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91.
The synthesis of new platinum bipy (bipy = 2,2′-bipyridyl) complexes containing phenoxide ligands is reported, together with kinetic studies of their oxidative addition reactions with MeI to produce phenoxo platinum(IV) complexes. Complexes of the form [(bipy)Pt(OC6H4-4-X)2] (X = OCH3, CH3, H, Br, Cl) are prepared by the reaction of the chloro complex [(bipy)PtCl2] with substituted phenols and KOH in a two phase system of water and chloroform in the presence of benzyl triphenylphosphonium chloride. Platinum(IV) complexes are formed by oxidative addition of MeI to the platinum(II) complexes obtained. The complexes are characterized by elemental analysis, UV-Vis, IR, mass spectrometry and 1H and 13C NMR spectroscopy.The reaction of methyl iodide with [(bipy)Pt(OC6H4-4-OMe)2] to give [(bipy)PtMe(I)(OC6H4-4-OMe)2] follows the rate law rate = k2[(bipy)Pt(OC6H4-4-OMe)2][MeI]. The values of k2 increase with increasing polarity of the solvent, suggesting a polar transition state for the reaction. 相似文献
92.
Erica Farnetti Author Vitae 《Inorganica chimica acta》2010,363(3):467-473
The ability of organoiridium derivatives of catalyzing oligomerization and polymerization of terminal alkynes is markedly influenced by the nature of non-participative ligands coordinated to the metal. The dimeric species [Ir(cod)Cl]2 and [Ir(cod)(OMe)]2 (cod = 1,5-cyclooctadiene) as well as the phosphine complexes HIr(cod)(PR3)2 (PR3 = PPh3, P(p-MeOC6H4)3, P(o-MeOC6H4)Ph2, PCyPh2) catalyze the polymerization reaction, whereas the diphosphine derivatives HIr(cod)(P-P) (P-P = Ph2P(CH2)nPPh2 (n = 1-4), o-C6H4(PPh2)2) promote the regioselective formation of 1,2,4-trisubstituted benzenes. On the other hand, the iridium complexes with nitrogen chelating ligands Ir(cod)(N-N)X and Ir(hd)(N-N)X (hd = 1,5-hexadiene; N-N = 1,10-phenanthroline and substituted derivatives; X = halogen) catalyze alkynes polymerization. In most cases one catalytic reaction predominates over the other possible routes, so that polymerization often takes place in the absence of oligomerization side reactions, and conversely cyclotrimerization is rarely accompanied by formation of either polyene or dimers. 相似文献
93.
The enantioselective epoxidation of 6-cyano-2,2-dimethylchromene (Chrom) catalysed by the Jacobsen catalyst, using sodium hypochlorite (NaOCl) as oxygen source, at room temperature, was performed in a series of 1,3-dialkylimidazolium and tetra-alkyl-dimethylguanidium based ionic liquids. All the room temperature ionic liquids (RTILs) could be used as reaction media for the enantioselective epoxidation of the alkene giving, generally, moderate to good epoxide yields and enantiomeric excesses (ee%).For the series of ionic liquids derived from the 1,3-dialkylimidazolium cation, it was observed some relationship between the RTILs physical properties and the catalytic reaction parameters, exemplified by linear correlations between (i) the ee% and the α Kamlet-Taft parameter (hydrogen bond acidity of the solvent) for CH2Cl2 and [C4mnim][BF4] ionic liquids (n = 1 or 2), and (ii) the ee% and the β Kamlet-Taft parameter (hydrogen bond basicity of the solvent) for CH2Cl2 and [C4mim][X] ionic liquids (X = PF6, NTf2 or BF4).All the RTILs could be reused in further catalytic cycles, with the exception of [C8mim][PF6]. The reutilisation of the Jacobsen catalyst for four times generally led to a decrease in the epoxide yield and to a slight decrease in the enantioselectivity. The recycling of the catalyst could be improved by imparting an ionic character to the complex through abstraction of the axially coordinated chloride anion (Cat 2). Other oxygen sources, such as iodosylbenzene, hydrogen peroxide and urea-hydrogen peroxide adduct, were also tested coupled with Jacobsen catalyst, but the best results were achieved with NaOCl. 相似文献
94.
The dinuclear V(V) complexes (VOL)2O (L = SAE (1), SAMP (2), SAP (3)) have been synthesized from VO(acac)2 and the corresponding tridentate ligands LH2 in methanol under reflux conditions and subsequent air oxidation in organic solvent. They have been characterized by IR and NMR spectroscopy, by thermogravimetric analysis, and by single crystal X-ray diffraction for 1 and 2. DFT calculations were carried out for a better understanding of the vibrational pattern, principally the V-O related vibrations. Complex [VO(SAP)]2O (3) catalyzes the epoxidation of cyclooctene by TBHP in water in the absence of any added solvent with good selectivity. 相似文献
95.
