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91.
Palladium-benzimidazolium salt catalyst systems have been studied for the Suzuki coupling. A different substitutent effect has been uncovered with respect to nitrogen substituents in the benzimidazolium salts from the palladium-imidazolium salt analogs. A practical and highly active palladium catalyst system, PdCl2/N,N′-dibenzylbenzimidazolium chloride 2, has been identified for the Suzuki coupling of aromatic halides with arylboronic acids. The coupling of a wide array of aromatic halides with arylboronic acids with the PdCl2-2 catalyst system gave good to excellent yields. The effective palladium loading could be as low as 0.0001 mol% and 0.01-0.1 mol% for iodide and bromide substrates, respectively. The coupling of unactivated aromatic chlorides with arylboronic acids also gave good results using Cs2CO3 as base with a 2 mol% palladium loading. The electronic factors from aromatic halides exert a significant influence on the Suzuki coupling catalyzed by the PdCl2-2 system while the electronic effect from the arylboronic counterparts is negligible. The aromatic halides with modest steric hindrance could also couple smoothly with phenylboronic acids using the PdCl2-2 catalyst system. 相似文献
92.
The acid-catalysed esterification of myristic acid with isopropanol was studied by using near-infrared spectroscopy (NIR) in combination with soft-modeling curve resolution (MCR) methodology with a view to establishing the effect of experimental variables on the reaction kinetics. The reaction was conducted at temperatures above the boiling point of the alcohol, with continuous addition of an isopropanol/water mixture to the reactor. Spectral and concentration profiles were determined by applying soft-modeling curve resolution methodology to a column-wise augmented data matrix containing the spectra for the pure components. MCR profiles were compared with reference values and found to depart from then by less than 3% as %RSE for concentrations and to exhibit correlation above 0.999 for spectra.The reaction kinetics as estimated from the concentration profiles was found to be pseudo-first-order. Also, the pseudo-first-order rate constant was found to depend on the flow-rate of the isopropanol/water mixture and its water content; although the constant decreased with increase in the proportion of water, a content of ca. 15% could be used without important retarding effects on the kinetics. The proposed NIR-MCR method allows the rate constant and the influence of the initial water content to be determined with a view to minimizing consumption of the raw materials and optimizing the experimental conditions. 相似文献
93.
Timo O. Harju 《Journal of Molecular Structure》1996,360(1-3):135-144
Ab initio Hartree-Fock calculations utilising STO-3G, 3-21G* and 6-31G* basis sets have been performed on three neutral and highly polar molecules, (diformylmethine)borondifluoride, (acetylacetonato)borondifluoride and (dibenzylmethine) borondifluoride. The calculated and experimental structures are well correlated when using the HF/3-21G* basis set, except for the structure parameters involving the boron atom. The HF/6-31G* basis set does not improve the accuracy in structure calculations. The conformational analysis is in agreement with the experimentally observed C2v symmetrical structures, where the boron atom is tetrahedrally coordinated. The calculations support a one-dimensional ground state barrier crossing reaction for (dibenzylmethine)borondifluoride, where the phenyl torsion is the most likely reaction coordinate. Both HF/6-31G* calculations and the second-order Møller-Plesset correction with the 3-21G* basis set suggest an activation energy of the ground state reaction of about 30 kJ mol−1. The ground state barrier crossing reaction kinetics is evaluated by the Kramers theory. The calculated ground state parameters relevant to the barrier crossing reaction are compared with the experimentally observed excited state values. 相似文献
94.
95.
