Thermal C-C bond cleavage reactions allow the construction of structurally diverse molecular skeletons via predictable and efficient bond reorganizations. Visible light photoredox-catalyzed radical-mediated C-C bond cleavage reactions have recently emerged as a powerful alternative method for overcoming the thermodynamic and kinetic barrier of C-C bond cleavage in diverse molecular scaffolds. In recent years, a plethora of elegant and useful reactions have been invented, and the products are sometimes otherwise inaccessible by classic thermal reactions. Considering the great influence and synthetic potential of these reactions, we provide a summary of the state of art visible light-driven radical-mediated C-C bond cleavage/functionalization strategies with a specific emphasis on the working models. We hoped that this review will be useful for medicinal and synthetic organic chemists and will inspire further reaction development in this interesting area.

Visible Light-Driven Radical-Mediated C-C Bond Cleavage/Functionalization in Organic Synthesis

In recent years, radical C–C bond cleavage reactions have been increasingly understood and used to perform transformations that complement traditional ionic processes. However, to date radical C–C bond cleavage/functionalization reactions have not been the subject of a dedicated review. Herein we summarize the most recent and significant developments in the radical activation and functionalization of carbon–carbon bonds, with an emphasis on both synthetic outcomes and reaction mechanisms, and highlight how these radical C–C bond cleavage reactions enable challenging transformations.

Cleavage of carbon-carbon bonds by radical reactions.

A visible-light-driven, copper-catalyzed three-component radical cross-coupling of oxime esters, styrenes, and boronic acids has been developed. Key steps of this protocol involve catalytic generation of an iminyl radical from a redox-active oxime ester and subsequent C-C bond cleavage to generate a cyanoalkyl radical. Upon its addition to styrene, the newly formed benzylic radical undergoes coupling with a boronic-acid-derived ArCuII complex to achieve 1,1-diarylmethane-containing alkylnitriles.

Copper-Catalyzed Radical Cross-Coupling of Redox-Active Oxime Esters, Styrenes, and Boronic Acids.

Just as "Deconstructivism" appeared as a novel movement in architecture in the 1980s, deconstructive approaches have recently emerged as excellent strategies for scaffold hopping modifications in chemistry. The deconstruction and functionalization of cyclic molecules mainly involves the cleavage of the carbon-carbon (C-C) bond followed by the construction of new bonds. The cleavage of inert C-C single bonds, especially in unstrained cycles, and their subsequent functionalization is still one of the most sought-after challenges in chemistry. In this vein, radical-mediated strategies provide an excellent approach for achieving this aim. This minireview is an outline of the history of homolytic cleavage and highlights the recent advances in exploring new chemical space by deconstructive functionalization.

Radical-Promoted C-C Bond Cleavage: A Deconstructive Approach for Selective Functionalization.

This article reviews synthetic transformations involving cleavage of a carbon–carbon bond of a four-membered ring, with a particular focus on the examples reported during the period from 2011 to th...

Cleavage of Carbon-Carbon σ-Bonds of Four-Membered Rings.

Cobalt has become increasingly attractive in homogeneous catalysis because of its unique characteristics and outstanding catalytic performance in addition to being cheap and earth-abundant. Hydride transfer processes are involved in a broad range of organic transformations that allow the facile preparation of various useful chemicals and synthetic building blocks. These reactions have continuously received great attention both from academia and industry. In this perspective, we review homogeneous cobalt-catalyzed hydride transfer reactions according to the classified reaction types and provide a comprehensive overview of the design, synthesis, and reactivity of cobalt catalysts, their catalytic applications, and reaction mechanisms.

Hydride Transfer Reactions Catalyzed by Cobalt Complexes.

Cu-Catalyzed Redox-Neutral Ring Cleavage of Cycloketone O-Acyl Oximes: Chemodivergent Access to Distal Oxygenated Nitriles

Polyacrylonitrile fiber (PANF), a common textile material in our daily life, which is a fine raw material for the synthesis of heterogeneous catalysts. More and more PANF-based heterogeneous catalysts have been developed and applied to organic transformations. In this paper, the research progress of PANF-based catalysts was reviewed, and the research progress of different PANF catalytic systems and their applications in green chemistry were emphatically introduced, which provided references for the development of PANF-supported catalytic technology. 

Polyacrylonitrile fiber‐based heterogeneous catalysts for organic transformations

Crystalline covalent organic frameworks (COFs) materials have good performance in photocatalytic conversions due to their excellent photoelectric properties in recent years. here, two new conjugated pyrene-based covalent organic frameworks (COFs), namely PyDF-COF and PyBMT-COF, were prepared through condensation polymerization of 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetraaniline and 2,5-difluoroterephthalaldehyde or 2,5-bis(methylthio)terephthalaldehyde, respectively. Highly selective aerobic hydroxylation of arylboronic acids can occur smoothly with high yields and a wide range of substrate universality. Compared with PyDF-COF, PyBMT-COF demonstrates a more efficient ability for this aerobic hydroxylation, indicating electron-donating thiomethyl groups of PyBMT-COF are more favorable to enhance distribution of electron cloud than electron-withdrawing fluorine groups of PyDF-COF, which make the PyBMT-COF more easily afford holes and electrons (h+-e-) separation, more effectively absorb visible light, and own narrower bandgap energy, higher photocurrent response, longer fluorescent lifetime and lower electrochemical impedance. 

Electronic-effect Regulated Covalent Organic Frameworks as Heterogeneous Photoactive Catalysts

A crystalline 2D nickel-coordinated bis(imino)pyridine metal–covalent organic framework (Ni-bipy-COF) material is easily fabricated by incorporating nickel ions into bis(imino)pyridine pincer COF skeleton. The Ni-bipy-COF catalyst can be applied to catalyze...

Wenying Ai

Papers

Hydride Transfer Reactions Catalyzed by Cobalt Complexes.

Cu-Catalyzed Redox-Neutral Ring Cleavage of Cycloketone O-Acyl Oximes: Chemodivergent Access to Distal Oxygenated Nitriles

Polyacrylonitrile fiber‐based heterogeneous catalysts for organic transformations

Electronic-effect Regulated Covalent Organic Frameworks as Heterogeneous Photoactive Catalysts

A Metal–Covalent Organic Framework Catalyst with Pincer Coordination Units for Boosting Transfer Hydrogenation of Quinolines with Ammonia Borane