Visible‐Light‐Induced, Single‐Metal‐Catalyzed, Directed C−H Functionalization: Metal‐Substrate‐Bound Complexes as Light‐Harvesting Agents

Abstract

CÀ H functionalization represents one of the most rapidly advancing areas in organic synthesis and is regarded as one of the key concepts to minimize the ecological and economic footprint of organic synthesis. The ubiquity and low reactivity of CÀ H bonds in organic molecules, however, poses several challenges, and often necessitates harsh reaction conditions to achieve this goal, although it is highly desirable to achieve CÀ H functionalization reactions under mild conditions. Recently, several reports uncovered a conceptually new approach towards CÀ H functionalization, where a single transition-metal complex can be used as both the photosensitizer and catalyst to promote CÀ H bond functionalization in the absence of an exogeneous photosensitizer. In this Minireview, we will provide an overview on recent achievements in CÀ H functionalization reactions, with an emphasis on the photochemical modulation of the reaction mechanism using such catalysts.

A ligand-enabled metallaphotoredox protocol for Suzuki-Miyaura cross-couplings for the synthesis of diarylmethanes

“…Significant progress has been made to meet chemists’ aspirations for more efficient chemical synthesis ( Li, 2016 ; Li et al., 2021c , 2022a ). In this area, state-of-the-art solutions include Fu’s strategy leveraging multiligand cooperativity ( Chen et al., 2021 ), Ackermann’s and Greaney’s light-harvesting metal-substrate bound complexes ( Gandeepan et al., 2019 ; Sagadevan and Greaney, 2019 ), metal-embedded covalent-organic framework ( Vijeta et al., 2022 ), among others ( Pei et al., 2022 ). In these elegant precedents, photosensitive species are either generated in situ or incorporated into the conventional ligated metal catalysts, therefore, circumventing exogeneous photocatalysts.…”

Simplifying the Synthesis of Nonproteinogenic Amino Acids via Palladium-Catalyzed δ-Methyl C–H Olefination of Aliphatic Amines and Amino Acids

“…Although multicomponent or tandem reactions proceeding via highly reactive intermediates seem to be the most approachable route, often they suffer from multiple synthetic steps, low productivity, and poor stereoselectivity. In this context, transition metal-catalyzed C–H functionalization can offer a simple and straightforward solution. − Particularly, palladium-catalyzed α -, β -, and γ -C­( sp 3 )–H functionalizations of different proteinogenic αAAs have come up as a very powerful tool in the last 10 years. − Very recently, our group has explored arylation and borylation at the distal δ- position of leucine. In 2021, Carretero and co-workers also demonstrated δ-arylation of different γ-unblocked αAA derivatives using a sulfonamide linker …”

Two-in-one metallaphotoredox cross-couplings enabled by a photoactive ligand

“…[45][46][47][48][49] However, because of the metal-substrate binding, these single-catalyst strategies are often metal dependent, substrate specific, and mostly accompanied by sophisticated ligands. 50 Therefore, such reactivities of catalyst-substrate pairs cannot be easily…”