Based on MFe2O4 (M=Co,Cu, and Ni): Magnetically recoverable nanocatalysts in synthesis of heterocyclic structural scaffolds

Abstract

Catalysis research under magnetically recoverable nanocatalysts is a well-known topic in organic synthesis. In recent times, catalysis research has clearly experienced a renaissance in the area of utility of ferrite nanoparticles based on their ability to recovery and reusability. In this review, the focus is on the fabrication, characterization and of application the MFe₂O₄ (M=Co, Cu, and Ni) nanocatalysts in synthesis of heterocyclic structural scaffolds.     

Domino "[3+3]-cyclization-homo-Michael" reactions of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes

The Lewis acid mediated domino "[3+3]-cyclization-homo-Michael" reaction of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes allows an efficient one-pot synthesis of functionalized salicylates containing a halogenated side chain. A great variety of substitution patterns could be realized by variation of the starting materials and of the Lewis acid. The mechanism of the domino process was studied.     

Magnetically reusable nanocatalysts in biginelli synthesis of dihydropyrimidinones (DHPMs)

Abstract

Molecules containing dihydropyrimidinone (DHPMs) structures are very important in pharmaceutical and medicinal chemistry due to their excellent biological activities application in synthesis of natural products. Biginelli condensation reaction between an aldehyde, urea/thiourea and a carbonyl compound is the most popular strategy for the synthesis of dihydropyrimidinones. Magnetic recoverable nanocatalysts can be readily separated from reaction medium by using an external magnet, without the need for filtration, centrifugation or other tedious workup processes. In recent times, the catalytic potential of magnetically recoverable nanocatalysts was evaluated in a variety of Biginelli reactions. In this review, we focus on the application of magnetically recoverable gold nanocatalysts in Biginelli synthesis of dihydropyrimidinone derivatives.     

Exogenous Application of Green Titanium Dioxide Nanoparticles (TiO2 NPs) to Improve the Germination,Physiochemical, and Yield Parameters of Wheat Plants under Salinity Stress

Agriculture is the backbone of every developing country. Among various crops, wheat (Triticum aestivum L.) belongs to the family Poaceae and is the most important staple food crop of various countries. Different biotic (viruses, bacteria and fungi) and abiotic stresses (water logging, drought and salinity) adversely affect the qualitative and quantitative attributes of wheat. Among these stresses, salinity stress is a very important limiting factor affecting the morphological, physiological, biochemical attributes and grain yield of wheat. This research work was carried out to evaluate the influence of phytosynthesized TiO₂ NPs on the germination, physiochemical, and yield attributes of wheat varieties in response to salinity. TiO₂ NPs were synthesized using TiO₂ salt and a Buddleja asiatica plant extract as a reducing and capping agent. Various concentrations of TiO₂ nanoparticles (20, 40, 60 and 80 mg/L) and salt solutions (NaCl) (100 and 150 mM) were used. A total of 20 mg/L and 40 mg/L improve germination attributes, osmotic and water potential, carotenoid, total phenolic, and flavonoid content, soluble sugar and proteins, proline and amino acid content, superoxide dismutase activity, and reduce malondialdhehyde (MDA) content at both levels of salinity. These two concentrations also improved the yield attributes of wheat varieties at both salinity levels. The best results were observed at 40 mg/L of TiO₂ NPs at both salinity levels. However, the highest concentrations (60 and 80 mg/L) of TiO₂ NPs showed negative effects on germination, physiochemical and yield characteristics and causes stress in both wheat varieties under control irrigation conditions and salinity stress. Therefore, in conclusion, the findings of this research are that the foliar application of TiO₂ NPs can help to improve tolerance against salinity stress in plants.     

SOLVENT-FREE CONVERSION OF OXIRANES TO THIIRANES WITH THIOUREA

A simple and efficient method for the conversion of various oxiranes to the corresponding thiiranes using thiourea under solvent free conditions is described.     

Cobalt titanate–cobalt oxide composite thin films deposited from heterobimetallic precursor

A single molecular heterobimetallic complex, [Co₂Ti(μ₃‐O)(TFA)₆(THF)₃] (1) [TFA = trifluoroacetate, THF = tetrahydrofuran], was synthesized, structurally and spectroscopically characterized and implemented as a single‐source precursor for the preparation of CoTiO₃–CoO composite thin films by aerosol‐assisted chemical vapour deposition (AACVD). The precursor complex was prepared by interaction of Co(OAc)₂.4H₂O [OAc = (CH₃COO^?)] with Ti(iso‐propoxide)₄ in the presence of trifluoroacetic acid in THF, and was analysed by melting point, CHN, FT‐IR, single‐crystal X‐ray diffraction and thermogravimetric analysis. The precursor complex thermally decomposed at 480 °C to give a residual mass corresponding to a CoTiO₃–CoO composite material. Good‐quality crystalline CoTiO₃–CoO composite thin films deposited at 500 °C by AACVD and characterized through powder X‐ray diffraction and scanning electron microscopy/energy‐dispersive X‐ray spectroscopy show that the crystallites have a rose‐flower‐like morphology with an average petal size in the range of 2–6 µm. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly Regio- and Stereoselective Synthesis of β-Halohydrins from Epoxides Catalyzed with Ceric Ammonium Nitrate

Ce(IV) as ceric ammonium nitrate can effectively catalyze ring opening of epoxides with halides under very mild conditions and easy procedure to give the corresponding β-chloro-and β-bromohydrins in excellent yields. The reactions occur with both substituted and unsubstituted quaternary ammonium halides and with high regio- and stereoselectivity. The reaction of optically active styrene oxide with chloride ion was found to be highly stereospecific and afforded the corresponding β-halohydrin in 96% ee.     

A bound on the Wasserstein-2 distance between linear combinations of independent random variables

We provide a bound on a distance between finitely supported elements and general elements of the unit sphere of ${?}^2\left({\mathbb{N}}^1\right)$. We use this bound to estimate the Wasserstein-2 distance between random variables represented by linear combinations of independent random variables. Our results are expressed in terms of a discrepancy measure related to Nourdin–Peccati’s Malliavin–Stein method. The main application is towards the computation of quantitative rates of convergence to elements of the second Wiener chaos. In particular, we explicit these rates for non-central asymptotic of sequences of quadratic forms and the behavior of the generalized Rosenblatt process at extreme critical exponent.     

Measurement of thermal lensing effects in high power thin disk laser

Two different experimental methods for disk characterization in thin disk lasers are investigated in this paper. First method is based on the stability regions in optical resonator and the second method is based on using an expanded probe beam. Both of the mentioned techniques are used to determine the thermal lensing effects in high power thin disk laser. The results of the experiments are presented and analyzed. Also the advantages and disadvantages of each method are explained.     

Alenush Terian: The Iranian Solar Mother

We present a biographical sketch of Alenush Terian, the first Iranian woman physicist, who was known as the Iranian Solar Mother, since she founded the first solar telescopic observatory in Iran. She taught and carried out astronomical research for three decades with inadequate resources but with unflinching devotion, motivated by a strong desire to propagate scientific education and research in her country.