Tenu R. Gentil S. Baudu S. Counioux J. J. 《Journal of Thermal Analysis and Calorimetry》1999,58(1):89-101
The binary system H2O—UO2(NO3)2 was studied by solubility measurements and constant heat flow thermal analysis. Temperature and composition of the eutectic transformation between ice and uranyl nitrate hexahydrate were accurately defined. A new hydrate with 24 molecules of water decomposes at –21°C according to the peritectoid reaction<UO2(NO3)2·24H2O> <UO2(NO3)2·6H2O> + 18<H2O>The quasi-ideal model was applied to the solid—liquid equilibria, using the following reaction hypothesis:((UO
2
2+
)) + 2((NO
3
–
))+ h((H2O)) ((UO2OH+aq)) + ((H3O+aq + 2((NO
3
–
aq))A complete calculation of the binary system was carried out with a global ionic hydration number h equal to 9 in the aqueous solutions. It allowed to the melting enthalpies of uranyl nitrate hydrates.
This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
96.
J. Ghazouani 《Thermochimica Acta》2005,432(1):10-19
Volumetric properties of several low acentric factor fluids (Ar, CH4, C2H6, Kr, N2, Ne, O2, Xe) as well as CO2 are modeled using the Bender equation of state. This equation is a linear function of 19 adjustable parameters, which are evaluated from properties data, using a linear numerical procedure. The validity of the EOS is tested by calculating the Joule-Thomson inversion curve. A simple model is in particular used to correlate the inversion properties predicted by the Bender equation, expressed in term of reduced pressure as a function of reduced temperatures ranging from 0.8 to 6. The simple correlation reproduces accurately the used data. We employ data on state behaviour ρ(P,T) of homogeneous fluid phases, vapour-liquid equilibrium, second virial coefficient and the coordinates of the critical point. 相似文献
97.
A novel solid-phase synthesis of 4-biaryl-piperidine-4-carboxamides has been developed using FDMP resin with a carboxamide as the anchor point. With this approach, three points of diversity were incorporated into a GPCR-directed scaffold. Final products were obtained in good purity and yield. 相似文献
98.
Yi-Chun Lai 《Tetrahedron》2005,61(40):9484-9489
Palladium-catalyzed Suzuki cross-coupling reactions employing Schiff-bases as ligands toward a series of substituted arylbromides and boronic acids were pursued. In the presence of a N,O-bidentate ligand, 2-[1-(2,4,6-trimethyl-phenylimino)-ethyl]-phenol 5, the catalytic reactions could be carried out efficiently at room temperature with a wide array of arylbromides, even with electronically deactivated arenes. A deprotonated 5, 5′, chelated palladium acetate complex, [5′Pd(II)(OAc)(solv)] 8, was proposed as a precursor of a genuine catalytically active species. 相似文献
99.
Pál Tapolcsányi Bert U.W Maes Katrien MonsieursGuy L.F Lemière Zsuzsanna RiedlGyörgy Hajós Bart Van den DriesscheRoger A Dommisse Péter Mátyus 《Tetrahedron》2003,59(31):5919-5926
Palladium-catalyzed intramolecular arylation of 2-benzyl-5-(2-bromophenyl)-4-phenylpyridazin-3(2H)-one yielded hitherto unknown 2-benzyldibenzo[f,h]phthalazin-1(2H)-one. The synthesis of this new tetracyclic pyridazinone from 2-benzyl-5-(2-aminophenyl)-4-phenylpyridazin-3(2H)-one via a Pschorr type reaction was also investigated. Similarly, the construction of 2-methyldibenzo[f,h]cinnolin-3(2H)-one from 2-methyl-5-(2-bromophenyl)-6-phenylpyridazin-3(2H)-one and 2-methyl-5-(2-aminophenyl)-6-phenylpyridazin-3(2H)-one is also reported. Removal of the N-benzyl protective group of 2-benzyl-dibenzo[f,h]phthalazin-1(2H)-one with AlCl3 yielded unsubstituted dibenzo[f,h]phthalazin-1(2H)-one. 相似文献
100.
一般增长曲线模型参数阵的BLU估计 总被引:4,自引:0,他引:4
考虑一般增长曲线模型:Y=X1BX2+εE(Vec(ε))=0V(Vec(ε))=σ2VIn(V0)本文对任一可估函数KBL给出了它的BLU估计(最佳线性无偏估计),并得到了方差σ2的一个无偏估计. 相似文献