Diboron-Assisted Copper-Catalyzed Z-Selective Semihydrogenation of Alkynes Using Ethanol as a Hydrogen Donor
摘要:
We herein describe a B(2)Pin(2)-assisted copper-catalyzed semihydrogenation of alkynes. A variety of alkenes were obtained in good to excellent yields with Z-selectivity under mild reaction conditions. Mechanistic studies indicated that a transfer hydrogenation process was involved and ethanol acted as both a solvent and a hydrogen donor in this reaction. The present protocol enabled convenient synthesis of deuterium-substituted Z-alkenes such as Z-Combretastain A4-d(2) in a high deuteration ratio by using readily available ethanol-d(1) as the deuterium source.
It Bu ( I t Bu = 1,3-di- tert -butylimidazol-2-ylidene) 代表了有机合成和催化中最重要和最通用的N-烷基 N-杂环卡宾。在此,我们报告了I t Oct (I t Octyl)、C 2 -对称、 I t Bu的高级同系物的合成、结构表征和催化活性。新的配体类别,包括饱和咪唑啉-2-亚基类似物,已与 MilliporeSigma 合作商业化:1 月929 298;SI t Oct , 929 492 使有机和无机合成领域的学术和工业研究人员能够广泛接触。我们证明用t -Oct替换t -Bu 侧链会导致迄今为止报道的N -烷基 N- 杂环卡宾的空间体积最高,同时保留 N- 脂肪族配体固有的电子特性,例如极强的 σ -对N-烷基N-杂环卡宾的反应性至关重要的贡献。咪唑鎓I t Oct和咪唑啉鎓SI t Oct的高效大规模合成介绍了卡宾前体。与 Au(
CuII-catalyzed regioselective borylation of alkynes and alkenes
作者:Shiwen Liu、Xiaojun Zeng、Bo Xu
DOI:10.1016/j.tetlet.2016.06.077
日期:2016.8
We developed a regioselective borylation of alkynes and alkenes protocol based on air-stable CuII/multi-dentate ligand system. Our catalytic system gives exclusive β-borylation products for most substrates in excellent chemical yields. We propose that multi-dentate electron poor nitrogen ligands can effectively discourage the formation of α-addition product through the steric hindrance and at same
我们开发了基于空气稳定的Cu II /多齿配体系统的炔烃和烯烃方案的区域选择性硼化。我们的催化系统以优异的化学收率为大多数底物提供独家的β-硼化产物。我们提出,多齿电子贫氮配体可以通过空间位阻有效地阻止α-加成产物的形成,同时保持良好的反应性。
Environmentally responsible, safe, and chemoselective catalytic hydrogenation of olefins: ppm level Pd catalysis in recyclable water at room temperature
作者:Balaram S. Takale、Ruchita R. Thakore、Eugene S. Gao、Fabrice Gallou、Bruce H. Lipshutz
DOI:10.1039/d0gc02087g
日期:——
Textbook catalytic hydrogenations are typically presented as reactions done in organic solvents and oftentimes under varying pressures of hydrogen using specialized equipment. Catalysts new and old are all used under similar conditions that no longer reflect the times. By definition, such reactions are both environmentally irresponsible and dangerous, especially at industrial scales. We now report
Basic CuCO<sub>3</sub>
/ligand as a new catalyst for 'on water' borylation of Michael acceptors, alkenes and alkynes: application to the efficient asymmetric synthesis of β-alcohol type sitagliptin side chain
作者:Gaj Stavber、Zdenko Časar
DOI:10.1002/aoc.2957
日期:2013.3
The efficient 'on water' β‐borylation using bis(pinacolato)diboron agent was achieved with a newly developed catalytic system based on basic copper carbonate and various ligands. The catalytic system was used for β‐borylation of various Michael acceptors, alkenes and alkynes. The presented methodology was successfully applied to the novel synthesis of β‐alcohol type sitagliptin side chain precursor
A Theoretically-Guided Optimization of a New Family of Modular P,S-Ligands for Iridium-Catalyzed Hydrogenation of Minimally Functionalized Olefins
作者:Jèssica Margalef、Xisco Caldentey、Erik A. Karlsson、Mercè Coll、Javier Mazuela、Oscar Pàmies、Montserrat Diéguez、Miquel A. Pericàs
DOI:10.1002/chem.201402978
日期:2014.9.15
thioether‐phosphite/phosphiniteligands has been evaluated in the asymmetric iridium‐catalyzedhydrogenation of minimallyfunctionalizedolefins. The modular ligand design has been shown to be crucial in finding highly selective catalysts for each substrate. A DFT study of the transition state responsible for the enantiocontrol in the Ir‐catalyzedhydrogenation is also described and used for further optimization
作者:Marvin Parasram、Viktor O. Iaroshenko、Vladimir Gevorgyan
DOI:10.1021/ja5104525
日期:2014.12.31
A palladium (Pd)-catalyzed endo-selectiveHeckreaction of iodomethylsilyl ethers of phenols and aliphatic alkenols has been developed. Mechanistic studies reveal that this silyl methyl Heckreaction operates via a hybrid Pd-radical process and that the silicon atom is crucial for the observed endo selectivity. The obtained allylic silyloxycycles were further oxidized into (Z)-alkenyldiols.