Visible light photocatalysis – from racemic to asymmetric activation strategies

Chemical Communications, Journal Year: 2020, Volume and Issue: 56(76), P. 11169 - 11190

Published: Jan. 1, 2020

The most significant contributions towards enantioselective photocatalysis have been described with a special emphasis on the various activation strategies.

Language: Английский

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Catalytic Asymmetric Reductive Azaarylation of Olefins via Enantioselective Radical Coupling

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(17), P. 7805 - 7814

Published: April 26, 2022

Visible-light-driven photocatalytic reductive azaarylation has been widely used to construct the important imine-containing azaarene derivatives. In addition direct use of various commercially available cyanoazaarenes as feedstocks, synthetic advantages include precise regioselectivity, high efficiency, mild reaction conditions, and good functional group tolerance. However, although many efficient methods have established, example an enantioselective manner is still unmet, which most likely can be ascribed highly reactive radical coupling key step forming stereocenters. Exploring feasibility enantiocontrol thus constitutes attractive but challenging task. Here, we demonstrate that chiral hydrogen-bonding/photosensitizer catalysis a viable platform it enables realization first manifold. A variety acyclic cyclic enones partners are compatible with dual catalyst system, leading wide array valuable enantioenriched variants yields ees. Regulating types catalysts represents one manners success, in several readily accessible Cinchona alkaloid-derived bifunctional introduced asymmetric photochemical reactions.

Language: Английский

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Asymmetric Hydroaminoalkylation of Alkenylazaarenes via Cooperative Photoredox and Chiral Hydrogen‐Bonding Catalysis

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(10)

Published: Jan. 10, 2022

Chiral hydrogen-bonding (H-bonding) catalytic asymmetric conjugate addition to activated olefins has been widely used access enantioenriched molecules containing stereocenters at the β-position of olefin activating groups. Herein, we report first highly enantioselective radical-based manifold. Under a dual organocatalyst system involving chiral phosphoric acid and DPZ as photoredox sensitizer, transformations N-arylglycines, in which aryls with CF3 substituents are introduced, alkenyl azaarenes afforded valuable hydroaminoalkylation adducts satisfactory results. In diversity azaarenes, method can be construct aryl-, alkyl- silyl-substituted stereocenter. Control experiments density functional theory calculations were performed elucidate plausible reaction mechanism origin stereoselectivity, wherein nonclassical H-bonding interactions found assist catalysts offering sufficient enantiocontrol.

Language: Английский

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Asymmetric Photocatalytic C(sp³)–H Bond Addition to α-Substituted Acrylates

Organic Letters, Journal Year: 2021, Volume and Issue: 23(8), P. 3157 - 3161

Published: March 29, 2021

Asymmetric functionalization of inert C(sp3)-H bonds is a straightforward approach to realize versatile bond-forming events, allowing the precise assembly molecular complexity with minimal functional manipulations. Here, we describe an asymmetric photocatalytic bond addition α-substituted acrylates by using tetrabutylammonium decatungstate (TBADT) as hydrogen atom transfer (HAT) photocatalyst and chiral phosphoric acid proton-transfer shuttle. This protocol supposed occur via radical/ionic relay process, including TBADT-mediated HAT cleave bond, 1,4-radical addition, back abstraction, enantioselective protonation. A variety C-H patterns are well tolerated enable rapid synthesis enantioenriched α-stereogenic esters from simple raw materials.

Language: Английский

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Deracemization through Sequential Photoredox‐Neutral and Chiral Brønsted Acid Catalysis

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(49)

Published: Oct. 17, 2022

Abstract Catalytic deracemization is an ideal synthetic strategy due to its formally perfect atom utilization. Asymmetric photocatalysis has been appreciated as a promising tool accomplish this attractive reaction pattern in economical fashion, but it remains underdeveloped. Here, we report new platform based on photoredox‐neutral catalysis, allowing efficient and modular optical enrichment of α‐amino esters other valuable analogues. Two single‐electron transfer processes between the photocatalyst substrates serve provide key prochiral intermediates, chiral Brønsted acid catalyst mediates enantioselective protonation reconstitute stereogenic C−H bond. The efficiency determined by enantiofacial differentiation effect during stereocentre‐forming step.

