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71.
Santiago Conde Carlos Corral Jaime Lissavetzky 《Journal of heterocyclic chemistry》1985,22(2):301-304
A study on the oximation of a number of 2-acetylthiophenes in order to ascertain the validity of contradictory results previously described is reported. The fact that the steric hindrance is smaller in 2-acetylthiophenes unsubstituted at position-3 than in acetylbenzenes allows in these cases the formation of Z oximes, which even can predominate on the E oximes in the case of a + M substitution at position-5. In the paper is also shown that the E/Z ratio of 2-acetylthiophene oximes can be deduced from the 1H-nmr spectrum of the crude oxime mixture. 相似文献
72.
Wagner?M.?Teles Flávia?C.?Machado Carlos?A.?Montanari Carlos?A.?L.?FilgueirasEmail author Terence?C.?Jenkins 《Transition Metal Chemistry》2005,30(6):733-737
The mesoionic compound, 1,4,5-triazole-2-thiolate, is a versatile ligand, capable of binding metal centres in different ways. The present study shows how it reacts with the bridging platinum(II) complex μ-dichlorobis[(chlorotriethylphosphineplatinum(II)], [Pt2(PEt3)2Cl4], originating a bimetallic complex. Both the sulphur atom and nitrogen 3 behave as basic sites, coordinating different platinum centres. An interesting isomerization process, shown by 31P{1H} n.m.r. spectroscopy, occurs at the S-bonded platinum moiety, resulting in a fluxional behaviour of the complex. It is also shown to target CT-DNA with moderate binding affinity.To the memory of Dr. Wagner M. Teles (1971–2004). 相似文献
73.
Eduardo CortS Corts Carlos M. Alcocer Castrejn 《Journal of heterocyclic chemistry》1997,34(6):1809-1812
A series of twelve new 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodiazepine-2-thiones, which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3-dimercapto-1-(para-substituted phenyl)-2-propen-1-one with 3,4-diaminophenyl-R-phenyl ethers. The structure of all products was corroborated by ir, 1H-nmr, 13C-nmr and ms. 相似文献
74.
A computational strategy to model the amorphous phase of comblike polymers is presented. The strategy, denoted SuSi/CB (CB-configurational bias), combines the strength of an algorithm recently developed to generate reliable microstructures of dense amorphous polymers, which is based on a random search of energy minima, and configurational bias Monte Carlo method. The influence of different parameters used to define the characteristics of SuSi/CB on both the reliability of the generated structures and the computational effort has been examined in detail. Finally, we have modeled and characterized the supramolecular organization of poly(octadecyl acrylate) in the amorphous state. 相似文献
75.
Barluenga J Fernández MA Aznar F Valdés C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(8):2276-2283
A novel approach for the synthesis of the important indole ring is described. Indoles are obtained from o-bromoanilines and alkenyl halides in a Pd-catalyzed cascade process that involves an alkenyl amination followed by an intramolecular Heck reaction. The overall process represents the first example of the participation of alkenyl amination reactions in Pd-catalyzed cascade reactions. Initially, the relative reactivity of aryl and alkenyl bromides and chlorides towards Pd-catalyzed amination was investigated. Competition experiments were carried out in the presence of primary and secondary amines, and these revealed the reactivity order alkenyl bromides > aryl bromides > alkenyl chlorides > aryl chlorides, as well as very high chemoselectivity; the more reactive halide was always favored. Thereafter, optimized reaction conditions for the sequential alkenyl amination/Heck cyclization to give indoles were investigated with the model reaction of o-bromoaniline with alpha-bromostyrene. An extensive screening of ligands, bases, and reaction conditions revealed that the [Pd2(dba)3]/DavePhos, NaOtBu, toluene combination at 100 degrees C were the optimized reaction conditions to carry out the cascade process (dba=dibenzylideneacetone, DavePhos=2-dicyclohexylphosphino-2'-N,N-dimethylaminobiphenyl). The reaction proceeds with aryl, alkyl, and functionalized substitutents in both starting reactants. The cyclization was also studied with N-substituted o-bromoanilines (which would give rise to N-substituted indoles); however, in this case, indole formation occurred only with 1-substituted-2-bromoalkenes. Finally, the application of this methodology to o-chloroanilines required further optimization. Although the catalyst based on DavePhos failed to promote the cascade process, a catalytic combination based on [Pd2(dba)3]/X-Phos promoted the formation of the indole ring also from the less reactive chloroanilines. 相似文献
76.
