Shining light on halogen-bonding complexes: a catalyst-free activation mode of carbon–halogen bonds for the generation of carbon-centered radicals

Chemical Science, Journal Year: 2023, Volume and Issue: 14(21), P. 5545 - 5568

Published: Jan. 1, 2023

This review provides a comprehensive overview on examples of how photochemical excitation halogen-bonding complexes can be useful for the generation carbon-centered radicals and their participation in synthetic organic transformations.

Language: Английский

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Organophotocatalytic Mechanisms: Simplicity or Naïvety? Diverting Reactive Pathways by Modifications of Catalyst Structure, Redox States and Substrate Preassemblies

ChemCatChem, Journal Year: 2023, Volume and Issue: 15(11)

Published: Feb. 21, 2023

Abstract Photocatalysis is a powerful tool to assemble diverse chemical scaffolds, yet bottleneck on its further development the understanding of multitude possible pathways when practitioners rely only oversimplified thermodynamic and optical factors. Recently, there growing number studies in field that exploit, inter alia , kinetic parameters organophotocatalysts are synthetically more programmable terms their redox states opportunities for aggregation with target substrate. Non‐covalent interactions play key role enables access new generation reactivities such as those open‐shell organophotocatalysts. In this review, we discuss how targeted structural modifications influence organophotocatalytic mechanisms together underlying principles. We also highlight benefits strategies preassembly static quenching overcome common reactivity issues (e. g., diffusion rate limits energetic limits).

Language: Английский

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Phenanthroline-Initiated Anti-selective Hydrosulfonylation of Unactivated Alkynes with Sulfonyl Chlorides

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(10), P. 6983 - 6993

Published: May 8, 2023

A simple and general method for anti-selective hydrosulfonylation of unactivated alkynes with sulfonyl chlorides in the presence a catalytic amount phenanthroline-based Lewis base (Me3Si)3SiH as hydrogen atom donor has been developed. The protocol proceeds efficiently under mild metal-free conditions, delivering diverse set (Z)-vinyl sulfones high stereoselectivity. Additionally, displays excellent functional-group compatibility can be applied to late-stage modifications complex drugs their derivatives. Experimental density functional theory studies unveiled that key transformation's success is employment base, which interacts form halogen-bond accelerates cleavage S–Cl bonds irradiation visible light.

Language: Английский

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Photogeneration of α-Bimetalloid Radicals via Selective Activation of Multifunctional C1 Units

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(23), P. 15850 - 15859

Published: May 28, 2024

Light-driven strategies that enable the chemoselective activation of a specific bond in multifunctional systems are comparatively underexplored comparison to transition-metal-based technologies, yet desirable when considering controlled exploration chemical space. With current drive discover next-generation therapeutics, reaction design enables strategic incorporation an sp3 carbon center, containing multiple synthetic handles for subsequent space would be highly enabling. Here, we describe photoactivation ambiphilic C1 units generate α-bimetalloid radicals using only Lewis base and light source directly activate C–I bond. Interception these transient with various SOMOphiles rapid synthesis organic scaffolds (B, Si, Ge) orthogonal activation. In-depth theoretical mechanistic studies reveal prominent role 2,6-lutidine forming photoactive charge transfer complex stabilizing situ generated iodine radicals, as well influential boron p-orbital activation/weakening This simple efficient methodology enabled expedient access functionalized 3D frameworks can further derivatized available technologies C–B C–Si

Language: Английский

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Photochemical Synthesis of Lactones, Cyclopropanes and ATRA Products: Revealing the Role of Sodium Ascorbate**

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: unknown

Published: Feb. 7, 2024

Abstract Light‐mediated processes have received significant attention, since they re‐surfaced unconventional reactivity platforms, complementary to conventional polar chemistry. γ‐Lactones and cyclopropanes are prevalent moieties, found in numerous natural products pharmaceuticals. Among various methods for their synthesis, light‐mediated protocols coming the spotlight, although these contingent upon use of photoorgano‐ or metal‐based catalysts. Herein, we introduce a novel photochemical activation iodo‐reagents via cheap sodium ascorbate ascorbic acid enable homolytic scission addition onto double bonds. The developed protocol was applied successfully formal [3+2] cycloaddition synthesis γ‐lactones, traditional atom transfer radical (ATRA) reactions one‐pot two‐step conversion alkenes cyclopropanes. In all cases, desired were obtained good high yields, while reaction mechanism thoroughly investigated. Depending on nature iodo‐reagent, halogen hydrogen‐bonded complex is formed, which initiates process.

