Bromoacetic Acid-Promoted Nonheme Manganese-Catalyzed Alkane Hydroxylation Inspired by α-Ketoglutarate-Dependent Oxygenases

Citations Over TimeTop 12% of 2022 papers

Abstract

Biomimetic iron and manganese complexes have emerged as important catalysts in chemo-, regio-, and stereoselective oxidation reactions. In this study, we describe a remote hydroxylation of undirected C(sp3)–H bonds utilizing a simple manganese complex as a catalyst and hydrogen peroxide (H2O2) as a terminal oxidant in the presence of bromoacetic acid (BrCH2CO2H) as an additive. Crucial features of this catalytic system are the excellent catalytic activity of an easily preparable manganese catalyst, [Mn(R,R-BPMCN)]2+ (1), a low catalyst loading, a short reaction time, a broad substrate scope, and an easy scale-up. Mechanistic studies were also performed to elucidate the role of BrCH2CO2H and the nature of the hydroxylating intermediate, revealing that the BrCH2CO2H additive facilitates the generation of a highly electrophilic Mn(V)–oxo bromoacetate intermediate as a responsible oxidant via a heterolytic O–O bond cleavage of a postulated Mn(III)–OOH precursor. One notable observation in the mechanistic studies was that a significant amount of 18O was incorporated from H218O into the alcohol product in these catalytic oxidation reactions. On the basis of the above experimental observations and from the support of density functional theory (DFT) calculations, we conclude that a highly electrophilic Mn(V)–oxo bromoacetate complex was generated as a responsible oxidant that effects the undirected C(sp3)–H hydroxylation via an oxygen-rebound mechanism, thus mimicking both the structure and the function of the active intermediate of iron(IV)–oxo succinate for α-ketoglutarate (αKG)-dependent nonheme iron oxygenases.

Related Papers

• → Protein Hydroxylation Catalyzed by 2-Oxoglutarate-dependent Oxygenases(2015)174 cited
• → Heterolytic Cleavage of Hydrogen Molecule by Rhodium Thiolate Complexes That Catalyze Chemoselective Hydrogenation of Imines under Ambient Conditions(2009)52 cited
• → Oxygen insertion into the metal–carbon bond of cyclopalladated 2-(alkylsulphinyl)azobenzenes by peracids. High yield regiospecific aromatic hydroxylation(1988)29 cited
• → pH Dependent Photodeprotection of Formaldehyde: Homolytic C–C Scission in Acidic Aqueous Solution versus Heterolytic C–C Scission in Basic Aqueous Solution(2017)1 cited
• → Pressure effects as mechanistic probes for homolytic thermal cobaltcarbon bond cleavage of cobalamins(1992)9 cited