Transition Metal-Catalyzed Direct Stereoselective Oxygenations of C(sp³)–H Groups

Abstract

Designing catalytic approaches to deliberate and selective C−H activation was listed by Bergman among the "Holy Grails" of synthetic chemistry in 1995, and continues to be a hot topic up to now, mostly in the context of late-stage functionalization of complex molecular structures (Acc.

A New Age of Biocatalysis Enabled by Generic Activation Modes

“…A common reaction mode catalyzed by transition metals is atom/group transfer. , Transition metals such as iron have a wide range of oxidation states which enable the formation of reactive (high-valent) species such as metal-carbenes, metal-nitrenes, or metal-oxo compounds (Figure a). These intermediates are highly reactive and participate in many different types of reactions, including insertion into CC and C–H bonds, enabling a diverse range of functionalizations. − Using metal-carbenes as an example, a general (simplified) catalytic cycle begins with the formation of the intermediate via transfer of electrons and removal of a leaving group (e.g., N 2 in the case of a diazo compound as a carbene precursor). The metal-carbene can then, for example, undergo HAT from a substrate followed by radical rebound or directly insert into a specific bond .…”

“…These intermediates are highly reactive and participate in many different types of reactions, including insertion into C=C and C–H bonds, enabling a diverse range of functionalizations. 84 − 86 Using metal-carbenes as an example, a general (simplified) catalytic cycle begins with the formation of the intermediate via transfer of electrons and removal of a leaving group (e.g., N 2 in the case of a diazo compound as a carbene precursor). The metal-carbene can then, for example, undergo HAT from a substrate followed by radical rebound or directly insert into a specific bond.…”

Electrochemical C(sp3)−H Functionalization Using Acetic Acid as a Hydrogen Atom Transfer Reagent

“…The development of a methodology for the functionalization of unreactive C(sp 3 )À H bonds, which are ubiquitous in many organic compounds, is an important research topic. [1][2][3][4] Owing to their mild and selective nature, such transformations have a wide range of applications, e. g., in the synthesis of pharmaceuticals, natural products, and polymers. [5][6][7][8][9] Traditional approaches to the functionalization of C(sp 3 )À H bonds require the prefunctionalization of substrates via costly chemical reactions.…”

A synthetically useful catalytic system for aliphatic C–H oxidation with a nonheme cobalt complex and m-CPBA

“…3,4 Inspired by the structural characteristics of the catalytic metal center and the reaction mechanisms that underline their enzymatic function as catalysts for aerobic oxidative transformations, numerous iron and manganese complexes bearing porphyrinic or non-porphyrinic ligands have been developed for the selective oxidation of aliphatic C(sp 3 )–H bonds via well-established mechanisms of hydrogen atom transfer (HAT) followed by oxygen rebound. 5–15 As a result, significant advances have been made in the selective oxidation of alkanes based on intrinsic factors, such as bond strength, electronic effect, steric effect, stereoelectronic effect, directing group, chirality, and more recently, medium effect and non-covalent interactions in the secondary coordination sphere. 5 Moreover, since the identification of the first two iron( iv )-oxo complexes in enzymatic and biomimetic studies in 2003, 16,17 mechanistic studies have also advanced greatly through synthesis, spectroscopic characterization and kinetic studies of high-valent metal-oxo intermediates.…”