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91.
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Arndt M Salih KS Fromm A Goossen LJ Menges F Niedner-Schatteburg G 《Journal of the American Chemical Society》2011,133(19):7428-7449
The ruthenium-catalyzed hydroamidation of terminal alkynes has evolved to become a broadly applicable tool for the synthesis of enamides and enimides. Depending on the catalyst system employed, the reaction leads chemo-, regio-, and stereoselectively to a single diastereoisomer. Herein, we present a comprehensive mechanistic study of the ruthenium-catalyzed hydroamidation of terminal alkynes, which includes deuterium-labeling, in situ IR, in situ NMR, and in situ ESI-MS experiments complemented by computational studies. The results support the involvement of ruthenium-hydride and ruthenium-vinylidene species as the key intermediates. They are best explained by a reaction pathway that consists of an oxidative addition of the amide, followed by insertion of a π-coordinated alkyne into a ruthenium-hydride bond, rearrangement to a vinylidene species, nucleophilic attack of the amide, and finally reductive elimination of the product. 相似文献
94.
The generation of a hidden Br?nsted acid as a true catalytic species in hydroalkoxylation reactions from metal precatalysts has been clarified in case studies. The mechanism of triflic acid (CF(3)SO(3)H or HOTf) generation starting either from AgOTf in 1,2-dichloroethane (DCE) or from a Cp*RuCl(2)/AgOTf/phosphane combination in toluene has been elucidated. The deliberate and controlled generation of HOTf from AgOTf and cocatalytic amounts of tert-butyl chloride in the cold or from AgOTf in DCE at elevated temperatures results in a hidden Br?nsted acid catalyst useful for mechanistic control experiments or for synthetic applications. 相似文献
95.
Rohr C Balbás Gambra M Gruber K Höhl C Malarek MS Scherer LJ Constable EC Franosch T Hermann BA 《Chemical communications (Cambridge, England)》2011,47(6):1800-1802
An interaction-site model can a priori predict molecular self-organisation on a new substrate in Monte Carlo simulations. This is experimentally confirmed with scanning tunnelling microscopy on Fréchet dendrons of a pentacontane template. Local and global ordering motifs, inclusion molecules and a rotated unit cell are correctly predicted. 相似文献
96.
97.
Markus Bursch Lukas Kunze Dr. Amol M. Vibhute Dr. Andreas Hansen Prof. Dr. Kana M. Sureshan Dr. Peter G. Jones Prof. Dr. Stefan Grimme Prof. Dr. Daniel B. Werz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(14):4627-4639
The noncovalent interactions between azides and oxygen-containing moieties are investigated through a computational study based on experimental findings. The targeted synthesis of organic compounds with close intramolecular azide–oxygen contacts yielded six new representatives, for which X-ray structures were determined. Two of those compounds were investigated with respect to their potential conformations in the gas phase and a possible significantly shorter azide–oxygen contact. Furthermore, a set of 44 high-quality, gas-phase computational model systems with intermolecular azide–pnictogen (N, P, As, Sb), –chalcogen (O, S, Se, Te), and –halogen (F, Cl, Br, I) contacts are compiled and investigated through semiempirical quantum mechanical methods, density functional approximations, and wave function theory. A local energy decomposition (LED) analysis is applied to study the nature of the noncovalent interaction. The special role of electrostatic and London dispersion interactions is discussed in detail. London dispersion is identified as a dominant factor of the azide–donor interaction with mean London dispersion energy-interaction energy ratios of 1.3. Electrostatic contributions enhance the azide–donor coordination motif. The association energies range from −1.00 to −5.5 kcal mol−1. 相似文献
98.
99.
E. O. Reed Dietz R. von Campbell und R. Lukas 《Fresenius' Journal of Analytical Chemistry》1919,58(4):159-161
Ohne Zusammenfassung 相似文献
100.
H. Hirata H. Komatsubara W. Blumund H. S. Rawdon R. Glockerund E. Kaupp F. Foerster G. L. Clark P. K. Frölich A. H. W. Aten L. M. Boerlage V. Kohlschütter A. Good F. Jakober D. J. Brown J. Heyrovsky F. S. Aumonier H. J. S. Sand J. E. Hackford H. S. Lukens A. Schleicher L. Toussaint A. Lassieur S. Wiechowski H. Rom A. Jilek J. Lukas Erich Müller R. Belasio E. Mellana P. Drossbach H. Ginsberg R. Geith 《Analytical and bioanalytical chemistry》1928,75(6):244-255