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41.
Ravi Vithalani Dikin S. Patel Chetan K. Modi Vaishali Sharma Prafulla K. Jha 《应用有机金属化学》2020,34(4):e5500
Graphene oxide (GO) supported transition metal complexes are apprised as sturdy and everlasting heterogeneous catalysts. GO surface was functionalized with 3-triethoxysilylpropylamine (TSPA) and this amino functionalized GO (A-f-GO) nanocomposite with vanadyl Schiff base complex (VO-f-GO) was prepared and to give credence of its potentiality, it was chosen for the selective epoxidation of styrene using environmentally benign 30% H2O2 to styrene oxide (SO). To evade the detrimental exposure of “inborn” water, a selective high boiling and potent hygroscopic solvent, ethylene glycol was chosen to make this transformation productively successful. With the assistance of theoretical studies, we have probed the effect of H2O2 on to structural properties, binding mechanism and electronic properties of the catalyst and substrate. Adsorption energy (Ead), energy band gap (Eg) and HOMO-LUMO were also calculated. Based on DFT calculations, resonance Raman and UV/Vis studies, we confirmed the formation of metal-peroxo species and propose the plausible catalytic pathway. The influence of the diverse experimental parameters, like substrate to oxidant mole ratio, catalyst concentration, type of solvents, solvent amount, time, temperature and oxidant were tested. A clear relationship was found between different reaction parameters like solvent amount, oxidant, catalyst concentration and temperature etc. and product distribution. This heterogeneous catalyst yielded styrene oxide as nearly the sole product (selectivity = 98.7%) with a conversion value of 99.2% in the oxidation of styrene with hydrogen peroxide in ethylene glycol. 相似文献
42.
The fluoroquinolone family member ciprofloxacin is well known for its drug design and coordinating ability towards metal ions. The coordination chemistry of this drug with metal ions of biological and pharmaceutical importance is of considerable interest. Novel Mn(III) mixed‐ligand complexes of ciprofloxacin with various bis‐pyrazolone‐based dinegative bidentate ligands were synthesized and characterized on the basis of their physical properties, magnetic susceptibility measurements, (FT‐IR and electronic) spectral studies. The FAB‐mass spectrum of [Mn(A9)(L)(H2O)2]·H2O [where H2A9 = 4,4′‐(p‐tolylmethylene)bis(3‐methyl‐1‐phenyl‐4,5‐dihydro‐1H‐pyrazol‐5‐ol) and HL = 1‐cyclopropyl‐6‐fluoro‐4‐oxo‐7‐(piperazin‐1‐yl)‐1,4‐dihydroquinoline‐3‐carboxylic acid] was determined. All the synthesized compounds were screened for their bioactivity. The mixed‐ligand complexes exhibited comparable activities against two Gram‐negative (Escherichia coli and Serratia marcescens) and two Gram‐positive (Staphylococcus aureus and Bacillus subtilis) microorganisms. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
43.
Yuelie Lu Tingjian Xiang Charles Bernard Liang Huang Aaron Siegmund Gary Guo Wanda Tormos Kevin Koch Laurence E. Burgess Prabha Ibrahim 《Tetrahedron》2006,62(50):11714-11723
A concise, scaleable synthesis of building block 10 for p38 kinase inhibitor B is described. The key step is the one-pot construction of 5-aryl-3-methyl-2-methylsulfanyl-6-pyridin-4-yl-3H-pyrimidin-4-one 4 from arylacetic acid ethyl ester 1. Subsequent hydrolysis of the thiomethyl group to the hydroxy group and chlorination provided the key intermediate, 2-chloro-3-methyl-6-pyridin-4-yl-5-aryl-3H-pyrimidin-4-one 10. This class of reactive building blocks enabled the rapid evaluation of a variety of side chains at the 2-position of the pyrimidinone in SAR studies of inhibitors of p38 MAP kinase. 相似文献
44.
45.
Jayapal P Sundararajan M Hillier IH Burton NA 《Physical chemistry chemical physics : PCCP》2006,8(35):4086-4094
We have explored possible mechanisms for the formation of the catalytically active Ni(a)-S state of the enzyme, nickel iron hydrogenase, from the Ni*(r) (ready) or Ni*(u) (unready) state, by reaction with H(2), using density functional theory calculations with the BP86 functional in conjunction with a DZVP basis set. We find that for the reaction of the ready state, which is taken to have an -OH bridge, the rate determining step is the cleavage of H(2) at the Ni(3+) centre with a barrier of approximately 15 kcal mol(-1). We take the unready state to have a -OOH bridge, and find that reaction with H(2) to form the Ni(r)-S state can proceed by two possible routes. One such path has a number of steps involving electron transfer, which is consistent with experiment, as is the calculated barrier of approximately 19 kcal mol(-1). The alternative pathway, with a lower barrier, may not be rate determining. Overall, our predictions give barriers in line with experiment, and allow details of the mechanism to be explored which are inaccessible from experiment. 相似文献
46.
