Unusual dimerization of N-protected bromomethylindoles/benzyl bromide with arylmetal halides: generation of indolylmethyl/benzyl radical

A detailed study on the interaction of N-protected bromomethylindoles with various types of aryl/alkyl Grignard is reported. Full experimental details on the mechanism of the unusual dimerization reaction are presented.     

Development and validation of a sensitive LC-MS/MS method with electrospray ionization using multiple ions for quantitation of torcetrapib in hamster and dog plasma

A highly sensitive and specific LC-MS/MS method has been developed and validated for the estimation of torcetrapib (TTB) with 100 microL hamster/dog plasma using DRL-16126 as an internal standard (IS). The API-4000 Q Trap LC-MS/MS was operated under multiple-reaction monitoring mode using the electrospray ionization technique. The assay procedure involved extraction of TTB and IS from plasma with acetonitrile, which yielded consistent recoveries of 65.73 and 94.01% for TTB and 79.68 and 90.70% for IS in hamster and dog plasma, respectively. The total chromatographic run time was 3.0 min and the elution of TTB and IS occurred at approximately 2.25 and 2.20 min, respectively. The resolution of peaks was achieved with 0.01 m ammonium acetate:acetonitrile (15:85, v/v) at a flow rate of 0.40 mL/min on an Inertsil ODS-3 column. The method was proved to be accurate and precise at linearity range of 1.00-200 ng/mL with a correlation coefficient (r) of > or = 0.993. The method was rugged with 1.00 ng/mL as the lower limit of quantitation. TTB was stable in the battery of stability studies. The application of the assay to preclinical pharmacokinetic studies confirmed the utility of the assay to derive hamster/dog pharmacokinetic parameters.     

Ruthenium(II) carbonyl complexes of dehydroacetic acid thiosemicarbazone: Synthesis, structure, light emission and biological activity

The reaction of [RuHCl(CO)(B)(EPh₃)₂] (where E = As, B = AsPh₃; E = P, B = PPh₃, py, pip, or mor) and dehydroacetic acid thiosemicarbazone (abbreviated as H₂dhatsc where H₂ stands for the two dissociable protons) in benzene under reflux afford a series of new ruthenium(II) carbonyl complexes containing dehydroacetic acid thiosemicarbazone of general formula [Ru(dhatsc)(CO)(B)(EPh₃)] (where E = As, B = AsPh₃; E = P, B = PPh₃, py, pip or mor; dhatsc = dibasic tridentate dehydroacetic acid thiosemicarbazone). All the complexes have been characterized by elemental analyses, FT-IR, UV-Vis, and ¹H NMR spectral methods. The thiosemicarbazone of dehydroacetic acid behaves as dianionic tridentate O, N, S donor and coordinates to ruthenium via phenolic oxygen of dehydroacetic acid, the imine nitrogen of thiosemicarbazone and thiol sulfur. In chloroform solution, all the complexes exhibit metal-to-ligand charge transfer transitions (MLCT). The crystal structure of one of the complexes [Ru(dhatsc)(CO)(PPh₃)₂] (1) has been determined by single crystal X-ray diffraction which reveals the presence of a distorted octahedral geometry in the complexes. All the complexes exhibit an irreversible oxidation (Ru^III/Ru^II) in the range 0.76-0.89 V and an irreversible reduction (Ru^II/Ru^I) in the range −0.87 to −0.97 V. Further, the free ligand and its ruthenium complexes have been screened for their antibacterial and antifungal activities. The complexes show better activity in inhibiting the growth of bacteria Staphylococcus aureus and Escherichia coli and fungus Candida albicans and Aspergillus niger. These results made it desirable to delineate a comparison between free ligand and its ruthenium complexes.     

Copper nanoparticles in an ionic liquid: an efficient catalyst for the synthesis of bis-(4-hydroxy-2-oxothiazolyl)methanes

Copper nanoparticles were synthesized and characterized by TEM, XRD and UV-vis techniques. The copper nanoparticles in an ionic liquid were employed as a recyclable catalyst for the synthesis of bis-(4-hydroxy-2-oxothiazolyl)methanes in excellent yields and in short reaction times.     

