A ceric ammonium nitrate based oxidative cleavage pathway for the asymmetric aldol adducts of oxadiazinones derived from (1R,2S)-N-p-methoxybenzylnorephedrine

An N₄-p-methoxybenzyloxadiazinone has been prepared from (1R,2S)-norephedrine through a process of reductive amination, N-nitrosation, reduction, and cyclization. The oxadiazinone was acylated and employed in the asymmetric aldol addition reaction with aromatic and aliphatic aldehydes to yield aldol adducts in isolated yields ranging from 54% to 90%. Selected aldol adducts were treated with ceric ammonium nitrate in aqueous acetonitrile to afford the desired β-hydroxycarboxylic acids through a tandem process of oxidative cleavage of the N₄-p-methoxybenzyl group and acidic hydrolysis of the N₃-acyl side chain. The β-hydroxycarboxylic acids were recovered in high diastereomeric purity as determined by 500 MHz ¹H NMR spectroscopy and the absolute configuration was confirmed by polarimetry. The chiral auxiliary unit, the 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one (oxadiazinone), was converted into its corresponding 3,6-dihydro-2H-1,3,4-oxadiazin-2-one (oxadiazinone) through an oxidative pathway promoted by the ceric ammonium nitrate.     

Synthesis of novel rhodanine based functionalized furans from the reaction of tert-butyl isocyanide with acetylenic esters in the presence of rhodanine acetic acid derivatives

The reactive 1:1 intermediate produced from the reaction of tert-butyl isocyanide and dialkyl acetylenedicarboxylates was trapped by rhodanine-N-acetic acid derivatives to generate polyfunctionalized furan rings in fairly good yields.     

Pistacia integerrima gall extract mediated green synthesis of gold nanoparticles and their biological activities

This paper reports a rapid, facile and one-pot synthesis of environmentally safe gold nanoparticles capped and stabilized with galls extract of Pistacia integerrima. The aqueous gold ions when exposed to P. integerrima galls extract were rapidly reduced as evident from abrupt color change to ruby red, suggesting the biosynthesis of gold nanoparticles (Au-NPs) which were further characterized by UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). Their stability was evaluated against varying pH and different volumes of sodium chloride (NaCl) as well as at a range of temperature (20–80 °C). Au-NPs were tested for enzyme inhibition, antibacterial, antifungal, antinociceptive, muscle relaxant and sedative activities. The UV–Vis spectra of the gold nanoparticles gave surface plasmon resonance at 540 nm while the SEM analysis revealed the particle size in the range of 20–200 nm. FTIR spectra confirmed the involvement of amines, amide groups and alcohols in capping and reduction of gold nanoparticles. Au-NPs showed remarkable stability in different NaCl and pH solutions as well as at elevated temperature. Au-NPs have good antifungal activity and possessed antinociceptive and muscle relaxant properties as observed from their zone of inhibition and significant attenuation of acetic acid induced writhing and reduction of time spent on the rota rod respectively. These results concluded that the gall extract of P. integerrima is a very good bioreductant for the synthesis of gold nanoparticles that have potential for various biomedical and pharmaceutical applications.     

Effect of pulegone and pulegone oxide on the corrosion of steel in 1 <Emphasis Type="Italic">M</Emphasis> HCl

The inhibitive action of pulegone and pulegone oxide toward acid corrosion of steel in molar hydrochloric acid was studied by weight loss measurements, potentiodynamic polarization, and impedance spectroscopy (EIS) methods. The pulegone is extracted starting from oil of Pennyroyal Mint (Mentha pulegium). The natural compound was found to delay the corrosion rate. The pulegone oxide is prepared by oxidation of pulegone. The inhibition efficiency was found to increase with the inhibitor content to attain 81 and 75% at 5 g dm⁻³ for pulegone and pulegone oxide. The increase in temperature leads to an increase in the inhibition efficiency of the natural compared. Correspondence: Belkheir Hammouti, Laboratoire de chimie Appliquée & Environnement, Faculté des Sciences, B.P. 717, 60000 Oujda, Morocco.     

