Energy transfer photocatalysis: exciting modes of reactivity

Chemical Society Reviews, Journal Year: 2024, Volume and Issue: 53(3), P. 1068 - 1089

Published: Jan. 1, 2024

Leveraging light energy to expose the ‘dark’ reactive states describes whole essence of triplet–triplet transfer. This offers an impressive opportunity conduct a multitude diverse reactions and access sought-after molecular motifs.

Language: Английский

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Catalytic Photochemical Deracemization via Short‐Lived Intermediates

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(50)

Published: July 10, 2023

Upon irradiation in the presence of a suitable chiral catalyst, racemic compound mixtures can be converted into enantiomerically pure compounds with same constitution. The process is called photochemical deracemization and involves formation short-lived intermediates. By opening different reaction channels for forward to intermediate re-constitution molecule, entropically disfavored becomes feasible. Since discovery first 2018, field has been growing rapidly. This review comprehensively covers research performed area discusses current developments. It subdivided according mode action respective substrate classes. focus this on scope individual reactions discussion mechanistic details underlying presented reaction.

Language: Английский

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Creating a Defined Chirality in Amino Acids and Cyclic Dipeptides by Photochemical Deracemization

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(47)

Published: Oct. 4, 2023

Abstract 2,5‐Diketopiperazines are cyclic dipeptides displaying a wide range of applications. Their enantioselective preparation has now been found possible from the respective racemates by photochemical deracemization (53 examples, 74 % to quantitative yield, 71–99 ee ). A chiral benzophenone catalyst in concert with irradiation at λ=366 nm enables establish configuration stereogenic carbon atom C6 will. If other centers present diketopiperazines they remain unaffected and stereochemical editing is single position. Consecutive reactions, including conversion into N ‐aryl or ‐alkyl amino acids reduction piperazines, occur without compromising newly created center. Transient absorption spectroscopy revealed that processes one enantiomer 2,5‐diketopiperazines preferentially reversible hydrogen transfer responsible for process. The remarkably long lifetime protonated ketyl radical implies yet unprecedented mode action.

Language: Английский

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Photochemical Deracemization of Lactams with Deuteration Enabled by Dual Hydrogen Atom Transfer

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 18, 2024

Photochemical deracemization has emerged as one of the most straightforward approaches to access highly enantioenriched compounds in recent years. While excited-state events such energy transfer, single electron and ligand-to-metal charge transfer have been leveraged promote stereoablation, relying on hydrogen atom which circumvent limitations imposed by triplet redox potential racemic substrates, remain underexplored. Conceptually, attractive method for tertiary stereocenter might be abstraction followed donation. However, implementing a strategy poses significant challenges, primarily because products are also reactive if chiral catalyst is unable differentiate between two enantiomers. Herein we report distinct dual photochemical δ- γ-lactams, achieving high enantioenrichment deuterium incorporation despite inherent reactivity products. Mechanistic studies reveal that benzophenone enables nonselective while tetrapeptide-derived thiol dictates enantioselectivity donation step. More importantly, pyridine-based alcohol was found play crucial roles facilitating well enhancing

Language: Английский

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Asymmetric photoreactions catalyzed by chiral ketones

RSC Advances, Journal Year: 2025, Volume and Issue: 15(4), P. 2874 - 2889

Published: Jan. 1, 2025

Asymmetric catalytic reactions are essential for synthesizing chiral drugs and fine chemicals, with their stereoselectivity influenced significantly by interactions between catalysts substrates.

Language: Английский

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Stereochemical Editing at sp³-Hybridized Carbon Centers by Reversible, Photochemically Triggered Hydrogen Atom Transfer

Accounts of Chemical Research, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 19, 2025

