Transition-metal-catalyzed C-H bond activation - functionalization is one of the most efficient process for construction of new C-C or C-heteroatom bonds with high atom economy. In recent years, a lot of practical rhodium-catalyzed C-H bond activation – functionalization have been widely reported. At the same time, the theory and experimental study focusing on related reaction mechanisms have also been drawing close attention of the chemists at home and abroad.
Since 2012, the project team led by Professor Lan Yu has been carrying out systematic and in-depth exploration into the reaction mechanism of rhodium-catalyzed C-H bond activation – functionalization. The research content includes the rhodium-catalyzed C-H bond activation – Carbene insertion reaction (J. Am. Chem. Soc. 2015, 137, 1623.), C-H bond activation –alkyne insertion reaction (Chem. Eur. J. 2015, 21, 10131; J. Phys. Chem. A 2017, 121, 4496; ACS Catal. 2017, 7, 7296; J. Am. Chem. Soc. 2017, 139, 15724.), C-H bond activation – nitrene insertion reaction (ACS Catal. 2016, 6, 1971; Angew. Chem. Int. Ed. 2016, 55, 8696.), C-H bond activation – carbonyl insertion reaction (Organo llics 2016, 35, 1480.), C-H bond activation –olefin insertion reaction (ACS Catal. 2016, 6, 7744.), selective sp3 C-H bond activation oxidizing reaction (Chem. Eur. J. 2015, 21, 14937), transformation hydroformylation (J. Org. Chem. 2016, 81, 2320.) and aromatic hydrocarbon reaction (Chem. Eur. J. 2017, 23, 2690.). In those researches, the reaction mechanisms include 3 parts, including C-H bond cleavage involving rhodium, C-R bond transformation and regeneration of catalyst. The research carried out by the project team led by Professor Lan Yu focuses on the cleavage method of C-H bond, the chemical selectivity in the process of C-R transformation process and the change of oxidation state of rhodium in the catalyst cycle, so as to provide theoretical support for study of the reaction mechanism of the rhodium-catalyzed C-H bond activation – functionalization.
Based on the above systematic research work, the project team led by Professor Lan Yu was invited to write the review article titled Mechanism of Rhodium-Catalyzed C−H Functionalization: Advances in Theoretical Investigation by Professor Burrows, Cynthia J., the editor in chief of Accounts of Chemical Research of American Chemical Society, as a summary of related research work on the reaction mechanism of rhodium-catalyzed C-H bond activation – functionalization carried out by the project team. Recently, the paper was published on Accounts of Chemical Research, a top journal on chemistry. (Qi, X.; Li, Y.; Bai, R.; Lan, Y.* Acc. Chem. Res. 2017, 50, 2799-2808.(DOI:10.1021/acs.accounts.7b00400)) The first author of the paper is Doctor Qi Xiaotian graduated from Chongqing University. The author of the paper Li Yingzi, a doctoral candidate of Chongqing University, has made the same contribution to the paper as the first author. Another author of the paper is Doctor Bai Ruopeng of Chongqing University. Professor Lan Yu is the corresponding author of the paper and the communication address is Chongqing University.
The Accounts of Chemical Research is an influential journal in the chemistry research area (its factor of influence in 2016 was 20.27). It helps people to understand the latest progress of modern chemistry and is seemed as one of the top journals in the chemistry and chemical engineering area. The review articles published on Accounts of Chemical Research are description of the very outstanding systematic research written by the authors.
In the research carried out by the project team of Professor Lan Yu, the density functional theory calculation was used as the main research method. The elementary reaction path deformation - binding energy model was built up and used to study related issues of mechanism of homogeneous catalytic reaction, including the rhodium catalyzed HC functionalization reaction and the bond formation reaction involving free radicals. In the past 3 years starting from 2014, the project team led by Professor Lan Yu have published more than 80 scientific research papers (including received papers) on journals such as Accounts Chem. Res. (one solicited paper, IF = 20.27), J. Am. Chem. Soc. (6 papers, IF = 13.86), Angew. Chem. Int. Ed. (9 papers, IF = 11.99), Nature Commun. (four papers, IF = 12.12), Chem. Sci. (3 papers, IF = 8.67), ACS Catal. (5 papers, IF = 10.61), Sci. Adv. (1 paper), Science China: Chemistry (3 solicited papers) as the corresponding author. The research papers with Professor Lan Yu as the corresponding author have been cited by others for more than 1,000 times. All papers of Professor Lan Yu have been cited for more than 2,000 times. At present, the H factor of the project team led by Professor Lan Yu is 27 (data source: Researcher ID: A-8146-2016). Professor Lan Yu have directed two general projects supported by Natural Science Foundation of China and 1 youth project. In recognition of the above achievements, Professor Lan Yu was granted the “2016 Youth Chemistry Award of Chinese Chemical Society”. In addition, Professor Lan Yu was also granted the “2015 Physical Organic Chemistry Newcomer Award of Chinese Chemical Society”.
Abstract of the paper:
Transition- l-catalyzed cross-coupling has emerged as an effective strategy for chemical synthesis. Within this area, direct C–H bond transformation is one of the most efficient and environmentally friendly processes for the construction of new C–C or C–heteroatom bonds. Over the past decades, rhodium-catalyzed C–H functionalization has attracted considerable attention because of the versatility and wide use of rhodium catalysts in chemistry. A series of C–X (X = C, N, or O) bond formation reactions could be realized from corresponding C–H bonds using rhodium catalysts. Various experimental studies on rhodium-catalyzed C–H functionalization reactions have been reported and in tandem, mechanistic and computational studies have also progressed significantly.
Since 2012, our group has performed theoretical studies to reveal the mechanism of rhodium-catalyzed C–H functionalization reactions. We have studied the changes in the oxidation state of rhodium and compared the Rh(I)/Rh(III) catalytic cycle to the Rh(III)/Rh(V) catalytic cycle using density functional theory calculation. The development of advanced computational methods and improvements in computing power make theoretical calculation a powerful tool for the mechanistic study of rhodium chemistry. Computational study is able to not only provide mechanistic insights, but also explain the origin of regioselectivity, enantioselectivity, and stereoselectivity in rhodium-catalyzed C–H functionalization reactions.
This account summarizes our computational work on rhodium-catalyzed C–H functionalization reactions. The mechanistic study under discussion is divided into three main parts: C–H bond cleavage step, transformation of the C–Rh bond, and regeneration of the active catalyst. In the C–H bond cleavage step, computational results of four possible mechanisms, including concerted lation deprotonation (CMD), oxidative addition (OA), Friedel-Crafts-type (SEAr), and σ-complex assisted thesis (σ-CAM) are discussed. Subsequent transformation of the C–Rh bond, for example, via insertion of CO, olefin, alkyne, carbene, or nitrene constructs new C–C or C–heteroatom bonds. For the regeneration of the active catalyst, reductive elimination of a high-valent rhodium complex and protonation of the C–Rh bond are emphasized as potential mechanism candidates. In addition to detailing the reaction pathway, the regioselectivity and diastereoselectivity of rhodium-catalyzed C–H functionalization reactions are also commented upon in this account. The origin of the selectivity is clarified through theoretical analysis. Furthermore, we summarize and compare the changes in the oxidation state of rhodium along the complete reaction pathway. The work described in this account demonstrates that rhodium catalysis might proceed via Rh(I)/Rh(III), Rh(II)/Rh(IV), Rh(III)/Rh(V), or non-redox-Rh(III) catalytic cycles.