New approach to the synthesis of tetrazole-containing buta-1,3-diynes: The total synthesis of 1,4-bis(2-(tert-butyl)-2H-tetrazol-5-yl)buta-1,3-diyne

An approach for the total synthesis of 1,4-bis(2-(tert-butyl)-2H-tetrazol-5-yl)buta-1,3-diyne was reported. Developed approach to the synthesis of 1,4-bis(2-(tert-butyl)-2H-tetrazol-5-yl)buta-1,3-diyne can be used for obtaining different 2,5-bis(tetrazol-5-yl)-disubstituted five-membered heterocycles (e.g. thiophenes, pyrroles, furans etc.), as well as tetrazole-containing monomers for the synthesis of new types of electroconductive and high energetic polymers.     

Development and validation of stability indicating RP-HPLC and HPTLC for determination of Niclosamide in bulk and in synthetic mixture

Two simple, specific, sensitive, accurate and precise stability indicating methods were described for quantitative determination of the anthelmintics drug Niclosamide. The first method was high performance liquid chromatographic with the use of a reversed phase hibar^R C-18 column (250 mm × 4.66 mm, 5 μm) and mobile phase of methanol: 1 mM ammonium phosphate buffer (85:15 v/v) at a flow rate of 1.2 mL/min. The retention time of drug was found to be 6.45 ± 0.02 min. Quantification of drug was achieved with diode array detection (DAD) at 332 nm. Linear calibration curve was obtained in concentration range 0.01–100 μg/mL with r² value of 0.999. The limit of detection and limit of quantification were found to be 0.048 μg/mL and 0.01 μg/ml respectively. The second method involved a high performance thin layer liquid chromatographic. Chromatographic separation was carried out with precoated silica gel G60 F254 aluminum sheets using toluene:ethyl acetate (7:3% v/v) as a mobile phase. Linearity of proposed method was found to be 200–700 ng/band at 332 nm with retention factor of 0.59 and r² value of 0.998. The limit of detection and limit of quantification were found to be 36.21 ng/band and 109.7 ng/band respectively. Both the developed methods were successfully validated as per International Conference on Harmonization guideline (ICH). Niclosamide was subjected to different stress conditions. The degraded product peaks were well resolved from the pure drug peak with significant difference in their retention time. Stress samples were successfully assayed by developed high performance liquid chromatographic and high performance thin layer liquid chromatographic method. Statistically analysis proves that there were no statistical significant differences between two developed methods.     

Construction of 1H-indazoles from ortho-aminobenzoximes by the Mitsunobu reaction

Recently, there has been an upsurge in the occurrence of the indazole motif in drug discovery. Accordingly, newer, milder and more efficient routes towards their synthesis have emerged in the literature. We recently reported the Mitsunobu-triggered cyclodehydration of salicylaldoximes to transient 1,2-benzisoxazoles, and salicylhydroxamic acids to their corresponding 3-hydroxybenzisoxazoles. We hypothesized subjecting ortho-aminobenzoximes to Mitsunobu conditions will likewise induce a cyclodehydration to deliver the corresponding 1H-indazoles. Indeed, secondary anilines afforded the predicted N¹-substituted 1H-indazoles, and primary anilines, after activation with a Boc group, furnished the N¹-Boc 1H-indazoles in good to excellent yields. This work further expands the chemical repertoire of the Mitsunobu reaction, representing its unprecedented use in the construction of the 1H-indazole nucleus.     

