title: Mechanistic insights into bicyclic guanidine-catalyzed reactions from microscopic and macroscopic perspectives.
abstract: Chiral bicyclic guanidine can act as an efficient chiral Brønsted base catalyst in enantioselective reactions, delivering good yields with high enantioselectivities. There is interest in understanding the detailed mechanisms of these guanidine-catalyzed reactions. Herein, we performed a detailed kinetic study of three different types of chiral bicyclic guanidine-catalyzed reactions, determining the bifunctionality of our guanidine catalyst. Although these three reactions share a similar catalytic cycle, their intrinsic kinetic behaviors are significantly different from each other because of the difference in the rate-determining step. The calculated theoretical rate expression for each reaction, as a result of the mechanism elucidated with density functional theory calculations, agrees well with the respective experimentally observed rate equation.
authors.affiliation: †Department of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Hansong
authors.initials: H
authors.lastname: Xue
authors.affiliation: †Department of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Danfeng
authors.initials: D
authors.lastname: Jiang
authors.affiliation: †Department of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Huan
authors.initials: H
authors.lastname: Jiang
authors.affiliation: †Department of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Choon Wee
authors.initials: CW
authors.lastname: Kee
authors.affiliation: †Department of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Hajime
authors.initials: H
authors.lastname: Hirao
authors.affiliation: §Department of Chemistry, Kyoto University, Sakyo-ku, Kyoto 6068502, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: ‡Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
authors.forename: Ming Wah
authors.initials: MW
authors.lastname: Wong
authors.affiliation: †Department of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
authors.forename: Choon-Hong
authors.initials: CH
authors.lastname: Tan