Language: Английский

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Synthesis of Vinyl and 1,3‐Dienyl Sulfones Enabled by Photochemical Excitation of Halogen‐Bonding Complexes

Advanced Synthesis & Catalysis, Journal Year: 2024, Volume and Issue: 366(6), P. 1422 - 1429

Published: Feb. 1, 2024

Abstract The photochemical catalyst‐free radical‐based synthesis of vinyl and 1,3‐dienyl sulfones is disclosed. Mechanistic investigations support that the transformations rely on a visible‐light‐promoted activation halogen‐bonding complex, which formed between an alkenyl (or 1,3‐dienyl) bromide sodium sulfinate salt. reactions exhibit wide functional group tolerance (compatible with heteroatoms, electron‐withdrawing electron‐donating groups), finding application in structural modification biologically relevant molecules. Eventually, continuous flow protocol was developed to upscale these transformations.

Language: Английский

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The synergism of sequential paired electrosynthesis with halogen bonding activation for the cyclization of organochlorides with olefins

Science China Chemistry, Journal Year: 2022, Volume and Issue: 66(2), P. 540 - 547

Published: Dec. 14, 2022

Language: Английский

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Direct Light‐Enabled Access to α‐Boryl Radicals: Application in the Stereodivergent Synthesis of Allyl Boronic Esters**

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(34)

Published: June 16, 2023

Abstract Operationally simple strategies to assemble boron containing organic frameworks are highly enabling in synthesis. While conventional retrosynthetic logic has engendered many platforms focusing on the direct formation of C−B bonds, α‐boryl radicals have recently reemerged as versatile open‐shell alternatives access organoborons via adjacent C−C bond formation. Direct light‐enabled α‐activation is currently contingent photo‐ or transition metal‐catalysis activation efficiently generate radical species. Here, we disclose a facile α‐halo boronic esters using only visible light and Lewis base enable homolytic scission. Intermolecular addition styrenes facilitates rapid construction E ‐allylic esters. The simplicity permits strategic merger this construct with selective energy transfer catalysis complimentary stereodivergent synthesis Z

Language: Английский

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Electrochemical Atom Transfer Radical Addition of Polychloroalkanes to Olefins Promoted by 4,4‐Di‐tert‐butyl Bipyridine

Chinese Journal of Chemistry, Journal Year: 2023, Volume and Issue: 41(13), P. 1583 - 1588

Published: Feb. 14, 2023

Comprehensive Summary A new electrochemical strategy for the atom transfer radical addition (ATRA) of polychloroalkanes across olefins has been realized by synergism paired electrolysis and halogen bonding activation. Notably, readily accessible 4,4‐di‐ tert ‐butyl bipyridine (dtbpy), acting as a acceptor, shifted reduction potential C—Cl bonds positively 110 mV. The decreased operating leads to wide substrate scope excellent functional group compatibility. diverse array terminal internal alkenes such (hetero)aryl olefins, unactive aliphatic natural products drugs‐derived were well compatible.

Language: Английский

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Coupling of α-bromoamides and unactivated alkenes to form γ-lactams through EDA and photocatalysis

Chemical Science, Journal Year: 2023, Volume and Issue: 14(6), P. 1569 - 1574

Published: Jan. 1, 2023

γ-Lactams are prevalent in small-molecule pharmaceuticals and provide useful precursors to highly substituted pyrrolidines. Despite numerous methods for the synthesis of this valuable motif, previous redox approaches γ-lactam from α-haloamides olefins require additional electron withdrawing functionality as well N-aryl substitution promote electrophilicity intermediate radical prevent competitive O-nucleophilicity about amide. Using α-bromo imides α-olefins, our strategy enables monosubstituted protected γ-lactams a formal [3 + 2] fashion. These species poised further derivatization into more complex heterocyclic scaffolds, complementing existing methods. C-Br bond scission occurs through two complementary approaches, formation an donor-acceptor between bromoimide nitrogenous base which undergoes photoinduced transfer, or triplet sensitization with photocatalyst, furnish electrophilic carbon-centered radical. The addition Lewis acids allows increased radical, enabling tertiary α-Br-imides be used coupling partners internal olefins.

Language: Английский

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