Trimethylsilylation of Alcohols and Phenols,and Direct Acetylation of Silyl Ethers Catalyzed by Fe(ClO4)3.6H2O

In this article, a mild and efficient protocol for the trimethylsilylation of various aliphatic and benzylic alcohols and phenols with trimethylsilyl chloride using a catalytic amount of ferric perchlorate at room temperature and relatively short reaction times in good to excellent yields is reported. Direct acetylation of trimethylsilyl ethers catalyzed with Fe(ClO ₄ ) ₃ .6H ₂ O(0.02 mmol)/Fe(ClO ₄ ) ₃ SiO ₂ (0.2 g) using acetic anhydride at ambient temperature is also reported.     

Nano catalytic synthesis of flavanone phosphonates using domino Knoevenagel-phospha-Michael route

Abstract

Novel derivatives of diethyl (4-oxo-2-phenylchroman-3-yl) methyl phosphonate have been synthesized under optimal conditions using domino-Knoevenagel-phospha-Michael reaction catalyzed by nano-zinc oxide. The combination of recovery and reusability of catalyst, simple and applicable approach, good reaction time and good yields of products make this method as a suitable route for this purpose. The structures of the products were determined by FT-IR, ¹H-, ¹³C- and ³¹P- Nuclear Magnetic Resonance spectroscopies, and elemental analysis.     

A computational investigation of the electronic properties of Octahedral Al n N n and Al n P n cages (n = 12, 16, 28, 36, and 48)

Density functionla theory (DFT) calculations are performed to characterize geometric and electronic features of the octahedral Al _n N _n and Al _n P _n cages (n = 12, 16, 28, 32, and 48). Toward this aim, ¹⁵N, ²⁷Al, and ³¹P chemical shielding (CS) tensors as well as natural charge analyses are calculated for the optimized structures. CS parameters detect three distinct electronic environments for atoms within the Al _n N _n and Al _n P _n cages. The chemical shifts of N2 sites belonging to a hexagon and surrounded by three hexagons and a square obtained are different from those of N3 sites belonging to a hexagon that is surrounded only by hexagons—due to different curvatures exerted at the sites with different local structures. In addition, there is an increasing tendency in the Δσ values of the three local structures, Δσ (N1) > Δσ (N2) > Δσ (N3), N1 sites belonging to four-membered rings. The chemical shieldings of those Al and P sites belonging to a hexagon that is surrounded only by hexagons in the cages (360.7–366.7 and 496.5–514.7 ppm) are close to those previously reported for AlP nanotubes. Three distinct electrostatic environments around the N, Al, and P nuclei are also confirmed by the calculated natural charges. It should be noted that the positively charged Al atoms on the cages turn out to be the available sites for adsorption of H2 molecules.     

pTSA-catalyzed condensation of xylenols and aldehydes under solvent-free conditions: One-pot synthesis of 9H-xanthene or bisphenol derivatives

A simple and efficient procedure for the synthesis of 9H-xanthene or bisphenol derivatives has been developed by one-pot condensation of xylenols with aromatic aldehydes in the presence of p-toluenesulfonic acid (pTSA) as a catalyst under solvent-free conditions at 100 °C. It is noteworthy that the condensation reaction of 3,5-xylenol with aldehydes produces 9H-xanthene derivatives, while the reaction with other xylenols leads to the corresponding bisphenol derivatives. Different types of aromatic aldehydes are used in the reaction and in every case the products were obtained in good to excellent yields. The structures of these compounds were established on the basis of IR, ¹H NMR, ¹³C NMR and CHN data.     

Lanthanum-selective sensors based on 3-amino-2-mercapto-3H-quinazolin-4-one in PVC matrix

A new solvent polymeric membrane (PME) and coated graphite (CGE) electrodes based on 3-amino-2-mercapto-3H-quinazolin-4-one as a suitable carrier for La(III) ion are described. The sensors exhibited a Nernstian response for La(III) ion over a wide concentration range (3.0 × 10^?7 to 1.0 × 10^?1 M for PME and 1.0 × 10^?7 to 1.0 × 10^?1 M for CGE) with a slope of 20.1 ± 0.3 (PME) and 23.4 ± 0.4 (CGE) mV decade^?1. The lower detection limits by PME and CGE were 2.0 × 10^?7 and 7.1 × 10^?8 M, respectively. The potentiometric response of the proposed electrodes was independent of the pH of the test solution in the pH range 3.0–9.0 with a fast response time (<10 s). The applications of prepared sensors were demonstrated in the determination of lanthanum ions in spiked water sample and also utilized for indirect determination of fluoride content of two mouth wash preparation samples.     

