A highly efficient precatalytic system (XPhos-PdG2) for the Suzuki–Miyaura cross-coupling of 7-chloro-1H-pyrrolo[2,3-c]pyridine employing low catalyst loading

Molecular Diversity - An expedient catalytic method for the synthesis of diverse 7-(hetero) aryl-1H-pyrrolo[2,3-c]pyridine analogues via microwave-assisted Suzuki–Miyaura cross-coupling...     

Ni-Co-TiO2 nanocomposite coating prepared by pulse and pulse reversal methods using acetate bath

Ni-Co/nano TiO₂ (Ni-Co-TiO₂) composite coatings were prepared under pulse current and pulse reverse current methods using acetate bath. The microstructure and corrosion resistance of the coatings were characterized by means of XRD, SEM and EIS. Both the Ni-Co alloy and composite coatings exhibited single phase of Ni matrix with face centered cubic (fcc) crystal structure. The crystal orientation of the Ni-Co-TiO₂ composite coating was transformed from crystal face (2 0 0) to (1 1 1) compared with Ni-Co alloy coatings. The results showed that the microstructure and performances of the coatings were greatly affected by TiO₂ content on the deposits prepared by PC and PRC methods. The microhardness and corrosion resistance were enhanced in the optimum percentage of TiO₂ composite coatings. The PRC composite coatings were exhibited from compact surface, higher microhardness and good corrosion resistance compared with that of the PC composite coating.     

Synthesis and Characterization of Metabolites and Potential Impurities of Balsalazide Disodium,an Anti-Inflammatory Drug

Balsalazide disodium (Colazide®) is an oral prodrug of mesalamine (5-aminosalicylic acid) and possesses anti-inflammatory properties. During the process development for balsalazide disodium, we observed eight impurities, namely des-β-alanine balsalazide, balsalazide β-alanine, balsalazide 3-isomer, decarboxy balsalazide, bis-azo salicylic acid, biphenyl-azo salicylic acid, bis-azo diacid, and bis-azo triacid. The present work describes the synthesis and characterization of these impurities.     

Ultrasound Stimulated Nucleation and Growth of a Dye Assembly into Extended Gel Nanostructures

A squaraine dye functionalized with a bulky trialkoxy phenyl moiety through a flexible diamide linkage ( GA‐SQ ) capable of undergoing self‐assembly has been synthesized and fully characterized. Rapid cooling of a hot solution of GA‐SQ to 0 °C results in self‐assembled precipitates consisting of two types of nanostructures, rings and ill‐defined short fibers. The application of ultrasound modifies the conditions for the supersaturation‐mediated nucleation, generating only one kind of nuclei and prompting the formation of crystalline fibrous structures, inducing gelation of solvent molecules. The unique self‐assembling behavior of GA‐SQ under ultrasound stimulus has been investigated in detail by using absorption, emission, FT‐IR, XRD, SEM, AFM and TEM techniques. These studies reveal a nucleation growth mechanism of the self‐assembled material, an aspect rarely scrutinized in the area of sonication‐induced gelation. Furthermore, in order to probe the effects of nanoscale substrates on the sonication‐induced self‐assembly, a minuscule amount of single‐walled carbon nanotubes was added, which leads to acceleration of the self‐assembly through a heterogeneous nucleation process that ultimately affords a supramolecular gel with nanotape‐like morphology. This study demonstrates that self‐assembly of functional dyes can be judiciously manipulated by an external stimulus and can be further controlled by the addition of carbon nanotubes.     

Fortification of Ni–Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocomposite coatings prepared by pulse and direct current methods

Ni–Y₂O₃ nanocomposite coatings were prepared under direct current (DC) and pulse current (PC) using acetate bath. The microstructure and corrosion resistance of the coatings were characterized by means of XRD, SEM, AFM, and EIS. The results showed that the microstructure and performances of the coatings were greatly affected by Y₂O₃ content on the deposits prepared by DC and PC methods. The microhardness and corrosion resistance were enhanced in the optimum percentage of Y₂O₃ composite coatings. The PC composite coatings were exhibited compact surface, higher microhardness, and good corrosion resistance compared with that of the DC composite coatings.     

Selective methoxy ether cleavage of 2,6-dimethoxyphenol followed by a selective acylation

A Friedel-Crafts reaction of 2,6-dimethoxyphenol in the presence of aluminum chloride and propanoyl or butanoyl chlorid, respectively, lead, at elevated temperatures, to a selective cleavage of one of the methoxy groups followed by a selective acylation of the meta position with respect to the phenolic hydroxyl group. Under the same reaction conditions 2-methoxyphenol doesn't get demethylated; a mechanism to account for these findings is proposed. This reaction gives access to a variety of ortho-acylated catechols. Substituted catechols are widely used in supramolecular chemistry and are precursors of pesticides, flavors and fragrances. Additionally, catechol moieties are found in various natural products.     