Language: Английский

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Remote stereocontrol with azaarenes via enzymatic hydrogen atom transfer

Nature Chemistry, Journal Year: 2023, Volume and Issue: 16(2), P. 277 - 284

Published: Nov. 16, 2023

Language: Английский

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Asymmetric Dearomatization of Indoles with Azodicarboxylates via Cascade Electrophilic Amination/Aza-Prins Cyclization/Phenonium-like Rearrangement

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(21), P. 11745 - 11753

Published: May 19, 2023

Herein, we report a highly efficient synthesis of enantioenriched aza-[3.3.1]-bicyclic enamines and ketones, class structural cores in many natural products, via asymmetric dearomatization indoles with azodicarboxylates. The reaction is initiated by electrophilic amination followed aza-Prins cyclization/phenonium-like rearrangement. A newly developed fluorine-containing chiral phosphoric acid displays excellent activity promoting this cascade reaction. absence or presence water as the additive directs pathway toward either enamine ketone products high yields (up to 93%) enantiopurity 98% ee). Comprehensive density functional theory (DFT) calculations reveal energy profile origins enantioselectivity water-induced chemoselectivity.

Language: Английский

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Enantioselective Chemodivergent Three-Component Radical Tandem Reactions through Asymmetric Photoredox Catalysis

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(36), P. 20141 - 20148

Published: Aug. 28, 2023

Chemodivergent synthesis has been achieved in asymmetric photocatalysis. Under a dual catalyst system consisting of chiral phosphoric acid and DPZ as photosensitizer, different inorganic bases enabled the formation two sets valuable products from three-component radical tandem transformations 2-bromo-1-arylenthan-1-ones, styrenes, quinoxalin-2(1H)-ones. The key to success was distinct pKa environment, which radicals that formed on quinoxalin-2(1H)-one rings after addition processes underwent either single-electron oxidation or reduction. In addition, this work represents first use quinoxalin-2(1H)-ones photoredox catalysis.

Language: Английский

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Catalytic Asymmetric Redox‐Neutral [3+2] Photocycloadditions of Cyclopropyl Ketones with Vinylazaarenes Enabled by Consecutive Photoinduced Electron Transfer

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(30)

Published: April 30, 2024

Abstract Consecutive photoinduced electron transfer (ConPET) is a powerful and atom‐economical protocol to overcome the limitations of intrinsic redox potential visible light‐absorbing photosensitizers, thereby considerably improving substrate reaction types. Likely because such an exothermic single‐electron (SET) process usually does not require aid chiral catalysts, resulting in inevitable racemic background reaction, notably, no enantioselective manifolds have been reported. Herein, we report on viability cooperative ConPET hydrogen‐bonding catalysis for [3+2] photocycloaddition cyclopropyl ketones with vinylazaarenes. In addition enabling first use olefins that preferentially interact this platform paves way efficient synthesis pharmaceutically synthetically important cyclopentyl functionalized by azaarenes high yields, ees dr. The robust capacity method can be further highlighted low loading catalyst (1.0 mol %), good compatibility both 2‐azaarene 3‐pyridine‐based olefins, successful concurrent construction three stereocenters cyclopentane rings involving elusive but all‐carbon quaternary.

Language: Английский

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Radical Cross Coupling and Enantioselective Protonation through Asymmetric Photoredox Catalysis

Advanced Science, Journal Year: 2024, Volume and Issue: 11(12)

Published: Jan. 17, 2024

Abstract An unprecedented enantioselective protonation reaction enabled by photoredox catalytic radical coupling is developed. Under cooperative dicynopyrazine‐derived chromophore (DPZ) as a photosensitizer and chiral phosphoric acid catalyst, Hantzsch ester sacrificial reductant, the transformations between α‐substituted enones cyanoazaarenes or 2‐(chloromethyl)azaaren‐1‐iums can proceed tandem reduction, coupling, process efficiently. Two classes of pharmaceutically important enantioenriched azaarene variants, which contain synthetically versatile ketone‐substituted tertiary carbon stereocenter at β ‐ γ ‐position azaarenes, are synthesized with high yields ees.

Language: Английский

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