title: Enzyme-like catalysis via ternary complex mechanism: alkoxy-bridged dinuclear cobalt complex mediates chemoselective O-esterification over N-amidation.
abstract: Hydroxy group-selective acylation in the presence of more nucleophilic amines was achieved using acetates of first-row late transition metals, such as Mn, Fe, Co, Cu, and Zn. Among them, cobalt(II) acetate was the best catalyst in terms of reactivity and selectivity. The combination of an octanuclear cobalt carboxylate cluster [Co4(OCOR)6O]2 (2a: R = CF3, 2b: R = CH3, 2c: R = (t)Bu) with nitrogen-containing ligands, such as 2,2'-bipyridine, provided an efficient catalytic system for transesterification, in which an alkoxide-bridged dinuclear complex, Co2(OCO(t)Bu)2(bpy)2(μ2-OCH2-C6H4-4-CH3)2 (10), was successfully isolated as a key intermediate. Kinetic studies and density functional theory calculations revealed Michaelis-Menten behavior of the complex 10 through an ordered ternary complex mechanism similar to dinuclear metallo-enzymes, suggesting the formation of alkoxides followed by coordination of the ester.
authors.affiliation: Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Stefano
authors.initials: S
authors.lastname: Santoro
authors.forename: Yuki
authors.initials: Y
authors.lastname: Azuma
authors.forename: Fahmi
authors.initials: F
authors.lastname: Himo
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohshima
authors.forename: Kazushi
authors.initials: K
authors.lastname: Mashima
mesh_terms: D000215:Acylation; D000438:Alcohols / Q000737:chemistry; D000577:Amides / Q000138:chemical synthesis*; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004798:Enzymes / Q000737:chemistry*; D004952:Esters / Q000138:chemical synthesis*; D007700:Kinetics; D008958:Models, Molecular; D010636:Phenols / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D028561:Transition Elements / Q000737:chemistry
chemical_list: D000438:Alcohols; D000577:Amides; D004798:Enzymes; D004952:Esters; D010636:Phenols; D028561:Transition Elements; C059688:alkoxyl radical; D003035:Cobalt