Synthesis and characterization of sulfonated polymethylsiloxane polymer as template for crystal growth of CaCO3

The objective of this work was to synthesize a sulfonated polymethylsiloxane (S-PMS) by hydrosilylation and sulfonation reactions and to investigate their effect on the growth of CaCO₃ crystals using a gas diffusion method as a function of concentration, pH, and time. The result of IR and NMR shows good agreement with all proposed structures. Scanning electron microscopy images of CaCO₃ showed small well-defined calcite-forming short piles (ca 5 μm) and elongated calcite (ca 20 μm) crystals. The morphology of the resultant CaCO₃ crystals reflects the electrostatic interaction of sulfonate moieties and Ca²⁺ modulated by S-PMS adsorbed onto the CaCO₃ surface. X-ray diffraction confirmed the crystalline calcite polymorph. Energy dispersive spectroscopy of CaCO₃ crystals determined the presence of Si atoms from S-PMS. The use of PMS chemistry as an organic additive for the production of CaCO₃ particles is a viable approach for studying the biomineralization and could be useful for the design of novel materials with desirable shape and properties.     

Determination of rosuvastatin in rat plasma by HPLC: Validation and its application to pharmacokinetic studies

A specific, accurate, precise and reproducible high-performance liquid chromatography (HPLC) method was developed for the estimation of rosuvastatin (RST), a novel, synthetic and potent HMG-CoA inhibitor in rat plasma. The assay procedure involved simple liquid-liquid extraction of RST and internal standard (IS, ketoprofen) from a small plasma volume directly into acetonitrile. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Kromasil KR 100-5C18 column (4.6 x 250 mm, 5 microm). Mobile phase consisting of 0.05 m formic acid and acetonitrile (55:45, v/v) was used at a flow rate of 1.0 mL/min for the effective separation of RST and IS. The detection of the analyte peak was achieved by monitoring the eluate using a UV detector set at 240 nm. The ratio of peak area of analyte to IS was used for quantification of plasma samples. Nominal retention times of RST and IS were 8.6 and 12.5 min, respectively. The standard curve for RST was linear (r2 > 0.999) in the concentration range 0.02-10 microg/mL. Absolute recoveries of RST and IS were 85-110 and >100%, respectively, from rat plasma. The lower limit of quantification (LLOQ) of RST was 0.02 microg/mL. The inter- and intra-day precisions in the measurement of quality control (QC) samples, 0.02, 0.06, 1.6 and 8.0 microg/mL, were in the range 7.24-12.43% relative standard deviation (RSD) and 2.28-10.23% RSD, respectively. Accuracy in the measurement of QC samples was in the range 93.05-112.17% of the spiked nominal values. Both analyte and IS were stable in the battery of stability studies, viz. benchtop, autosampler and freeze-thaw cycles. RST was found to be stable for a period of 30 days on storage at -80 degrees C. The application of the assay to determine the pharmacokinetic disposition after a single oral dose to rats is described.     

Copper‐Catalyzed Oxidative C−H Bond Functionalization of N‐Allylbenzamide for Regioselective C−N and C−O Bond Formation

Copper‐catalyzed oxidative couplings of N‐allylbenzamides for C?N and C?O bond formations have been developed through C?H bond functionalization. To demonstrate the utility of this approach, it was applied to the synthesis of β‐aminoimides and imides. To the best of our knowledge, these are the first examples in which different classes of N‐containing compounds have been directly prepared from the readily available N‐allylbenzamides using an inexpensive catalyst/oxidant/base (CuSO₄/TBHP/Cs₂CO₃) system.     

Development and validation of a reversed-phase liquid chromatographic method with fluorescence detection for the study of Saquinavir pharmacokinetics in rat plasma

This research work aims to exploit the high selectivity and sensitivity of fluorescence detector to develop and validate a high performance liquid chromatography (HPLC) method having very small sampling volume, much better mass-sensitive detection limit and lower operating cost for the determination of Saquinavir (SQV), known to have low oral bioavailability, in rat plasma. Unlike the traditional methods that require at least 0.25 mL of plasma for each measurement, the present method requires only a 0.1 mL sample volume. This is very useful in reducing the blood collection from study rats, offering the possibility to make sufficient number of samples for pharmacokinetic study and minimizing the amount of blood-derived biological waste. After liquid-liquid extraction, the compounds were separated on a Vydac C₁₈ monomeric column (250 mm × 4.6 mm i.d. × 5 μm particle size) using a mobile phase composed of acetonitrile and potassium dihydrogen phosphate buffer (45:55, v/v). Fluorescence detection was performed at 237 nm (excitation) and 380 nm (emission). Validity of the method was studied and the method was found to be precise and accurate with a linearity range from 0.005 to 1.000 μg mL⁻¹ (r > 0.9980). The limit of detection (LOD) was found to be 0.001 μg mL⁻¹. The intra-day and inter-day precision studies showed good reproducibility with coefficients of variation (C.V.) less than 11.4%. The developed method was applied successfully to monitor the pharmacokinetic profile following oral administration of SQV to rats.