title: The Mechanism of N-O Bond Cleavage in Rhodium-Catalyzed C-H Bond Functionalization of Quinoline N-oxides with Alkynes: A Computational Study.
abstract: Metal-catalyzed C-H activation not only offers important strategies to construct new bonds, it also allows the merge of important research areas. When quinoline N-oxide is used as an arene source in C-H activation studies, the N-O bond can act as a directing group as well as an O-atom donor. The newly reported density functional theory method, M11L, has been used to elucidate the mechanistic details of the coupling between quinoline N-O bond and alkynes, which results in C-H activation and O-atom transfer. The computational results indicated that the most favorable pathway involves an electrophilic deprotonation, an insertion of an acetylene group into a Rh-C bond, a reductive elimination to form an oxazinoquinolinium-coordinated Rh(I) intermediate, an oxidative addition to break the N-O bond, and a protonation reaction to regenerate the active catalyst. The regioselectivity of the reaction has also been studied by using prop-1-yn-1-ylbenzene as a model unsymmetrical substrate. Theoretical calculations suggested that 1-phenyl-2-quinolinylpropanone would be the major product because of better conjugation between the phenyl group and enolate moiety in the corresponding transition state of the regioselectivity-determining step. These calculated data are consistent with the experimental observations.
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China).
authors.forename: Yingzi
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China).
authors.forename: Song
authors.initials: S
authors.lastname: Liu
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China).
authors.forename: Zisong
authors.initials: Z
authors.lastname: Qi
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China).
authors.forename: Xiaotian
authors.initials: X
authors.lastname: Qi
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China). xwli@dicp.ac.cn.
authors.forename: Xingwei
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China). lanyu@cqu.edu.cn.
authors.forename: Yu
authors.initials: Y
authors.lastname: Lan
keywords: CH bond activation; cleavage reactions; density function calculations; quinolines; rhodium