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

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Title
Enantioselective Intermolecular Excited-State Photoreactions Using a Chiral Ir Triplet Sensitizer: Separating Association from Energy Transfer in Asymmetric Photocatalysis
Author(s)
Jian Zheng; Wesley B. Swords; Hoimin Jung; Jesse B. Kidd; Gerald J. Meyer; Mu-Hyun Baik; Tehshik P. Yoon
Publication Date
2019-08
Journal
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, v.141, no.34, pp.13625 - 13634
Publisher
AMER CHEMICAL SOC
Abstract
Copyright © 2019 American Chemical Society.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
URI
https://pr.ibs.re.kr/handle/8788114/6444
ISSN
0002-7863
Appears in Collections:
Center for Catalytic Hydrocarbon Functionalizations(분자활성 촉매반응 연구단) > Journal Papers (저널논문)
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