提出了使用一氧化碳作为直接还原剂将末端环氧化物和内部环氧化物脱氧成相应的烯烃。该反应由羰基钳-铱(I)络合物与路易斯酸助催化剂结合均匀催化,实现环氧化物底物的预活化,以及从γ-2-铱丁内酯中消除CO 2中间的。特别是末端烷基环氧化物在CO气氛下、苯或甲苯中、80-120℃下反应顺利,并且不会明显异构化为内烯烃。详细的研究揭示了环氧化物C−O键活化机制中底物依赖性变化,该变化发生在保留构型的氧化加成和导致构型反转的S N 2 反应之间。
A Ni(OAc)2‐catalyzed C−H coupling of 8‐aminoquinoline‐derived benzamides with epoxides has been developed. The reaction proceeds with concomitant removal of the 8‐aminoquinoline auxiliary to form the corresponding 3,4‐dihydroisocoumarins directly. Additionally, the nickel catalysis is stereospecific, and the cis‐ and trans‐epoxides are converted into the corresponding cis‐ and trans‐dihydroisocoumarins
Rhenium-Catalyzed Epoxide Deoxygenation: Scope and Limitations
作者:Kevin P. Gable、Eric C. Brown
DOI:10.1055/s-2003-42076
日期:——
Transfer of oxygen atoms from epoxides to triphenylphosphine is efficiently catalyzed by Tp′ReO3 [Tp′ = hydrido-tris-(3,5-dimethylpyrazolyl)borate] in benzene at 75-105 ºC. The reaction tolerates a wide variety of functional groups including ketones (conjugated or non-conjugated to the new double bond), esters, nitriles, ethers, silyl ethers and phthalimides. Relative rates vary with substitution pattern and electronics; in general, monosubstituted and 2,2-disubstituted epoxides react fastest, and cis-2,3-disubstituted systems react faster than trans. Electron-withdrawing substituents promote the reaction.
present the efficient isomerization of epoxides into methyl ketones with a novel pincer‐rhodium complex under very mild conditions. The catalyst system has an excellent functional group tolerance and a wide array of epoxides was tested. The corresponding methyl ketones were obtained in very high yields with excellent chemo‐ and regioselectivity. In addition, we investigated mechanistic details like the isomerization
Integrating Allyl Electrophiles into Nickel‐Catalyzed Conjunctive Cross‐Coupling
作者:Van T. Tran、Zi‐Qi Li、Timothy J. Gallagher、Joseph Derosa、Peng Liu、Keary M. Engle
DOI:10.1002/anie.201915454
日期:2020.4.27
offer exciting possibilities in organic synthesis but remains largely unknown. Herein, we report the use of allyl electrophiles in nickel-catalyzed conjunctive cross-coupling with a non-conjugated alkene and dimethylzinc. The transformation is enabled by weakly coordinating, monodentate aza-heterocycle directing groups that are useful building blocks in synthesis, including saccharin, pyridones, pyrazoles
Cooperative Multifunctional Organocatalysts for Ambient Conversion of Carbon Dioxide into Cyclic Carbonates
作者:Ning Liu、Ya-Fei Xie、Chuan Wang、Shi-Jun Li、Donghui Wei、Min Li、Bin Dai
DOI:10.1021/acscatal.8b01925
日期:2018.11.2
N-heterocyclic carbene precursor and a carboxyl group as proton transfer agent were synthesized and used as organocatalysts for the cycloaddition of epoxides with CO2. In this context, we have demonstrated the high activity of these one-component organocatalysts in the CO2 transformation to cyclic carbonates under ambient conditions (room temperature, 1 bar of CO2). The catalytic potential of these multifunctional
合成了一系列具有N杂环卡宾前体和羧基作为质子转移剂的钳型化合物,并将其用作有机催化剂,用于环氧化物与CO 2的环加成反应。在这种情况下,我们已经证明了这些单组分有机催化剂在环境条件(室温,1 bar CO 2)下从CO 2转化为环状碳酸酯的高活性。这些多功能有机催化剂在具有挑战性的内部环氧化物上的催化潜力特别值得一提,因为能够介导内部环氧化物与CO 2的环加成反应的有机催化剂在温和的条件下仍然稀缺。通过控制实验和DFT计算阐明了分子内的协同激活机制。