hydrazine monohydrochloride readily formed pyrazoline intermediates under mild conditions. Oxidation of pyrazolines, in situ, employing bromine afforded a wide variety of pyrazoles. The methodology offers a fast, and often chromatography-free protocol for the synthesis of 3,4,5-substituted pyrazoles in good to excellent yields. Alternatively, a more benign oxidation protocol affords 3,5-disubstituted or
Organocatalysis in Conjugate Amine Additions. Synthesis of β-Amino Acid Derivatives
作者:Mukund P. Sibi、Kennosuke Itoh
DOI:10.1021/ja071739c
日期:2007.7.1
Conjugateaddition of O-protected hydroxylamines to pyrazole-derived enoates proceeds with high efficiency and enantioselectivity when chiral thioureas are used as activators. A wide variety of substrates undergo conjugate amine addition providing access to enantioenriched β-aminoacidderivatives. Structural requirements for the optimal thiourea catalyst have been established, and the results suggest
Michael Cyclization of Polarized Systems: Synthesis and in vitro Anti-Diabetic Evaluation of Some Novel Pyrimidine, Pyridine, Pyrazole and Pyrazolo[3,4-b ]pyridine Derivatives
作者:Essam A. Soylem、Mohammed G. Assy、Ghania M. Morsi
DOI:10.5562/cca3122
日期:——
bromopyrazole 6a/6b pyrazole-1-carboxylate 8, pyridinylmethanone 9, nicotinonitrile 10, pyrazolopyridine 11a/11b, pyran-3-carbonitrile 12/13, chromenopyridine 14 and N-butyrylpyrazolyl-1-butanone 15 derivatives. The structures of the synthesized compounds were elucidated based on IR, NMR and mass spectral analyses. Group of the newly synthesized compounds were screened for their anti-diabetic activities
Structure and photoluminescence of silver(<scp>i</scp>) trinuclear halopyrazolato complexes
作者:Yui Morishima、David James Young、Kiyoshi Fujisawa
DOI:10.1039/c4dt01978d
日期:——
Luminescent silver(i) complexes of substituted halopyrazolate anions are either dimeric trinuclear or trinuclear structures held together with weak interactions.
Electronic structure and magnetic properties of a trigonal prismatic CuII6 cluster
作者:Ekaterina M. Zueva、Maria M. Petrova、Radovan Herchel、Zdeněk Trávníček、Raphael G. Raptis、Logesh Mathivathanan、John E. McGrady
DOI:10.1039/b907805c
日期:——
A combination of detailed magnetisation studies and electronic-structure analysis using broken-symmetry DFT is used to explore the electronic structure of a trigonal prismatic CuII6 cluster. The presence of six paramagnetic metal centres with S = 1/2 gives rise to a maximum multiplicity of S = 3 and a total of 31 broken-symmetry states with MS < 3. Computed differences in energy between the high-spin and broken-symmetry states are expressed in terms of the 15 distinct Heisenberg exchange coupling parameters, Jij, and the equations are solved by a least-squares fitting procedure. By inspection of the errors introduced by progressive symmetrisation of the Hamiltonian to reduce the number of independent Jij, we arrive at a minimal model containing only four distinct Jij (three intra- and one inter-triangular). The computed values then guide the fitting of the magnetisation data. The computed trends in Jij can only be reproduced when antisymmetric exchange is included in the model Hamiltonian. The use of this Hamiltonian provides a reasonable description of the magnetic behaviour at all temperatures and fields. If a simpler isotropic model Hamiltonian is used instead, the best fit values of Jij are compromised by the need to fit the low-temperature region where antisymmetric exchange dominates the shape of the curve.
研究人员结合详细的磁化研究和使用断裂对称 DFT 进行的电子结构分析,探索了三棱柱形 CuII6 团簇的电子结构。由于存在六个 S = 1/2 的顺磁金属中心,因此产生了 S = 3 的最大倍率和 MS < 3 的总共 31 个破对称态。计算出的高自旋态和非对称态之间的能量差异用 15 个不同的海森堡交换耦合参数 Jij 表示,并通过最小二乘拟合程序求解方程。通过对哈密顿逐步对称以减少独立 Jij 数量所带来的误差进行检验,我们得出了一个仅包含四个不同 Jij(三个三角形内和一个三角形间)的最小模型。计算出的数值将指导磁化数据的拟合。只有在模型哈密顿中加入反对称交换时,才能再现计算出的 Jij 趋势。使用该哈密顿模型可以合理地描述所有温度和磁场下的磁行为。如果使用更简单的各向同性模型哈密顿,由于需要拟合低温区域,Jij 的最佳拟合值就会受到影响,因为在该区域,反对称交换主导了曲线的形状。