100 could be used in order to increase the efficiency of CA production by Y. lipolytica strains.     

Highly efficient tetrahydropyranylation of alcohols and phenols catalyzed by a new and reusable high-valent vanadium(IV) porphyrin

In the present work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V^IV(TPP)(OTf)₂], in the tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) is reported. This new electron-deficient V(IV) compound was used as a highly efficient catalyst for pyranylation of primary (aliphatic and benzylic), sterically-hindered secondary and tertiary alcohols with DHP. Tetrahydropyranylation of phenols with DHP was also performed to afford the desired THP-ethers. The chemoselectivity of this method was also investigated. The results indicated that primary alcohols are more reactive in the presence of secondary and tertiary alcohols and phenols. This catalyst was reused several times without loss of its activity.