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排序方式: 共有516条查询结果,搜索用时 15 毫秒
511.
Farnaz Jafarpour Nafiseh Jalalimanesh Mina Barzegar Amiri Olia Asieh Otaredi Kashani 《Tetrahedron》2010,66(49):9508-9511
A simple and highly efficient protocol with mild reaction conditions has been developed that allows the smooth protiodecarboxylation of diversely functionalized coumarin-3-carboxylic acids. In the presence of catalytic amounts of Ag2CO3 and acetic acid, even un-activated coumarin-3-carboxylic acids were converted in good to excellent yields and with great preparative ease to the corresponding coumarin derivatives. 相似文献
512.
The effects of lattice vibration on the thermodynamics of nanosized coherent clusters in bcc-Fe consisting of vacancies and/or copper are investigated within the harmonic approximation. A combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by molecular dynamics is applied to obtain the most stable cluster configurations at T = 0 K. The most recent interatomic potential built within the framework of the embedded-atom method for the Fe-Cu system is used. The total free energy of pure bcc-Fe and fcc-Cu as well as the total formation free energy and the total binding free energy of the vacancy-copper clusters are determined for finite temperatures. Our results are compared with the available data from previous investigations performed using many-body interatomic potentials and first-principles methods. For further applications in rate theory and object kinetic Monte Carlo simulations, the vibrational effects evaluated in the present study are included in the previously developed analytical fitting formulae. 相似文献
513.
Quentin Lefebvre Mina Bocu Christophe Giorgiutti Thomas C. Fessard 《Helvetica chimica acta》2023,106(4):e202200189
Bicycloalkanes are well-known isosteres of alkynes and aromatic rings and their use in the field of medicinal chemistry and drug discovery has been on the rise in the past ten years. Herein, we report the modular and practical synthesis of bicycloalkane-containing fragments using nickel-photoredox catalysis. The comparison of their relevant physical-chemical properties with their aromatic counterparts shows a substantial improvement in LogP and aqueous solubility for bicyclo[1.1.1]pentane derivatives, but not for bicyclo[2.2.2]octane derivatives. 相似文献
514.
515.
Marina Lamberti Mina Mazzeo Daniela Pappalardo Adolfo Zambelli Claudio Pellecchia 《Macromolecular Symposia》2004,213(1):235-252
In the last few years several non-metallocene catalysts have been disclosed as efficient catalysts for the stereospecific polymerization of propene. In this paper we summarize some recent literature data and some new results concerning the stereochemical mechanism of propene polymerization promoted by late transition metal systems and group 4 metal bis(phenoxyimine) systems. NMR analysis of the fine structure of the polymers obtained, in some cases using isotopically enriched reagents, provides valuable information on the regiochemistry and stereochemistry of the polymerization. 相似文献
516.
Daniela Pappalardo Mina Mazzeo Claudio Pellecchia 《Macromolecular rapid communications》1997,18(12):1017-1023
Several nickel α-diimine compounds of the general formula (ArNC(R) C(R)NAr)NiX2 (Ar = 2,6-alkyl substituted Ph, R = H or CH3, X = Br or CH3) were tested in ethylene polymerization after activation with different co-catalysts, such as methylaluminoxane, Al(C2H5)2Cl or other aluminium alkyls, and ionizing reagents like B(C6F5)3, [CPh3][B(C6F5)4] or HBF4. The performances of the different catalytic systems were compared with reference to polymer productivity and structure. The degree of branching of the obtained polyethylenes was shown to depend not only on the ligand environment at the Ni centre but also on the type of co-catalyst. 相似文献