Enhancement of catalytic activity in the synthesis of 2-amino-4H-chromene derivatives using both copper- and cobalt-incorporated magnetic ferrite nanoparticles

Research on Chemical Intermediates - Cu0.5Co0.5Fe2O4 magnetic nanoparticles were prepared, characterized and employed as bench-top, highly active and magnetically separable nanocatalysts for the...     

Synthesis and antibacterial activity of new N-[2-(thiophen-3-yl)ethyl] piperazinyl quinolones

As a part of continuing search for potential antibacterial agents in the quinolones field, we have synthesized novel quinolone agents bearing N-[2-(thiophen-3-yl)ethyl] piperazinyl moiety in the 7-position of the quinolone ring. In vitro antibacterial evaluation of the target compounds showed that N-[2-(thiophen-3-yl)ethyl] group attached to piperazine ring served as promising C-7 substituent for piperazinyl quinolone antibacterials. Among these derivatives, ciprofloxacin analogues, containing N-[2-(thiophen-3-yl)-2-hydroxyiminoethyl] or N-[2-(thiophen-3-yl)-2-methoxyiminoethyl] residue provided a high inhibition against all the tested Gram-positive organisms including methicillin-resistant Staphylococcus aureus comparable or superior with respect to the reference drugs norfloxacin and ciprofloxacin.     

Local discontinuous Galerkin approximations to fractional Bagley-Torvik equation

In this research, numerical approximation to fractional Bagley-Torvik equation as an important model arising in fluid mechanics is investigated. Our discretization algorithm is based on the local discontinuous Galerkin (LDG) schemes along with using the natural upwind fluxes, which enables us to solve the model problem element by element. This means that we require to solve a low-order system of equations in each subinterval, hence avoiding the need for a full global solution. The proposed schemes are tested on a range of initial- and boundary-value problems including a variable coefficient example, a nonsmooth problem, and some oscillatory test cases with exact solutions. Also, the validation of the proposed methods was compared with those obtained available existing computational procedures. Overall, it was found that LDG methods indicated highly satisfactory performance with comparatively lower degree of polynomials and number of elements compared with other numerical models.     

A needle trap device packed with MIL-100(Fe) metal organic frameworks for efficient headspace sampling and analysis of urinary BTEXs

The aim of this study was to develop a new method for the determination of benzene, toluene, ethylbenzene and xylene isomers (BTEXs) in urine samples. In this method, MIL-100(Fe)@Fe₃O₄@SiO₂ metal–organic framework was synthesized, characterized and packed inside a needle trap device (NTD) as a sorbent for headspace extraction of unmetabolized BTEXs from urine samples followed by gas chromatography (GC) analysis. The GC device was equipped with a flame ionization detector (FID). The results showed that the optimal extraction time, extraction temperature and salt content were 60 min, 30°C and 5%, respectively. Also, the optimal desorption time and temperature were determined to be 1 min and 250°C, respectively. The limits of detection and quantification of the analytes of interest were in the ranges 0.0001–0.0005 and 0.0003–0.0014 μg ml⁻¹, respectively. The intra- and inter-day repeatability were <7.6%. The accuracy of the measurements in urine samples was in the range 7.1–11.4%. The results also demonstrated that the proposed NTD offered various advantages such as having high sensitivity and being inexpensive, reusable, user friendly, environmentally friendly and compatible for use with the GC device. Therefore, it can be efficiently used as a MIL–NTD for the extraction and analysis of unmetabolized BTEXs from urine samples.     

One-Pot and Solvent-Free Synthesis of 1,4-Dihydropyridines and 3,4-Dihydropyrimidine-2-ones Using New Synthetic Recyclable Catalyst via Biginelli and Hantzsch Reactions

Pyridine dicarboxylic acid guanidine–cobalt complex (PDAG-Co) (3) catalyzes one-pot, three-component coupling of aldehydes, β-dicarbonyl compounds, and ammonium acetate to afford the corresponding 1,4-dihydropyridines (1,4-DHPs) via Hantzsch reaction. 3,4-Dihydropyrimidine-2-ones (3,4-DHPMs) and their sulfur analogs are also synthesized under the same conditions via Biginelli condensation protocol. The catalyst is reusable at least five times, highly efficient, easily prepared, and used under mild reaction conditions.

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

Efficient One‐Pot Synthesis of Bis(4‐hydroxycoumarin)methanes in the Presence of Sulfonic Acid Functionalized Nanoporous Silica (SBA‐Pr‐SO3H)

An efficient and simple method for the synthesis of bis(4‐hydroxycoumarin)methanes has been achieved through a one‐pot condensation of aryl aldehydes and 4‐hydroxycoumarin in the presence of nanoporous solid acid catalyst of SBA‐Pr‐SO₃H with pore size of 6 nm. Excellent yields, short reaction times, reusability of the catalyst and simple workup are advantages of this synthetic procedure.     

Efficient Three-Component Synthesis of 4-Aminoquinazolines

4-Aminoquinazolines were synthesized in good yields via a one-pot, three-component reaction of anthranilonitrile, acylchlorides, and ammonium acetate in the presence of catalytic amounts silica-supported Preyssler nanoparticles under refluxing conditions.     

Hybrid-DFT Study and NBO Interpretation of the Configurational Behavior of 2-Halotetrahydrothiopyran S-Oxides

Abstract

Natural bond orbital (NBO) interpretation and hybrid density functional theory (hybrid-DFT: B3LYP/Def2-TZVPP)-based methods were used to investigate the impacts of the generalized anomeric effects (GAE), electrostatic, and steric interactions on the conformational properties of cis and trans isomers of 2-fluoro-, 2-chloro-, and 2-bromotetrahydrothiopyran S-oxide (1–3). The results obtained showed that the trans-axial configurations are the most stable forms of compounds 1–3. Based on the results obtained, the instability of the second lowest energy-minimum (cis-equatorial configuration, with axial S?O and equatorial C?X bonds, X = halogen atoms) increases from compound 1 to compound 3. This trend is also observed for the third lowest energy-minimum (i.e., the trans-equatorial configuration). Contrary to the trend observed for the cis- and trans-equatorial forms, the instability of the cis-axial form compared to the trans-axial form, increases from 1 to 2 but decreases slightly from 2 to 3. The correlations between the GAE, bond orders, steric effects, ΔG, Δμ, structural parameters, and conformational and configurational behaviors of compounds 1–3 have been investigated.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.