Imidazolium-based polymer supported gadolinium triflate as a heterogeneous recyclable Lewis acid catalyst for Michael additions

A heterogeneous Lewis acid catalytic system has been developed by incorporating gadolinium triflate on to poly[styrene-co-(1-((4-vinylphenyl)methyl)-3-methylimidazolium) tetrafluoroborate] (1-Gd(OTf)₃), and the catalytic activity of this system has been examined for Michael additions of amines and thiols to α,β-unsaturated esters and acrylonitrile. The reactions proceed in moderate to excellent yields in the presence of catalytic system 1-Gd(OTf)₃. The catalytic system could be efficiently recycled and reused.     

Synthesis and characterization of ternary nanocomposites of TiO2/rGO/CdS as an efficient catalyst for photo-degradation of methyl orange

Novel ternary composite photocatalysts have been successfully prepared by TiO₂ nanofibers, reduced graphene oxide, and CdS nanoparticles (TiO₂/rGO/CdS) by using electrospinning technique with easy chemical methods. The structures and their properties are examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscope (FESEM). The structural characterization of the composite reveals that pure TiO₂ NFs and CdS NPs crystalline very well and the reduced graphene oxide is tightly composed with TiO₂ NFs and CdS Nps. The photodegradation of methyl orange (MO) under UV light illumination is significantly enhanced compared with that of bare materials. This ternary composite degrades methyl orange within 75 min. The enhanced photocatalytic degradation performance resulted from effective separation of e–h pairs with rGO sheets and also contributed for high rate degradation efficiency. This novel ternary composite has a potential application of wastewater purification and utilization for energy conversions.     

A facile synthesis of terminal arylacetylenes via Sonogashira coupling reactions catalyzed by MCM-41-supported mercapto palladium（0） complex

A variety of terminal arylacetylenes have been conveniently synthesized in good to high yields via Sonogashira coupling of aryl iodides with （trimethylsilyl）acetylene catalyzed by MCM-41-supported mercapto palladium（0） complex, followed by desilylation under mild conditions. This polymeric palladium catalyst can be reused many times without any decrease in activity.     

Unambiguous structural elucidation of base-modified purine nucleosides using NMR

A general and unambiguous approach has been developed for structural elucidation of modified purine nucleosides using NMR spectroscopy. Systematic assignment of proton and carbon signals of modified nucleosides was firmly established by COSY and the anomerism of the glycosidic linkage of synthetic nucleosides clearly elucidated by NOESY experiments. Characteristic properties of 15N-isotopic labelling at specific positions of nucleosides were also employed for structural studies. The reported approach is applicable to other modified nucleosides and nucleotides, as well as nucleobases.     

Dependence of enantioselectivity on the ligand/metal ratio in the asymmetric Michael addition of indole to benzylidene malonates: electronic influence of substrates

Simple bis(oxazoline) ligands, especially azabis(oxazolines), can promote the copper(II)-catalyzed Michael addition of indoles to benzylidene malonates with up to >99 % ee (ee=enantiomeric excess), provided that the ligand/metal ratio is tuned meticulously with particular regard to the electronic properties of the substrate. Despite a common paradigm followed in many asymmetric catalyses, an excess of chiral ligand is not always beneficial. In fact any excess of ligand has to be avoided to reach excellent enantioselectivities when electron-rich benzylidene malonates are used. On the contrary, malonates carrying an electron-withdrawing group require an excess of ligand for an optimum ee value. A correlation of optical yields versus the sigma(I) values of several para substituents shows a sigmoid trajectory. In the presence of an additive, such as triflate, the significance of the ligand/metal ratio vanishes and very good enantioselectivities are achieved at any rate--no matter whether electron-donating or withdrawing substituents are present.