C–H activation: A strategic approach toward lactams using transition metals

Rhodium-Catalyzed Asymmetric C–H Functionalization Reactions

“…Among these, transition-metal-catalyzed asymmetric C–H functionalization reactions have provided powerful access to the synthesis of diverse enantioenriched compounds in a highly enantioselective manner. − Generally speaking, there are three different pathways for achieving asymmetric C–H functionalization reactions, desymmetrization, kinetic resolution, and the addition to unsaturated compounds (Scheme ). Asymmetric C–H functionalization reactions can be catalyzed by various transition-metal complexes including palladium (Pd), − rhodium (Rh), − iridium (Ir), − ruthenium (Ru), − and other 3d transition metals. − Among these, Pd and Rh catalysts have received the most attention due to their applications in diverse enantioselective reactions with broad substrate scope. In this regard, Pd-catalyzed asymmetric C–H functionalization reactions have been extensively investigated and well-reviewed.…”

Regio- and Enantioselective Catalytic δ-C–H Amidation of Dioxazolones Enabled by Open-Shell Copper-Nitrenoid Transfer

“…Recently, direct intramolecular C–H amidation has garnered significant attention as an efficient route for accessing cyclic amides. , In recent years, our group and others have successfully showcased a series of catalytic amidation reactions to obtain five-membered cyclic amides (γ-lactams) from 1,4,2-dioxazol-5-ones. − Notably, the in situ generated iridium-nitrenoid species bearing chiral aminoquinoline or diamine ligands was proposed to insert into C–H or CC bonds in an asymmetric manner to furnish chiral γ-lactam products. − Likewise, their accessibility via C­(sp 3 )–H amidation has also been accomplished by Yu et al (Ru), Chen et al (Ir), and Meggers et al (Ru) . Despite these successes in asymmetric γ-lactam synthesis via metal-nitrenoid transfer, to the best of our knowledge, an asymmetric intramolecular δ-C­(sp 3 )–H amidation reaction to access chiral six-membered lactams remains elusive so far, likely due to the following challenges: (1) the regioselectivity issue, which becomes more prominent when substrates contain potentially competing γ- and δ-C–H bonds within the same molecule, and (2) the difficulty of asymmetric C–N bond formation under the presently known mechanistic approaches, thus requiring a new catalytic system for the chiral δ-lactam synthesis via formal C–H amidation.…”

“…Recently, direct intramolecular C−H amidation has garnered significant attention as an efficient route for accessing cyclic amides. 25,26 In recent years, our group and others have successfully showcased a series of catalytic amidation reactions to obtain five-membered cyclic amides (γ-lactams) from 1,4,2dioxazol-5-ones. 27−29 Notably, the in situ generated iridiumnitrenoid species bearing chiral aminoquinoline or diamine ligands was proposed to insert into C−H or C�C bonds in an asymmetric manner to furnish chiral γ-lactam products.…”

Visible‐Light‐Mediated Energy Transfer Enables the Synthesis of β‐Lactams via Intramolecular Hydrogen Atom Transfer

“…In this study, we wanted to investigate whether β-lactams could be accessed from simpler, more benign precursors, by harnessing visible-lightmediated energy transfer to enable novel CÀ H bond functionalization reactions. [6,7] Direct CÀ H bond functionalization reactions are amongst the most powerful methods in modern synthetic chemistry, especially when they enable functionalization of unactivated C(sp 3 )À H bonds. [8][9][10] Such reactions are usually based on transition metal-catalyzed activation [9] and/or the use of directing groups.…”