Identification and characterization of vilazodone metabolites in rats and microsomes by ultrahigh‐performance liquid chromatography/quadrupole time‐of‐flight tandem mass spectrometry 下载免费PDF全文
47.
The behavior of the chelate, ferric dipivaloylmethide, Fe(DPM)3, in vinyl polymerization systems was investigated. The polymerization was found to be of free-radical nature. The rate of polymerization was proportional to the square root of the concentration of the chelate. The monomer exponent was close to 1.5 for the Fe(DPM)3-initiated polymerization of styrene and methyl methacrylate. The kinetic and transfer constants and activation energies for these systems have been evaluated. Spectral studies revealed the possibility of a complex formation between the chelate and the monomer. A kinetic scheme for the Fe(DPM)3-initiated polymerization is derived based on this initial complex formation. 相似文献
48.
Towards a total synthesis of the new anticancer agent mensacarcin: synthesis of the carbocyclic core
Tietze LF Stewart SG Polomska ME Modi A Zeeck A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(20):5233-5242
A synthesis of the carbocyclic core associated with the new anticancer agent mensacarcin (1) is reported. The strategy involves the synthesis of several novel highly substituted aromatic compounds, such as 12 and 23. The lithium derivative of 12 readily engages in a nucleophilic addition to benzaldehyde 4 to provide the diphenylcarbinol rac-15. The analogous benzyl ether rac-16 undergoes an intramolecular Heck reaction to provide the required tetrahydroanthracene rac-17, which can be transformed into the key tricyclic methyl ether rac-20. In a second approach, the lithium derivative of 21 is added to the hexasubstituted benzaldehyde 23 to give the diphenylcarbinol rac-35. Subsequent methylation to rac-36 followed by an intramolecular Heck reaction provides tricycle rac-37. Similarly, the oxidised compound 40 provides an electronically more suitable intramolecular Heck partner to afford compound 41. Further transformations of these substrates leads to rac-43, which incorporates the core structure of mensacarcin (1). 相似文献
49.
Maiti S Chatterji PR Nisha CK Manorama SV Aswal VK Goyal PS 《Journal of colloid and interface science》2001,240(2):630-635
Aggregation behavior in aqueous solution of a series of poly (ethylene glycol) (PEG)-based macromonomers with methacryloyl group as the only hydrophobic segment has been investigated using surface tension, steady-state and time-resolved fluorescence spectroscopy using pyrene as a probe, and small-angle neutron scattering techniques. The general formula of these macromonomers is CH2=C(CH3)–CO–O–Em–CH3, where E is the ethylene glycol unit and m=8 (ME8), 18 (ME18), 49 (ME49), and 120 (ME120). The results indicate that a macromonomer with 8 ethylene glycol units forms as an aggregate above a certain critical concentration, which can be defined as critical aggregation concentration. The observed high value of I1/I3 in pyrene emission spectra at the interface of these aggregates and the inability to scatter a neutron beam by these aggregates indicate that the hydrophobic cluster formed by this macromonomer is remarkably solvated. ME18 has a tendency to aggregate but others do not form any hydrophobic cluster. The homopolymerization behaviors of these macromonomers in an aqueous medium at 70°C are consistent with these possibi- lities. 相似文献
50.
Mahesh Sundararajan Gopalan Rajaraman Prabha Jayapal Venkatachalam Tamilmani Ponnambalam Venuvanalingam 《Journal of Molecular Structure》2005,730(1-3):155-160
Hydrolysis of carbonyl dichloride or phosgene (Cl2CO) in gas phase has been investigated at Hartree–Fock, density functional and ab initio levels of theory. The effects of basis sets on the energetics of the reaction have also been explored. Calculations reveal that initially carbonyl dichloride and water form a weak complex and this complex can react further in two ways. In Path 1, water adds on to carbonyl dichloride across carbonyl bond in a concerted fashion to give dichloromethane diol, and this diol decomposes to form chloro formic acid by syn-1,2-elimination of HCl and forms CO2 and HCl as final products. Path 2 is the concerted addition of water across carbon chlorine bond and elimination of HCl in a single step leading to the formation of chloro formic acid directly. This second path that skips the formation of dichloromethane diol is observed to be very low lying and hence is kinetically favored. Addition of second water molecule to the reacting system is found to catalyze the reaction by stabilizing the complex, intermediate and transition states and reduces the activation energy to 24.6 kcal mol−1 compared to 29.9 kcal mol−1 for a single water molecule. 相似文献