ConspectusMillions of chiral compounds contain a stereogenic sp3-hybridized carbon center with hydrogen atom as one the four different substituents. The can be edited in an increasing number cases by selective transfer (HAT) to and from photocatalyst. This Account describes development photochemical deracemization reactions using oxazole-annulated benzophenones bonding motif that allows them recognize lactam substrates two-point bonding. backbone catalysts consists azabicyclo[3.3.1]nonan-2-one U-shaped geometry, which enables substrate recognition occur parallel benzoxazole part aromatic ketones. photocatalysts facilitate catalytic several compound classes including hydantoins, N-carboxyanhydrides, oxindoles, 2,5-diketopiperazines, 4,7-diaza-1-isoindolinones. In addition, if more than is present, editing delivers distinct diastereoisomer upon appropriate selection respective photocatalyst enantiomer. operate via benzophenone triplet selectively abstracts properly positioned exclusively two enantiomers. step creates planar carbon-centered radical erases absolute configuration at this position. While returning HAT same position would likely recreate configuration, spectroscopic quantum chemical studies suggest delivered heteroatom conjugation center. Two scenarios distinguished for shuttling process. For 4,7-diaza-1-isoindolinones, back occurs carbonyl oxygen or imine-type nitrogen not involved binding catalyst. oxindoles single group available accept atom. It currently assumed group, although comparison former reaction pathway, latter process appears less efficient prone side reactions. both cases, achiral enol enamine formed, dissociation catalyst statistically either stereoisomers substrate. Since only enantiomer (or diastereoisomer) processed, high enantioselectivity diastereoselectivity) results. Even though contra-thermodynamic process, described decoupling thermal usage loadings vary between 2.5 10 mol % depending on specific mode action.

Language: Английский

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Deracemization of C(sp³)–H Arylated Carbonyl Compounds via Asymmetric Ion-Pairing Photoredox Catalysis

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: April 17, 2025

Deracemization of C(sp3)-H arylated carbonyl compounds faces limitations in terms substrate scope. Through the photoactivation aryl group and stereocontrol generated arene radical cation via asymmetric ion-pairing catalysis, we are able to achieve deracemization at both enolizable unenolizable stereocenters. A diverse range α-, β-, γ-aryl ketones esters, including natural products medicinal derivatives, can be effectively converted into their enantiomers with high enantioselectivity. Mechanistic investigations through combined experimental computational studies suggest that reaction involves single-electron oxidation electron-rich groups, followed by a kinetic resolution resulting intermediates chiral phosphate anion. Deprotonation is identified as stereodetermining step, while stereoselective back electron transfer triplet-state quenching 3 Mes-Acr1+* may also affect enantioselectivity photostationary state.

Language: Английский

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Catalytic Enantioselective Hydrogen Atom Abstraction Enables the Asymmetric Oxidation of Meso Diols

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 26, 2024

Desymmetrization of meso diols is an important strategy for the synthesis chiral oxygen-containing building blocks. Oxidative desymmetrization subclass, but existing methods are often constrained by need activated alcohol substrates. We disclose a conceptually distinct toward oxidative diol that enabled catalytic enantioselective hydrogen atom abstraction. Following single electron oxidation cinchona alkaloid-derived catalyst, enantiodetermining abstraction generates desymmetrized ketyl radical intermediate which reacts with either DIAD or O2 before in situ elimination to form valuable hydroxyketone products. A range cyclic and acyclic competent, defining absolute configuration up four stereocenters operation. As well as providing rapid access complex hydroxyketones, this work emphasizes broad synthetic potential harnessing manner.

Language: Английский

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Visible light-induced 3H-indole hydrogenation using tetramethylethene as an inert hydrogen source

Tetrahedron Letters, Journal Year: 2024, Volume and Issue: 140, P. 155017 - 155017

Published: March 20, 2024

Language: Английский

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Katalytische photochemische Deracemisierung über kurzlebige Intermediate

Angewandte Chemie, Journal Year: 2023, Volume and Issue: 135(50)

Published: July 10, 2023

Abstract Bei Bestrahlung können Racemate in Gegenwart eines geeigneten chiralen Katalysators enantiomerenreine Verbindungen mit gleicher Struktur umgewandelt werden. Dieser Prozess wird photochemische Deracemisierung genannt und beinhaltet die Bildung kurzlebiger Intermediate. Das Eröffnen unterschiedlicher Reaktionswege für Vorwärtsreaktion zum Intermediat sowie Rückbildung des Moleküls ermöglicht diesen entropisch ungünstigen Prozess. Seit der Entdeckung ersten photochemischen im Jahr 2018 hat sich das Forschungsgebiet rapide entwickelt. Die vorliegende Übersicht diesem Bereich durchgeführte Forschung diskutiert aktuelle Entwicklungen. Sie wurde unterteilt gemäß Art Differenzierung den jeweiligen Substratklassen. Der Schwerpunkt dieser liegt auf Substratpalette einzelner Reaktionen einer Diskussion mechanistischen Details, vorgestellten Reaktion zugrunde liegen.

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