Asymmetric catalysis of triplet-state photoreactions

Sherbrook, Evan M.

doi:10.1039/9781788013598-00432

Cited by 22 publications

(11 citation statements)

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“…Asymmetric catalysis has been a central theme in synthetic organic chemistry for many decades. However, enantioselective catalysis of photochemical reactions has only recently been proven to be feasible . The central challenges in asymmetric excited-state photochemistry derive from the existence of unimolecular relaxation pathways that provide a rapid mechanism for deactivation of the key reactive intermediates in photochemical reactions.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Intermolecular Excited-State Photoreactions Using a Chiral Ir Triplet Sensitizer: Separating Association from Energy Transfer in Asymmetric Photocatalysis

et al. 2019

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Enantioselective catalysis of excited-state photoreactions remains a substantial challenge in synthetic chemistry, and intermolecular photoreactions have proven especially difficult to conduct in a stereocontrolled fashion. Herein, we report a highly enantioselective intermolecular [2 + 2] cycloaddition of 3-alkoxyquinolones catalyzed by a chiral hydrogen-bonding iridium photosensitizer. Enantioselectivities as high as 99% ee were measured in reactions with a range of maleimides and other electron-deficient alkene reaction partners. An array of kinetic, spectroscopic, and computational studies supports a mechanism in which the photocatalyst and quinolone form a hydrogen-bonded complex to control selectivity, yet upon photoexcitation of this complex, energy transfer sensitization of maleimide is preferred. The sensitized maleimide then reacts with the hydrogen-bonded quinolone–photocatalyst complex to afford a highly enantioenriched cycloadduct. This finding contradicts a long-standing tenet of enantioselective photochemistry that held that stereoselective photoreactions require strong preassociation to the sensitized substrate in order to overcome the short lifetimes of electronically excited organic molecules. This system therefore suggests that a broader range of alternate design strategies for asymmetric photocatalysis might be possible.

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Section: Introductionmentioning

confidence: 99%

Enantioselective Intermolecular Excited-State Photoreactions Using a Chiral Ir Triplet Sensitizer: Separating Association from Energy Transfer in Asymmetric Photocatalysis

et al. 2019

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“…Light‐driven catalysis is a thriving field of research owing to the synthetic potential of this strategy in organic chemistry In efforts to design new catalytic systems, the combination of photochemistry and asymmetric catalysis has been emerging as a relevant and efficient strategy by which chirality can be introduced into molecular architectures . Within this context, the induction of chemical processes under light illumination is triggered either by photoinduced electron transfer or energy transfer.…”

Section: Introductionmentioning

confidence: 99%

Controlling Photooxygenation with a Bifunctional Quinine‐BODIPY Catalyst: towards Asymmetric Hydroxylation of β‐Dicarbonyl Compounds

et al. 2019

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We report herein a new catalytic strategy towards asymmetric photooxygenation of β‐dicarbonyl compounds. Our method is based on the synthesis of a bifunctional photosensitizer composed of a quinine organocatalyst grafted to an iodo‐BODIPY framework capable of generating singlet oxygen. The quinine moiety serves both to interact with the substrate for promoting photooxygenation and to deactivate singlet oxygen in the absence of substrate. The bifunctional photosensitizer prepared was subsequently applied in the asymmetric oxygenation of a series of β‐dicarbonyl compounds under green light irradiation. Control experiments and kinetic analyses were carried out to shed the light on the mechanism.

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“… 9,10 Photochemical reactions have enabled numerous approaches to the enantioselective synthesis of bioactive and other useful compounds, 11 but control of enantioselectivity in the excited state continues to pose a challenge. 12 Recent progress in asymmetric photochemical reactions has mainly focused on [2 + 2] cycloadditions and [1,3]-migration reactions; 13 much rarer are enantioselective [1,7]-sigmatropic rearrangements. 14 …”

Section: Introductionmentioning

confidence: 99%

Enantioselective one-carbon expansion of aromatic rings by simultaneous formation and chromoselective irradiation of a transient coloured enolate

et al. 2022

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Asymmetric catalysis of triplet-state photoreactions

Cited by 22 publications

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Enantioselective Intermolecular Excited-State Photoreactions Using a Chiral Ir Triplet Sensitizer: Separating Association from Energy Transfer in Asymmetric Photocatalysis

Enantioselective Intermolecular Excited-State Photoreactions Using a Chiral Ir Triplet Sensitizer: Separating Association from Energy Transfer in Asymmetric Photocatalysis

Controlling Photooxygenation with a Bifunctional Quinine‐BODIPY Catalyst: towards Asymmetric Hydroxylation of β‐Dicarbonyl Compounds

Enantioselective one-carbon expansion of aromatic rings by simultaneous formation and chromoselective irradiation of a transient coloured enolate

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