Catalytic wet air oxidation of phenol over ultrasound-assisted synthesized Ni/CeO2–ZrO2 nanocatalyst used in wastewater treatment

Non-noble metal Ni with different loadings was coated on precipitated CeO₂–ZrO₂ support by the sonochemistry method and examined for catalytic wet air oxidation of phenol. The structure of the nanocatalysts was determined by BET, FESEM, XRD, and FTIR analyses. The results showed non-uniform morphology of the nanocatalyst at lower Ni contents changed to homogenous morphology with spherical nano particles at higher Ni contents. While the size of NiO crystals remained constant with rising Ni content, the crystallinity of NiO significantly increased. If the crystallinity of NiO was 100% in 20% wt Ni/CeO₂–ZrO₂, the crystallinity of NiO in 5% wt Ni was found to be 41.13%. The average particle size in Ni(15%)/CeO₂–ZrO₂ was 77 nm in which 85.71% of particle diameters were less than 100 nm. Catalytic wet air oxidation of phenol with different Ni loadings indicated improvement of phenol destruction at higher amounts of active phase. Removal of phenol increased with increasing catalyst loading from 4 to 9.0 g/l but further increase to 10 g/l declined the catalyst reactivity.     

Chemically modified multiwalled carbon nanotubes as efficient and selective sorbent for separation and preconcentration of trace amount of Co(II), Cd(II), Pb(II), and Pd(II)

Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized by glutaric dihydrazide (GDH) and characterized with FT-IR technique. This new sorbent was used for enrichment and preconcentration of Co(II), Cd(II), Pb(II), and Pd(II) ions. The adsorption was achieved quantitatively on MWCNTs at pH 4.0, and then the retained metal ions on the adsorbent were eluted with 1.5 mol L^?1 HNO₃. The effects of analytical parameters including pH of the solution, eluent type, sample volume, and matrix ions were investigated for optimization of the presented procedure. The adsorption capacity of the adsorbent at optimum conditions was found to be 33.6, 29.2, 22.1, and 36.0 mg g^?1 for Co(II), Cd(II), Pb(II), and Pd(II), respectively. The LOD values of the method were 0.16, 0.19, 0.17, and 0.12 ng mL^?1 (3Sb, n = 10) for Co(II), Cd(II), Pb(II), and Pd(II), respectively. The RSDs values of the method were 0.75, 0.85, 1.16, and 1.30 ng mL^?1 for Co(II), Cd(II), Pb(II), and Pd(II), respectively. The method was applied for the determination of analytes in soil, well water, and wastewater samples with satisfactory results.     

Design,synthesis and evaluation of 2-(4-(substituted benzoyl)-1,4-diazepan-1-yl)-N-phenylacetamide derivatives as a new class of falcipain-2 inhibitors

The cysteine protease, falcipain-2 is an important drug target in human malaria parasite Plasmodium falciparum. A new series of 2-(4-(substituted benzoyl)-1,4-diazepan-1-yl)-N-phenylacetamide derivatives 5(a–t) were designed as per pharmacophoric requirements of falcipain-2 inhibitors using ligand-based approach. The target compounds were synthesized from the key intermediate, 2-(1,4-Diazepan-1-yl)-N-phenylacetamide, by coupling it with appropriate carboxylic acids using carbodiimide chemistry. Structural features of target compounds were characterized by spectral data (¹H NMR, and mass) and elemental analyses. The purity of the final compounds was confirmed by HPLC. The compounds were tested for their in vitro falcipain-2 inhibitor activity on recombinant falcipain-2 enzyme. Five compounds 5b, 5g, 5h, 5j, 5k showed good inhibitory activity (>60%), against falcipain-2 at 10 μM concentration, and fifteen compounds showed weak to moderate inhibitor activity. Compound 5g, the most potent compound from this series showed 72% inhibition at 10 μM concentrations.     

