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A Convenient Synthesis of N‐Aryl Benzamides by Rhodium‐Catalyzed ortho‐Amidation and Decarboxylation of Benzoic Acids 下载免费PDF全文
Dr. Xian‐Ying Shi Ke‐Yan Liu Juan Fan Xue‐Fen Dong Prof. Dr. Jun‐Fa Wei Prof. Dr. Chao‐Jun Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1900-1903
The rhodium‐catalyzed amidation of substituted benzoic acids with isocyanates by directed C?H functionalization followed by decarboxylation to afford the corresponding N‐aryl benzamides is demonstrated, in which the carboxylate serves as a unique, removable directing group. Notably, less common meta‐substituted N‐aryl benzamides are generated readily from more accessible para‐ or ortho‐substituted groups by employing this strategy. 相似文献
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Formation of Long,Multicenter π‐[TCNE]22− Dimers in Solution: Solvation and Stability Assessed through Molecular Dynamics Simulations
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Dr. Marçal Capdevila‐Cortada Dr. Jordi Ribas‐Arino Dr. Alain Chaumont Prof. Georges Wipff Prof. Juan J. Novoa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):17037-17046
Purely organic radical ions dimerize in solution at low temperature, forming long, multicenter bonds, despite the metastability of the isolated dimers. Here, we present the first computational study of these π‐dimers in solution, with explicit consideration of solvent molecules and finite temperature effects. By means of force‐field and ab initio molecular dynamics and free energy simulations, the structure and stability of π‐[TCNE]22? (TCNE=tetracyanoethylene) dimers in dichloromethane have been evaluated. Although the dimers dissociate at room temperature, they are stable at 175 K and their structure is similar to the one in the solid state, with a cofacial arrangement of the radicals at an interplanar separation of approximately 3.0 Å. The π‐[TCNE]22? dimers form dissociated ion pairs with the NBu4+ counterions, and their first solvation shell comprises approximately 20 CH2Cl2 molecules. Among them, the eight molecules distributed along the equatorial plane of the dimer play a key role in stabilizing the dimer through bridging C?H???N contacts. The calculated free energy of dimerization of TCNE . ? in solution at 175 K is ?5.5 kcal mol?1. These results provide the first quantitative model describing the pairing of radical ions in solution, and demonstrate the key role of solvation forces on the dimerization process. 相似文献
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Dr. Jingjun Hao Prof. Arnold L. Rheingold Marzieh Kavand Dr. Kipp J. van Schooten Prof. Christoph Boehme Dr. Marçal Capdevila‐Cortada Prof. Juan J. Novoa Eva Wöss Prof. Günther Knör Prof. Joel S. Miller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(35):12312-12315
The reaction of 2,3,5,6‐tetracyanopyridine (TCNPy) and Cr(C6H6)2 forms diamagnetic σ‐[TCNPy]22? possessing a 1.572(3) Å intrafragment sp3–sp3 bond. This is in contrast to the structurally related 1,2,4,5‐tetracyanobenzene and 1,2,4,5‐tetracyanopyrazine that form π‐dimer dianions possessing long, multicenter bonds. 相似文献
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Juan M. Muñoz-Ocaña Ainouna Bouziane Farzeen Sakina Richard T. Baker Ana B. Hungría Jose J. Calvino Antonio M. Rodríguez-Chía Miguel López-Haro 《Particle & Particle Systems Characterization》2020,37(6):2000070
A novel procedure to optimize the 3D morphological characterization of nanomaterials by means of high angle annular dark field scanning-transmission electron tomography is reported and is successfully applied to the analysis of a metal- and halogen-free ordered mesoporous carbon material. The new method is based on a selection of the two parameters (μ and β) which are key in the reconstruction of tomographic series by means of total variation minimization (TVM). The parameter-selected TVM reconstructions obtained using this approach clearly reveal the porous structure of the carbon-based material as consisting of a network of parallel, straight channels of ≈6 nm diameter ordered in a honeycomb-type arrangement. Such an unusual structure cannot be retrieved from a TVM 3D reconstruction using default reconstruction values. Moreover, segmentation and further quantification of the optimized 3D tomographic reconstruction provide values for different textural parameters, such as pore size distribution and specific pore volume that match very closely with those determined by macroscopic physisorption techniques. The approach developed can be extended to other reconstruction models in which the final result is influenced by parameter choice. 相似文献
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Mathematical Programming - We propose a new method for simplifying semidefinite programs (SDP) inspired by symmetry reduction. Specifically, we show if an orthogonal projection map satisfies... 相似文献