Catalytic Dehydrogenative Cyclization of <i>o</i>‐Teraryls under pH‐Neutral and Oxidant‐Free Conditions

Tsukamoto, Tatsuhiro; Dong, Guangbin

doi:10.1002/anie.202004719

Cited by 27 publications

(12 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As for substrates containing benzofuran or a benzothiophene ring, the desired dehydrogenation products ( P29 , P30 ) were accompanied by fused aromatic compounds ( P29′ , P30′ ). The latter are probably produced from ( Z ) -P29 and ( Z ) -P30 via a 6π electrocyclization/SET/HAT sequence (a similar pathway has been reported by Dong for catalytic dehydrogenative cyclization of o -teraryls).…”

Section: Results and Discussionsupporting

confidence: 62%

Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis

et al. 2021

View full text Add to dashboard Cite

The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non-or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for roomtemperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H 2 . This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.

show abstract

Section: Results and Discussionsupporting

confidence: 62%

Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis

et al. 2021

View full text Add to dashboard Cite

show abstract

“…Driven by the aromatization of the benzene ring, the proton lost from the highly reactive intermediate B to C in the photoinduced electron transfer (PET) cycle is associated with a SET from intermediate B to reduce Ir IV to Ir III . Subsequently, a SET/deprotonation from radical C to Co II and followed by Co I -mediated protonation or direct hydrogen atom transfer (HAT) between the Co II and intermediate C would afford Co III -H and the final product 2a . Finally, Co III –H reacted with another proton to release H 2 (Figure S1) and regenerate Co III , completing the reaction circle.…”

Section: Results and Discussionmentioning

confidence: 99%

Synthesis of 10-PhenanthrenolsviaPhotosensitized Triplet Energy Transfer, Photoinduced Electron Transfer, and Cobalt Catalysis

Yang

Shen

et al. 2022

J. Org. Chem.

View full text Add to dashboard Cite

Due to the inert redox activity and high triplet energy, radical chemistry of 1,3-dicarbonyl compounds usually requires prefunctionalization substrates, external oxidant, and high-energy UV light. Here, we report a visible-light-driven photocatalyst/cobaloxime system composed of a photosensitized energy transfer reaction (PEnT) and photoinduced electron transfer reaction (PET) and with an interrupted 6π-photocyclization/dehydrogenative aromatization in one pot to synthesize 10-phenanthrenols. Preliminary mechanistic studies revealed that fac-Ir(ppy)3 plays the dual roles of energy transfer catalysis for photocycloaddition via 1,2-biradical intermediates of 1,3-dicarbonyl compounds and photoredox/cobaloxime catalysis dehydrogenative aromatization of 1,4-biradical rather than the intermediates via 6π photocyclization in the tandem reaction. In contrast to previous well-established radical chemistry of 1,3-dicarbonyl compounds, we provide a new strategy for the activation of 1,3-dicarbonyl compounds under visible light catalysis, affording a novel cyclization strategy with extremely high atom economy for the synthesis of 10-phenanthrenols.

show abstract

“…The allylic C−H bond can also be abstracted readily by the cobaloxime catalyst to form cobalt‐hydride species, leveraging hydrogen evolution in the catalytic system. In 2020, the Dong group disclosed a catalytic acceptorless dehydrogenative cyclization of o ‐teraryls 56 , [35] obviating the usage of any strong acids and oxidants that were employed extensively in the Scholl and Mallory oxidation [36] . By employing Co(dmg(BF 2 )) 2 (OH 2 ) 2 57 as the sole catalyst and irradiating under 254 nm light, a number of desired triphenylene products 58 were obtained in good yields (Scheme 14).…”

Section: Cobalt Catalysismentioning

confidence: 99%

Metal‐Catalyzed Hydrogen Evolution Reactions Involving Strong C−H Bonds Activation via Hydrogen Atom Transfer

Zhang

Hui

et al. 2021

ChemCatChem

View full text Add to dashboard Cite

Hydrogen evolution reactions have been proved to be a powerful and green strategy in organic synthesis. Differing from hydrogen evolution reactions catalyzed by noble metal pincer complex with some limitations, the reactions facilitated by merging hydrogen atom transfer (HAT) and metal‐catalyzed hydrogen evolution (MCHE) represents a more attractive and promising alternative for direct formation of chemical bonds from available feedstocks in synthetic chemistry. Given the significance, this review summarizes the state of the art with highlighting the mechanism, synthetic applications and meanwhile enlightens the future development of this area.

show abstract

Catalytic Dehydrogenative Cyclization of o‐Teraryls under pH‐Neutral and Oxidant‐Free Conditions

Cited by 27 publications

References 63 publications

Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis

Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis

Synthesis of 10-PhenanthrenolsviaPhotosensitized Triplet Energy Transfer, Photoinduced Electron Transfer, and Cobalt Catalysis

Metal‐Catalyzed Hydrogen Evolution Reactions Involving Strong C−H Bonds Activation via Hydrogen Atom Transfer

Contact Info

Product

Resources

About