Isolation of phytosterols of Dalbergia ecastophyllum (L.) Taub. (Leguminosae) and modulation of antibiotic resistance by a possible membrane effect

Globally there are a larger number of strains of microorganisms resistant to multiple drugs mainly due to misuse and indiscriminate, resulting in increased morbidity, costs inherent benefits of health care, as well as mortality rates for infections. As a result of this a large number of researches have been conducted emphasizing the antimicrobial properties of plant products. In this study, the ethanol extract and hexane fraction of Dalbergia ecastophyllum (L.) Taub. (Leguminosae) have been used to evaluate the antibacterial and antifungal activity and for modulating the resistance of antimicrobials against bacterial strains of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans and fungal strains of Candida krusei, Candida tropicalis. The antibacterial and modulatory activity was determined by microdilution. Inhibition of the growth of bacteria and fungi tested extract was ?1024. The activity was enhanced when aminoglycosides were associated with sub-inhibitory concentrations of the ethanol extract and hexane fraction of Dalbergia ecastophyllum. Therefore, it is suggested that the ethanol extract and hexane fraction of Dalbergia ecastophyllum (L.) Taub. (Leguminosae) can be used as a source of natural products with a view to changing the resistance of these microorganisms to antimicrobials.     

Non-aqueous capillary electrophoretic enantiomer separations using the tetrabutylammonium salt of heptakis(2,3-O-diacetyl-6-O-sulfo)-cyclomaltoheptaose, a single-isomer sulfated beta-cyclodextrin highly-soluble in organic solvents

The tetrabutylammonium salt of heptakis(2,3-di-O-acetyl-6-O-sulfo)-cyclomaltoheptaose, a single-isomer sulfated beta-cyclodextrin that is adequately soluble in a number of protic and aprotic polar solvents was synthesized on the large scale and used for the capillary electrophoretic separation of the enantiomers of weak bases in acidic acetonitrile background electrolytes. The effective mobilities and separation selectivities observed for these analytes followed trends similar to those found with other single-isomer sulfated cyclodextrins in acidic methanol background electrolytes. Enantiomer separations obtained with the tetrabutylammonium and sodium salts of heptakis(2,3-di-O-acetyl-6-O-sulfo)-cyclomaltoheptaose were different indicating, for the first time, that selection of the counter ion of the single-isomer sulfated cyclodextrin is also of importance for the separation of enantiomers.     

Effect of clay surface on aldehyde-diol equilibrium

The effect of clay surface on the equilibrium between aldehyde and diol was examined by using 4-formyl-1-methylpyridin-1-ium chloride (MPy⁺) as a substrate. MPy⁺ exists as diol (DHMPy⁺) and aldehyde (FMPy⁺) in water and acetonitrile, respectively. It was turned out that FMPy⁺ was clearly observed in the presence of clay nanosheet even in water. This indicates that clay nanosheet surface acts as unique chemical reaction field, affecting the potential energy surface between FMPy⁺ and DHMPy⁺.     

Investigation of electrocoagulation reactor design parameters effect on the removal of cadmium from synthetic and phosphate industrial wastewater

This study investigates the effect of reactor design parameters on cadmium removal from industrial wastewater discharged by the Tunisian Chemical Group (TCG) to improve as much as possible efficiency and cost of electrocoagulation (EC) process. Based on an examination of the design parameters one by one, the best cadmium removal was achieved for an inter-electrode distance (d_ie) of 0.5 cm, monopolar connection mode, stirring speed of 300 rev min^?1, surface-area-to-volume ratio (S/V) of 13.6 m^?1, and an initial temperature of 50 °C. These operating conditions are allowed to achieve efficient removal in a relatively short operating time with the lowest energy consumption and cost possible. The present study proved that the parameters that have an effect on the operating cost are the electrode configuration, inter-electrode distance and S/V ratio. The energy consumption, the pH evolution, and the treatment cost were studied. The investigation of the effect of all the selected optimum EC design parameters together on the removal of cadmium from the TCG wastewater proved that the treatment was highly efficient; 100% of cadmium removal was reached in 5 min, with a very low power consumption (1.6 kW h m^?3) and very low cost (0.116 TND m^?3). Moreover, EC was found to be capable of removing cadmium as well as other pollutants at the same time from the case-study industrial wastewater. The investigation carried out in this work explores and proposes a very cost-effective treatment method to remove heavy metals from industrial wastewater if compared to results reported about cost of this treatment process through other widely used technologies such as coagulation (4.36 Tunisian National Dinar (TND) m^?3) and precipitation (9.96 TND m^?3) employed in previous studies.     