João Paulo R.F. André Hugh D. Burrows Carlos F.G.C. Geraldes Maria Da Graça M. Miguel M.Helena S.F. Teixeira L.F. Vilas Boas 《Polyhedron》1996,15(24):4331-4340
Complexation of europium(III) with glyceryl-1- and -2-phosphates has been studied by metal ion luminescence, 1H and 13C NMR spectroscopy and potentiometry. From the luminescence and NMR studies, the formation of a 1:1 inner-sphere complex, in which the glyceryl phosphate is directly bound to the metal, is confirmed. Similar apparent binding constants at pH 2 were obtained by the three methods. Values obtained by NMR at pH 2 are 53 M−1 and 12 M−1 for glyceryl-1- and -2-phosphate, respectively. By comparison with literature data on related systems it is suggested that the ligands bind through the phosphate group. To obtain structural information from the NMR data, complexation has also been studied with the lanthanide ions Dy(III), Er(III) and Gd(III) using both chemical shift and relaxation data. From this, metal-proton distance ratios have been calculated. Comparison of 1H and 13C NMR spectral data in the presence of paramagnetic lanthanides suggests conformational equilibria in the solutions. From the potentiometric studies, global formation constants have been determined, and speciation diagrams obtained over the pH range 1.5pH7.0 for ligand/metal ratios of 1 and 30. Implications of these results on lanthanide induced fusion of phospholipid membranes are discussed. 相似文献
77.
The method is based on the highly sensitive reaction between cobalt and 4-(5-bromo-2-pyridylazo)-l,3-diaminobenzene. The cationic complex in slightly acidic solution is quantitatively extracted into chloroform as an ion pair with anthraquinone sulfonate; interfering ions are retained in the aqueous phase by selected masking agents. The cobalt complex is then rapidly back-extracted into 2.4 M HCl and measured at 573 nm (? = 1.16 × 105 l mol-1 cm-1). 相似文献
78.
Mercedes de Frutos Alejandro Cifuentes Jose Carlos Diez-Masa 《Journal of separation science》1997,20(1):29-33
The behavior of bovine whey proteins in Reversed-Phase High Performance Liquid Chromatography (RP-HPLC) systems has been investigated. The Linear Solvent Strength (LSS) model has been applied to the separation of these proteins studying how their retention time and band broadening change when different gradient parameters are modified. From our results it is deduced that the LSS model describes the behaviour of the whey proteins in RP-HPLC. Also, it seems that ts (the retention time for non-retained solutes) depends on the size of these proteins. The good fit observed between experimental data and the equations deduced from the LSS model allows the prediction of a gradient shape that permits a rapid analysis of the above mentioned proteins. 相似文献
79.
Carlos Vázquez-Vázquez M. Arturo López-Quintela 《Journal of solid state chemistry》2006,179(10):3229-3237
The synthesis of La1−xAxMnO3 (A=Ca, Sr, Ba) nanoparticles in nonaqueous solvents has been studied. For this solvothermal procedure benzyl alcohol and acetophenone were chosen as reaction media. After this treatment in mild conditions a precipitate was obtained, which, however, can be annealed to the crystalline perovskite structure. Our results show that acetophenone is more suited to obtain the clean pervoskite phase than benzyl alcohol. 相似文献
80.
The physical content of the three more natural models ofGL(4) gravity is analyzed, for the case of weak fields. The first model we deal with is the linearized version of Yang's onetensor-field gravity. It is shown that this is a scalar-tensor theory, with its scalar part contained in the symmetric tensorh
, instead of appearing explicitly, externally to the symmetric tensorh
, as happens in Brans-Dicke type of scalar-tensor theories. The second and the third linearized models, which can both be derived from the fourth-order action postulated by Yang, turn out to be two-tensor decoupled systems. In both cases one of the tensors is the symmetric weak metric gravity tensor field. The second tensor appearing in these two models, representing theGL(4)-gauge field, is either a linearized symmetric affinity (in the second model) or a linearized but nonsymmetric affinity (for the third model). It is shown that in these last two cases the affinity contains a helicity-3 propagating field. The connection is also given between the fourth-order system which determines the dynamical structure (for the last two models) of the metric tensor and the third-order Yang model of gravity. Owing to the presence of helicity-3 fields we show that it is better to regard Yang's action as an action for a two-tensor system instead of trying to recover from it a pure gravity (one-tensor-field) action. Finally, it is shown what is the dynamical structure of the second and third linearized two-tensor models which can be derived from Yang's action.On leave of absence from the Universidad Simón Bolívar. 相似文献