Steric effects of nucleophile-radical coupling reaction. Determination of rate constants for the reaction of aryl radicals with 2-naphthoxide anion
作者:Tomas C. Tempesti、Adriana B. Pierini、Maria T. Baumgartner
DOI:10.1039/b820374a
日期:——
The absolute rate constants for the reaction of different aryl radicals with 2-naphthoxide anion were determined using an indirect method, a competition of the coupling reaction with the H-atom abstraction. We here show that the radical-ambident nucleophile reactions are sensitive to steric hindrance. A lower reactivity is found for 2-anisyl radical with respect to 4-anisyl and for 2-methoxy-1-naphthyl
不同芳基与 2-萘氧基使用间接方法确定阴离子,即偶联反应与H原子抽象的竞争。我们在这里表明自由基-环境亲核反应对空间位阻敏感。发现较低的反应活性2-茴香基 激进的 4-茴香基 和为 2-甲氧基-1-萘基 激进的 1-萘基(k 2b < k 2a和k 2d < k 2c)。自由基中心的邻位取代降低了速率常数。反应性与通过理论计算确定的能垒一致。
Dynamic kinetic resolution of biaryl atropisomers by chiral dialkylaminopyridine catalysts
作者:Gaoyuan Ma、Chao Deng、Jun Deng、Mukund P. Sibi
DOI:10.1039/c8ob00384j
日期:——
The acylative dynamic kineticresolution (DKR) of configurationally unstable biaryl atropisomers is achieved by using newly developed chiral dialkylaminopyridine catalysts with fluxional chirality. Various types of biaryl substrates containing phenolic structures were subjected to the DKR to obtain a range of acylated biaryl products with enantiomeric ratios up to 90 : 10.
Dearomatization of Biaryls through Polarity Mismatched Radical Spirocyclization
作者:Carlos R. Azpilcueta‐Nicolas、Derek Meng、Simon Edelmann、Jean‐Philip Lumb
DOI:10.1002/anie.202215422
日期:2023.2
A redox-neutral dearomatization transforms biaryls into complex spirocycles commonly found in bioactive natural products. This polaritymismatchedradicalspirocyclization tolerates diverse functional groups and is applied in the regioselective synthesis of 2,4- and 2,5-cyclohexadienones. The first synthesis of denobilone A, a cytotoxic plant metabolite, showcases its utility to access underexplored
Axially Chiral 2-Hydroxybiaryls by Palladium-Catalyzed Enantioselective C–H Activation
作者:Pablo Losada、Laura Goicoechea、José Luis Mascareñas、Moisés Gulías
DOI:10.1021/acscatal.3c03867
日期:2023.11.3
strategy allows a directassembly of optically active, axially chiral 2-substituted-2′-hydroxybiaryls from readily available precursors and demonstrates that the native hydroxy unit of the substrates can work as an efficient directing group for the C–H activation. This represents a substantial advantage over other approaches that require the preinstallation of metal coordinating units. The simplicity
A mild robust generic protocol for the Suzuki reaction using an air stable catalyst
作者:Jonathan D. Moseley、Paul M. Murray、Edward R. Turp、Simon N.G. Tyler、Ross T. Burn
DOI:10.1016/j.tet.2012.05.030
日期:2012.7
A mild but robust procedure has been developed as a first pass generic protocol for the Suzuki-Miyaura reaction. The protocol employs an air stable palladium pre-catalyst at low loading (<= 1 mol %) in aqueous solvent mixtures at moderate temperature using potassium carbonate as base. Under these mild conditions, most aryl bromides will react with sterically and electronically demanding aryl boronic acids to give complete conversion to the product biphenyls in less than 1 h. Aryl chlorides are also fully converted in most cases either under identical conditions in 8-24 h, or in 2 h at elevated temperature. A further advantage of these mild conditions of moderate temperature, weak base and benign solvent is that sensitive functional groups and structural motifs are well tolerated. In addition, the lipophilic biphenyl products are readily isolated after a simple work-up procedure. These generic conditions are ideal for proof of transformation, and as the starting point for development and optimization of a specific process. The discovery and fine-tuning of this generic protocol will be presented, supported extensively by examples to illustrate its scope and utility. (C) 2012 Elsevier Ltd. All rights reserved.