A new mechanism of FLPs catalyzed activation of heterocyclic C-H bond

The catalytic activation of inert C-H bond is one of the most basic and challenging steps in the construction of complex hydrocarbons, so it is known as the "Holy Grail" in the field of catalytic synthesis The traditional activation of C-H bond often depends on transition metal (especially noble metal) catalysts Recently, through the dual function strategy, FLPs have made a new breakthrough in the activation of C-H bond, expanding the new idea of C-H bond activation of blocked Lewis acid-base to nonmetal catalyst As a new type of non-metallic catalytic C-H bond activation method, the reaction mechanism of FLPs catalytic activation of C-H bond is of great significance to the following methodological exploration and catalyst design In this paper, the density functional theory (DFT) was used to study the activation of C-H bond by FLPs, and a new view on the catalytic mechanism was put forward (org Lett Doi: 10.1021 / ACS Orglett 8b00024) introduction to the research group of Professor Ke Zhuofeng of Sun Yat sen University The research group was established in September 2012 At present, there are 2 associate researchers, 3 postdoctoral students, 3 doctoral students and 3 master students in the research group Research direction of the research group: 1 Reaction mechanism and catalyst design; 2 New catalytic methods and synthesis; 3 Renewable energy, renewable resources and materials Prof Ke Zhuofeng, associate professor and doctoral supervisor of School of materials science and engineering, Sun Yat sen University Dr Sun Yat sen University / University of North Texas, researcher of fifc fellow, Keiichi Fukui, Kyoto University, Japan In 2012, Sun Yat sen University was introduced with the "one hundred talents plan" In 2015, it was awarded the outstanding youth of Natural Science in Guangdong Province and selected as the "top talent of one hundred million engineering youth" in Guangdong special support plan The research interest is mainly focused on the field of bionic bifunctional catalysis Through the combination of theory and experiment, the new strategies, mechanisms and methods of catalytic molecular transformation are studied, the rational precise design of catalyst is carried out, and its application in renewable energy and sustainable chemistry is explored More than 60 SCI papers have been published in j.am Chem SOC., angel Chem Int ed., chem SCI., ACS catalyst Leading research achievements: since Stephan et al Proposed the new concept of frustrated Lewis pairs (FLPs) in 2006 and successfully applied it to the activation of H 2, FLPs, as a new type of non-metallic bifunctional catalyst, has shown excellent performance in small molecule activation and catalytic conversion, which has aroused wide interest of researchers Recently, FLPs has made a new breakthrough in the catalytic activation of inert C-H bond, which provides a new idea for the non-metallic bifunctional catalytic C-H activation However, the mechanism and regulation of FLPs catalytic activation of C-H bond have yet to be elucidated Similar to the coordinated metallization deprotonization (CMD) mechanism catalyzed by transition metals, it is generally believed that FLPs are activated by C-H bond through the mechanism of cooperative heterocracking (see Fig 1b) The density functional theory was used to study the mechanism of FLPs catalyzing C-H bond, and another possible new mechanism, stepwise carbene mechanism, was proposed Figure 1 The synergistic mechanism of FLP catalytic C-H bond activation (source: org Lett.) the author first conducted a detailed literature survey, and found that the C-H bond activation of electron rich substrate is easier to carry out, so it can be inferred that C-H activation may go through electrophilic substitution process Inspired by the reported borane induced 1,2-H migration to caac-borane complex (see Fig 2a), the authors conclude that FLPs catalyzed heterocyclic C-H bond activation may also be initiated by Lewis acid (LA) center to 1,2-H migration to form carbene boron intermediate, and then Lewis base (LB) center assisted β - C-H deprotonation to achieve C-H bond activation (see Fig 2b) Figure 2 The hypothesis of fractional carbene mechanism of FLPs catalytic C-H bond activation (source: org Lett.) is different from the traditional synergistic C-H bond activation mechanism In the newly proposed fractional carbene mechanism, La and LB act respectively to promote C-H activation, and β - C will also participate in the process of H migration Therefore, the transition state of C-H activation in the two mechanisms is quite different The distance of LB may affect the recognition of catalyst and substrate in transition state To verify la Four kinds of FLPs composed of the same La, LB and different link structures were selected The synergistic mechanism and stepwise carbene mechanism were discussed systematically The relationship of LB distance The results of the calculation support the author's conclusion: when la When the LB distance is small, the synergistic mechanism is dominant, which is very consistent with the FLPs system reported in the literature With the increase of LB distance, the competition between cooperative mechanism and stepwise carbene mechanism begins to change, especially when la When the LB distance is large, the geometry of C-H bond between FLPs and substrate in the transition state of synergistic mechanism is poor, and the reaction tends to be carried out by step carbene mechanism Figure 3 La The mechanism of heterocyclic C-H bond activation catalyzed by LB distance regulated FLPs (origin: org Lett.) finally, the energy decomposition model of deformation energy binding energy was used to analyze la The intrinsic relationship between the LB distance effect and the activation mechanism of C-H is pointed out The matching of LB distance is the decisive factor for the reaction mechanism This work not only opens up a new understanding of the mechanism of C-H bond activation of FLPs, but also provides a new idea for the design and development of a more efficient FLPs catalyst system The first author of this paper is Dr Shao Youxiang The research was supported by the National Natural Science Foundation of China (21473261, 21673301) and Guangdong Provincial Outstanding Youth Fund (2015a030306027) Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeango app, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.