Palladium-catalyzed annulation of 2-(aryldiazenyl) aniline with dimethyl sulfoxide to access N-aryl-1H-benzo[d]imidazol-1-amine

A palladium-catalyzed annulation of 2-(aryldiazenyl) aniline and dimethyl sulfoxide was developed to access N-aryl-1H-benzo[d]imidazol-1-amine in moderate to good yields. Activated by 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) adduct (DABSO), DMSO served as a “CH” fragment during this procedure. It represents a facile pathway leading to benzimidazoles.     

A novel catalyst-free,eco-friendly,on water protocol for the synthesis of 2,3-dihydro-1H-perimidines

The first greenest methodology for the synthesis of 2,3-dihydro-1H-perimidines on water is described. 1,8-Diamino naphthalene was reacted with different types of aldehydes at room temperature to furnish the product in moderate to excellent yields in 30 min. A multi-gram scale reaction is also performed to ensure the scalability of the reaction.     

Introducing efficient palladium catalyzed cross coupling reaction of tertiary alcohols and aroyl chlorides for the synthesis of highly substituted esters

Esters are chemical compounds with many practical uses. The common type of esterification is called the Fischer esterification. Another one is by the action of acid chlorides on alcohols but not with tertiary alcohols. The stable carbenium ions formed from tertiary alcohols favor elimination and the byproduct, hydrogen chloride prevents ester formation. In this new report, palladium inserted ArCOPdCl species reacts with tertiary alcohols and cross-coupling under microwave heating, minimizes the formation of probable carbenium ion, and promotes successful production of highly substituted esters in good to high yields.     

Our expedition in the construction of fluorescent supramolecular metallacycles

During the past few years, the construction of fluorescent supramolecular metallocycles has attracted extensive attention due to their diverse applications such as sensing, photoelectric devices, and mimicking complicated natural photo-processes. In this review, we will discuss how we entered the field of fluorescent supramolecular metallacycles and what we investigated in this field. The preparation of various fluorescent supramolecular metallacycles and their applications in monitoring the dynamics of coordination-driven self-assembly, sensing, catalysts, and supramolecular gels will be summarized.     

TiO2/clay as a heterogeneous catalyst in photocatalytic/photochemical oxidation of anionic reactive blue 19

A TiO₂-coated Tunisian clay (TiO₂–clay) was synthesized by a typical impregnation method. The physicochemical characterization points to a successful impregnation of titania on the clay surface. The activity of this structured catalyst was studied in the photocatalytic/photochemical oxidation of anionic reactive blue 19 (RB 19). The effect of UVA and solar irradiation (UV-solar) was studied at room temperature. TiO₂–clay demonstrated an effective degradation of RB 19 under both types of irradiation. Moreover, in this study, the effects of various oxidants such as hydrogen peroxide (H₂O₂), potassium peroxodisulfate (K₂S₂O₈) and sodium carbonate (Na₂CO₃) were thoroughly investigated. H₂O₂ was a promising oxidant for promoting RB 19 degradation under UV_A. The kinetics of discoloration of RB 19 followed a pseudo-first-order rate law. We can remark that 20 min of UV irradiation was enough to achieve 100% discoloration of the aqueous solution. However, under UV–Vis, HPLC and chemical oxygen demand measurements indicated, that a longer reaction time (of around 45 min) was required for achieving the complete dye mineralization. The findings clearly demonstrated the applicability of this TiO₂/clay catalyst for the photocatalytic oxidation of RB 19.