A green and efficient procedure for one-pot synthesis of xanthenes and acridines using silica boron–sulfuric acid nanoparticles (SBSANs) as a solid Lewis-protic acid

Silica boron–sulfuric acid nanoparticles (SBSANs) as a solid Lewis-protic acid have been found to be an efficient heterogeneous catalyst in the synthesis of xanthene and acridine derivatives. The SBSAN-catalyzed reaction between carbonyl compound (aldehyde/ketone/ethyl orthoformate) and 5,5-dimethyl-1,3-cyclohexanedione (dimedone) for synthesis of xanthene derivatives is performed under mild conditions with the excellent isolated yield. Also, we can apply a broad scope of carbonyl compounds and amines for efficient synthesis of various acridine derivatives in the presence of SBSAN catalyst. In these multicomponent approaches the SBSAN catalyst can be reused for several times without any treatment in its catalytic activity.     

Speciation Analysis of Cr(III) and Cr(VI) after Solid Phase Extraction Using Modified Magnetite Nanoparticles

A new solid phase extraction (SPE) method has been developed for the speciation of Cr(III) and Cr(VI). This method is based on the adsorption of Cr(VI) on modified alumina‐coated magnetite nanoparticles (ACMNPs). Total chromium in different samples was determined as Cr(VI) after oxidation of Cr(III) to Cr(VI) using H₂O₂. The chromium concentration has been determined by flame atomic absorption spectrometric (FAAS) technique and amount of Cr(III) was calculated by substracting the concentration of Cr(VI) from total chromium concentration. The effect of parameters such as pH, amount of adsorbent, contact time, sample volume, eluent type, H₂O₂ concentration and cetyltrimethylammonium bromide (CTAB) concentration as modifier on the quantitative recovery of Cr(VI) were investigated. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation (RSD) of Cr(VI) were 140 (for 350 mL of sample solution), 0.083 ng mL^?1, 0.1‐10.0 ng mL^?1 and 4.6% (for 5.0 ng mL^?1, n = 7), respectively. This method avoided the time‐consuming column‐passing process of loading large volume samples in traditional SPE through the rapid isolation of CTAB@ACMNPs with an adscititious magnet. The proposed method was successfully applied to the determination and speciation of chromium in different water and wastewater samples and suitable recoveries were obtained.     

Determination of Hg(II) in Environmental Water Samples Using DLLME Method Prior to GC-FID

Mercury exists in two forms in environment, inorganic salts and organic compounds. Determination of mercury is very important, due to its health effects. In the present research, diphenylation of mercury using phenylboronic acid as a derivatization reagent was used for the determination of Hg(II) in real water samples. A simple, rapid and cheap method named dispersive liquid–liquid microextraction was used for the extraction of analyte under the following conditions: extraction solvent 16 μL of carbon tetrachloride, disperser solvent 1 mL of ethanol and sample volume 5 mL. Under the optimal conditions, the enrichment factor for diphenylmercury was 931 and the limit of detection calculated on the basis of five replicates was 0.004 μg mL^?1. The repeatability of the method expresses as relative standard deviation was 5.1 (n = 6). The linear range was between 0.01 and 10 μg mL^?1. The performance of the proposed technique was evaluated for the determination of mercury in different environmental water samples.     

Synthesis of Novel Organosilicon Compounds Possessing Fully Substituted Imidazole Nucleus Sonocatalyzed by Fe-Cu/ZSM-5 Bimetallic Oxides

An efficient four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described by one-step condensation of an aldehyde, benzil, ammonium acetate, and primary aromatic amine with nanostructure Fe-Cu/ZSM-5 bimetallic oxides in water under ultrasonic irradiation. The short reaction time, good yields, environmental friendly procedure, mild reaction conditions, and convenient operation are important advantage of this protocol. The products generated during the study have been utilized as substrates for synthesis of organosilicon-containing imidazoles. Synthesis of tris(triorganosilyl)methylimidazole derivatives were carried out using organolithium reagent (Me₃Si)₃CLi, prepared via metalation of (Me₃Si)₃CH with methyllithium in tetrahydrofuran, in excellent yields.