Recent Advances in Visible Light Induced Palladium Catalysis

Sarkar, Sumon; Cheung, Kelvin Pak Shing; Gevorgyan, Vladimir

doi:10.1002/anie.202311972

Cited by 13 publications

(5 citation statements)

References 99 publications

(154 reference statements)

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“…Transition metal catalysis at its photoexcited states has attracted significant attention for the discovery of unprecedented transformations. − In contrast to metallaphotoredox catalysis, which employs photosensitizers and transition metals synergistically, − photoexcited transition metal catalysis uses a single transition metal complex to harvest light and enable bond forming or breaking events. However, the double duty of transition metal catalysis makes the asymmetric version of this catalytic mode formidably challenging, and few enantioselective excited transition metal catalytic transformations were reported. − Very recently, our group succeeded in achieving the kinetic resolution of 2-styrylpyrrolidines enabled by photoexcited chiral copper complex-mediated alkene E → Z isomerization .…”

Section: Introductionmentioning

confidence: 99%

Photoexcited Palladium-Catalyzed Deracemization of Allenes

Song,

Bai,

et al. 2024

J. Am. Chem. Soc.

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The different enantiomers of specific chiral molecules frequently exhibit disparate biological, physiological, or pharmacological properties. Therefore, the efficient synthesis of single enantiomers is of particular importance not only to the pharmaceutical sector but also to other industrial sectors, such as agrochemical and fine chemical industries. Deracemization, a process during which a racemic mixture is converted into a nonracemic product with 100% atom economy and theoretical yield, is the most straightforward method to access enantioenriched molecules but a challenging task due to a decrease in entropy and microscopic reversibility. Axially chiral allenes bear a distinctive structure of two orthogonal cumulative π-systems and are acknowledged as synthetically versatile synthons in organic synthesis. The selective creation of axially chiral allenes with high optical purity under mild reaction conditions has always been a very popular and hot topic in organic synthesis but remains challenging. Herein, a photoexcited palladium-catalyzed deracemization of nonprefunctionalized disubstituted allenes is disclosed. This method provides an efficient and economical strategy to accommodate a broad scope of allenes with good enantioselectivities and yields (53 examples, up to 96% yield and 95% ee). The use of a suitable chiral palladium complex with visible light irradiation is an essential factor in achieving this transformation. A metal-to-ligand charge transfer mechanism was proposed based on control experiments and density functional theory calculations. Quantum mechanical studies implicate dual modes of asymmetric induction behind our new protocol: (1) sterically controlled stereoselective binding of one allene enantiomer under the ground-state and (2) facile, noncovalent interaction-driven excited-state isomerization toward the opposite enantiomer. The success of this newly established photochemical deracemization strategy should provide inspiration for expansion to other multisubstituted allenes and will open up a new mode for enantioselective excited-state palladium catalysis.

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Section: Introductionmentioning

confidence: 99%

Photoexcited Palladium-Catalyzed Deracemization of Allenes

Song,

Bai,

et al. 2024

J. Am. Chem. Soc.

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“…With the advancement of chemistry, the range of substrates that can react with palladium has been expanded, enabling access to various compounds. In recent years, the utilization of photoexcited Pd species has emerged as a prominent and significant field within palladium chemistry . Photoexcited Pd species engage in reactions with alkyl halides via single electron transfer (SET), forming hybrid Pd radicals that are used in various coupling reactions (Scheme a).…”

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confidence: 99%

Ketyl Radical Generation by Photoexcited Palladium and Development of Organopalladium-Type Reactions

Tanaka

2024

ACS Catal.

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Enabling reactions of traditional substrates that are inert to Pd catalysts has the potential for further advancements in the field of Pd chemistry. In this study, we developed a method for generating ketyl radicals through the reaction of a photoexcited Pd species with ketones. Upon subsequent reaction with olefins, the ketyl radicals generated through this method yielded Pd-specific reductive and Heck-type coupling products. Mechanistic studies indicated that the proposed radical generation method exhibits characteristics distinct from those of traditional methods such as SmI 2 reduction and photoredox-catalyzed reactions.

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“…Visible-light-induced palladium catalysis has emerged as a promising photocatalysis method, which has enabled a wide array of radical-based transformations and challenges from conventional palladium chemistry to be tackled . Compared to those of other metal photocatalysts (Ir or Rh complex) and organic photosensitizers, the excited Pd complex has a stronger reduction potential (−2.51 V vs Fc + /Fc) and can effectively cleave the C–X bond of inactive alkyl halides to generate Pd(I)-alkyl radical species A .…”

mentioning

confidence: 99%

Photoinduced Palladium-Catalyzed 1,2-Aminoalkylation of Aromatic Alkenes with Hydroxyl as the Directing Group

Yang,

Li,

Guo

et al. 2024

Org. Lett.

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The hybrid nature of Pd(I)-alkyl radical species has enabled a wide array of radical-based transformations. However, in this transformation, the secondary Pd(I)-alkyl radical species are prone to recombining into Pd(II)-alkyl species to give Heck-type products via β-H loss. Herein, we report a visible-light-induced, three-component Pd-catalyzed 1,2-aminoalkylation of alkenes with readily available alkyl halides and amines to construct C−C and C−N bonds simultaneously. Mechanistic investigation shows that the intermediate of o-quinone methide produced is the key factor in the transformation.

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Recent Advances in Visible Light Induced Palladium Catalysis

Cited by 13 publications

References 99 publications

Photoexcited Palladium-Catalyzed Deracemization of Allenes

Photoexcited Palladium-Catalyzed Deracemization of Allenes

Ketyl Radical Generation by Photoexcited Palladium and Development of Organopalladium-Type Reactions

Photoinduced Palladium-Catalyzed 1,2-Aminoalkylation of Aromatic Alkenes with Hydroxyl as the Directing Group

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