A team of 电子游戏软件 researchers has demonstrated an unprecedented catalytic approach that enables concurrent control of multiple convergences and selectivities in intermolecular amination of allylic carbon-hydrogen bonds in alkenes, 一类有价值但具有挑战性的有机反应, 该团队最近报道 化学性质.
This new catalytic process allows for selective transformation of the carbon-hydrogen bonds in common alkenes into value-added new alkenes bearing useful amine functionalities.
一个模型说明了一种前所未有的催化方法的各个方面, 是由电子游戏软件的化学家发明的, that enables concurrent control of multiple convergences and selectivities in intermolecular amination of allylic carbon-hydrogen bonds in alkenes, 一类有价值但具有挑战性的有机反应. (CC BY-NC-ND)
烯烃, hydrocarbons containing carbon–carbon double bonds in addition to carbon-hydrogen bonds, 在自然界中是否丰富且容易获得. They are commonly utilized for preparation of many other compounds with different structures and practical applications. 烯烃是催化领域的主力分子, attractive to researchers seeking new modes of chemical reactivities critical to scientific advancement.
Most catalytic methods have been developed to target the more reactive carbon–carbon double bonds in alkenes. A catalytic system that can selectively work on the less reactive carbon-hydrogen bond without touching the more reactive carbon-carbon double bond is much less common and its realization is considered as a triumph.
X. 彼得•张
The 电子游戏软件 team developed a catalytic approach to realize this challenging transformation through one-electron radical reaction carried out with a catalyst based on the earth-abundant and inexpensive metal cobalt, 第一作者、不列颠哥伦比亚省化学教授彼得·张说. 像这样, the catalytic process revealed by the team addresses important issues of sustainability in fine chemical manufacture and related applications in biology, 医学, 和材料.
Most metal-catalyzed processes rely on so-called "polar reactivity" wherein chemical reactions involve changes of two electrons at a time. Catalyzing two-electron polar reactions typically requires the use of rare and expensive metal ions, 张指出.
The team proposed a fundamentally new approach to better tame the unpredictable behavior of the highly reactive radicals associated with the classic Wohl-Ziegler reaction. The reaction involves the generation of delocalized allylic radicals as the key intermediates for functionalization of allylic carbon-hydrogen bonds in alkenes. 然而, the classic organic free radical reaction is difficult to control and typically generates a mixture of products, 张说.
以新兴的“金属催化”概念为指导," in which changes happen one electron at a time during the catalytic process, Zhang and his team developed a new cobalt-based catalytic system that takes advantage of the unique features of homolytic radical reaction. The cobalt catalyst center uses its unpaired electron to preferentially break the carbon-hydrogen bond but not the carbon-carbon bond to generate a delocalized allylic radical. 不同于经典的Wohl-Ziegler反应, this allylic radical is no longer “free” and is closely entangled by the catalyst, 张说. 结果是, it can form a new carbon-nitrogen bond to produce the desired amine product in a highly controlled and selective manner.
Through the employment of modularly-designed highly-symmetric chiral amidoporphyrins with a tunable pocket-like environment as the supporting ligand, cobalt-based metalloradical catalysis enabled the team to develop a new radical process for chemoselective intermolecular amination of allylic carbon-hydrogen bonds that provide a high degree of selectivity on several fronts in a single catalytic operation, 该团队报告说.
In addition to demonstrating the fundamental principles and unique opportunities of metalloradical catalysis in controlling homolytic radical reactions for molecular construction, the cobalt-catalyzed convergent carbon-hydrogen amination offers a practical and attractive methodology to synthesize valuable chiral α-tertiary amines from the direct use of an isomeric mixture of alkenes as the substrates. This new technology may find useful applications, especially in the pharmaceutical industry.
张说 the team was surprised to find out that the catalyst that works the best for the chemical transformation turns out to be the simplest member of ChenPhyrin catalyst family that the team has invented.
“前进, we hope to design the next generation of metalloradical catalysts that can function as powerful precision tools to remove a specific hydrogen atom at will from a complex molecule and then install a nitrogen-based functional group,张说。.
除了张, 电子游戏软件博士后潘旭, 电子游戏正规平台生谢晶晶, 和高级电子游戏正规平台员王多生共同撰写了 化学性质 报告题为 “Metalloradical approach for concurrent control in intermolecular radical allylic C−H amination.”
Ed Hayward |大学传播| 2023年2月