Synthesis and metathesis activity of ruthenium dimethylvinyl carbene complexes

Two new dimethylvinyl carbene complexes, RuCl₂(SIMes)(PPh₃)CHCHC(CH₃)₂ and RuCl₂(SIMes)(3BP)₂CHCHC(CH₃)₂, were synthesized from RuCl₂(PCp₃)₂CHCHC(CH₃)₂. Complex RuCl₂(SIMes)(3BP)₂CHCHC(CH₃)₂ does not suffer from the problem of incomplete initiation that has been observed for the other dimethylvinyl carbene complexes, as witnessed by complete and rapid reaction with ethyl vinyl ether. Acyclic diene metathesis (ADMET) polymerization of 1,9‐decadiene with these complexes was found to give polymers with chemical and thermal properties similar to those obtained with Schrock's molybdenum catalyst. These complexes are also catalysts for ring‐opening metathesis polymerization. The parent complex RuCl₂(SIMes)(PCp₃)CHCHC(CH₃)₂ was found to give polyoctenamer with high initial heats of fusion, suggesting a dependence of the “as formed” crystallinity of the polymer on the rate of the ROMP reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6134–6145, 2005     

On the magnetic non-equivalence of methylene protons in some propane derivatives, and its variation with solvent and temperature

The magnetic non-equivalence, δ ab, of methylene protons in 1,2-disubstituted and 1,2,3-trisubstituted propanes (same substituent) shows a marked dependence on solvent and temperature that allows a correlation with conformational equilibrium. Results indicate that symmetry is a necessary, but not a sufficient, condition for observation of δ ab. Factors that affect rotamer population such as medium, temperature, and nature of substituents, contribute substantially to the magnitude of δ ab.     

Polymeric alkenoxy amino acid surfactants: II. Chiral separations of beta-blockers with multiple stereogenic centers

Two amino acid-based (leucine and isoleucine) alkenoxy micelle polymers were employed in this study for the separation of multichiral center-bearing beta-blockers, nadolol and labetalol. These polymers include polysodium N-undecenoxy carbonyl-L-leucinate (poly-L-SUCL) and polysodium N-undecenoxy carbonyl-L-isoleucinate (poly-L-SUCIL). Detailed synthesis and characterization were reported in our previous paper [26]. It was found that poly-L-SUCIL gives better chiral separation than poly-L-SUCL for both nadolol and labetalol isomers. The use of 50-100 mM poly-L-SUCIL as a single chiral selector provided separation of four and three isomers of labetalol and nadolol, respectively. Further optimization in separation of both enantiomeric pairs of nadolol and labetalol was achieved by evaluation of type and concentration of organic solvents, capillary temperature as well type and concentration of cyclodextrins. A synergistic approach, using a combination of poly-L-SUCIL and sulfated beta-CD (S-beta-CD) was evaluated and it showed dramatic separation for enantiomeric pairs of nadolol. On the other hand for labetalol enantiomers, separation was slightly decreased or remain unaffected using the dual chiral selector system. Finally, simultaneous separation of both nadolol and labetalol enantiomers was achieved in a single run using 25 mM poly-L-SUCIL and 5% w/v of S-beta-CD in less then 35 min highlighting the importance of high-throughput chiral analysis.     

Sensitive Voltammetric Method for Rapid Determination of Sarcosine as a New Biomarker for Prostate Cancer Using a TiO2 Nanoparticle/Ionic Liquid Modified Carbon Paste Electrode

Russian Journal of Electrochemistry - Sarcosine has been identified as a key metabolite marker for monitoring and early diagnosis of metastatic prostate cancer (PCa), and it is detectable in the...     

Fe3O4@Propylsilane@Histidine[HSO4‐] magnetic nanocatalysts: Synthesis,characterization and catalytic application for highly efficient synthesis of xanthene derivatives

The surface of Fe₃O₄ magnetic nanoparticles (MNPs) was modified by chloropropylsilane and histidine. The imidazole group of prepared Fe₃O₄@Propylsilane@Histidine MNPs converted to imidazolium hydrogen sulfate group and Fe₃O₄@Propylsilane@Histidine [HSO₄^‐] as a novel environmentally friendly ionic liquid/ magnetite nanoparticle was prepared, successfully. FT‐IR, XRD, SEM and TEM instruments was used to identifiy the histidine ionic liquids/magnetite nanoparticles (HILMNPs). The catalytic activity of synthesized HILMNPs was appraised for the synthesis of 9‐aryl‐1,8‐dioxooctahydroxanthene and spiro[indoline‐3,9′‐xanthene]trione derivatives. The activity of HILMNPs was much better than the other reported heterogeneous and homogeneous catalysts. Furthermore, the prepared catalyst could be separated from the reaction mixture and reused four times without any significant loss in its activity.     

Experimental Investigation of the Effects of Different Parameters on the Rate of Asphaltene Deposition in Laminar Flow and Its Prediction Using Heat Transfer Approach

In this study, asphaltene deposition from crude oil on the pipe surface has been studied experimentally using a novel designed test loop. Washing technique is used to quantitatively measure the rate of asphaltene deposition during laminar flow in the steel pipe. The effects of oil velocity, asphaltene content, and surface temperature on the thickness of asphaltene deposition are investigated. The results show that the asphaltene deposition rate increases with increasing surface temperature, results in asphaltene content reduction of the flowing crude oil. As the oil velocity increases, less deposition was noticed on the surface of the pipe. Besides, thermal approach was applied to the experimental procedure which shows good agreements between the predicted thickness and the measured value from the test loop.     

Synthesis,characterization, X-ray diffraction,antimicrobial and in vitro cytotoxicity studies of 7a-Aza-B-homostigmast-5-eno [7a,7-d] tetrazole

The synthesis, spectral characterization, crystal structure and antimicrobial activity of the novel synthetic molecule 7a-Aza-B-homostigmast-5-eno [7a,7-d] tetrazole, C₂₉H₄₈N₄ has been reported. The structure has also been determined by X-ray diffraction technique using direct method and was refined on F² by the full-matrix least-squares. Crystals are orthorhombic and their space group is P212121, with a = 7.230(3), b = 31.451(13), c = 11.974(5) (Å), α = β = γ = 90°. It can be conveniently obtained by the reaction of 7-Oxostigmast-5-ene with hydrazoic acid. The molecule has also been screened for its possible in vitro antimicrobial activity against Staphylococcus aureus, Streptococcus mutans, Streptococcus pyogenes, Staphylococcus epidermidis, Bacillus cereus, Corynebacterium xerosis, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Pseudomonas aeruginosa (MTCC 424). Minimum inhibitory concentration (MIC) of the synthesized compound has also been evaluated. The highest activity is observed against C. xerosi and P. vulgaris. Moreover, the compound has also been screened for its in vitro cytotoxicity against human colon carcinoma cell line, HCT116 and human liver hepatocellular carcinoma cell line, HepG2, using doxorubicin as standard. On the basis of its IC₅₀ values, 7a-Aza-B-homostigmast-5-eno [7a,7-d] tetrazole was found to inhibit the cancer cells effectively.