Martina Pressová Miloš Buděšínský Ivana Košiová Vladimír Kopecký Jr. Josef Cvačka Václav Kašička Ondřej Šimák Zdeněk Točík Ivan Rosenberg 《Biopolymers》2010,93(3):277-289
In an attempt to prepare a library of short oligoadenylate analogues featuring both the enzyme‐stable internucleotide linkage and the 5′‐O‐methylphosphonate moiety and thus obtain a pool of potential RNase L agonists/antagonists, we studied the spontaneous polycondensation of the adenosin‐5′‐O‐ylmethylphosphonic acid (pcA), an isopolar AMP analogue, and its imidazolide derivatives employing N,N′‐dicyclohexylcarbodiimide under nonaqueous conditions and uranyl ions under aqueous conditions, respectively. The RP LC–MS analyses of the reaction mixtures per se, and those obtained after the periodate treatment, along with analyses and separations by capillary zone electrophoresis, allowed us to characterize major linear and cyclic oligoadenylates obtained. The structure of selected compounds was supported, after their isolation, by NMR spectroscopy. Ab initio calculation of the model structures simulating the AMP‐imidazolide and pcA‐imidazolide offered the explanation why the latter compound exerted, in contrast to AMP‐imidazolide, a very low stability in aqueous solutions. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 277–289, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com 相似文献
96.
New enantiomerically pure macrocycles have been prepared by combining 1,10-phenanthroline 2,9-dicarboxylic acid and two alpha-amino-acids linked through spacers. Different diamine linkers have been employed in order to modify the dimensions and the properties of the macrocycles whose structures have been studied by 1H and 13C NMR spectroscopy. The ability of the (L)-valine containing macrocycles to bind metal ions and phenolic molecules has been investigated by 1H NMR experiments and Molecular Mechanics calculations. 相似文献
97.
The catalytic oxygenation of cyclohexane to cyclohexanol (-ol) and cyclohexanone (-one) using a series of di- and trivalent iron-picolinate complexes under GifIV conditions (10:1 v/v pyridine-acetic acid, zinc powder at room temperature under aerobic atmosphere) proceeds with turnover numbers [defined as (moles of oxygenated products)/(moles of catalyst)] of 161-184 and -one:-ol ratios of 4.2-4.7. The corresponding values for the binuclear picolinate complex [Fe2(μ-OMe)2(pic)4] (237 turnovers, -one:-ol ratio 7.2) are significantly higher. Iron complexes bearing functionalised pyridyl ligands exhibit turnover numbers and ketone selectivities of similar magnitude to, and in some cases higher than, the picolinate complexes. 相似文献
98.
Four new chiral pincer-complexes were prepared based on coupling of BINOL and TADDOL moieties with iodoresorcinol followed by oxidative addition of palladium(0). The X-ray analysis of complex 5a revealed that the BINOL rings form a well-defined chiral pocket around the palladium atom. This chiral environment can be further modified by γ-substitution of the BINOL rings. Preliminary studies for electrophilic allylation of sulfonimine 2 with allylstannane revealed that the presented chiral complexes are promising asymmetric catalysts for preparation of chiral homoallyl amines. The best result was achieved employing catalytic amounts of γ-Me BINOL complex 6 affording homoallyl amine 4 with 59% ee and 74% isolated yield. 相似文献
99.
Human nonpancreatic secreted phospholipase A2 (hnps PLA2) is considered to be an important drug target for antiinflammation therapy. We have established a new fluorescence assay by using 1-anilinonaphthalene-8-sulfonate (ANS) as an interfacial probe for hydrophobic environment detection. The fitted apparent k(cat)/K(m) of hnps PLA2 is 0.0181 +/- 0.0005 RFU/microMs. Tests on known synthesized inhibitor gave IC50 values similar to those from isotope-labeled assay. Because ANS is a commonly used probe for hydrophobic environment detection that needs no modification in the current assay, this strategy may be widely applicable for interfacial catalytic reactions. 相似文献
100.
Based on the X-ray crystal structures of 4-(4-chlorophenyl)imidazole (4-CPI)- and bifonazole (BIF)-bound P450 2B4, eight active site mutants at six positions were created in an N-terminal modified construct termed 2B4dH and characterized for enzyme inhibition and catalysis. I363A showed a >4-fold decrease in differential inhibition by BIF and 4-CPI (IC(50,BIF)/IC(50,4-CPI)). F296A, T302A, I363A, V367A, and V477A showed a 2-fold decreased k(cat) for 7-ethoxy-4-trifluoromethylcoumarin O-deethylation, whereas V367A and V477F showed an altered K(m). T302A, V367L, and V477A showed >4-fold decrease in total testosterone hydroxylation, whereas I363A, V367A, and V477F showed altered stereo- and regioselectivity. Interestingly, I363A showed a 150-fold enhanced k(cat)/K(m) with testosterone, and yielded a new metabolite. Furthermore, testosterone docking into three-dimensional models of selected mutants based on the 4-CPI-bound structure suggested a re-positioning of residues 363 and 477 to yield products. In conclusion, our results suggest that the 4-CPI-bound 2B4dH/H226Y crystal structure is an appropriate model for predicting enzyme catalysis. 相似文献