Photochemical Deracemization at sp 3 -Hybridized Carbon Centers via a Reversible Hydrogen Atom Transfer

A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80-99% ). The reaction is catalyzed by a chiral diarylketone which displays a two-point hydrogen bonding site. Mechanistic evidence (DFT calculations, radical clock exp...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2021-12, Vol.143 (50), p.21241-21245
Main Authors: Großkopf, Johannes, Plaza, Manuel, Seitz, Antonia, Breitenlechner, Stefan, Storch, Golo, Bach, Thorsten
Format: Article
Language:English
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Summary:A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80-99% ). The reaction is catalyzed by a chiral diarylketone which displays a two-point hydrogen bonding site. Mechanistic evidence (DFT calculations, radical clock experiments, H/D labeling) suggests the reaction to occur by selective hydrogen atom transfer (HAT). Upon hydrogen binding, one substrate enantiomer displays the hydrogen atom at the stereogenic center to the photoexcited catalyst allowing for a HAT from the substrate and eventually for its conversion into the product enantiomer. The product enantiomer is not processed by the catalyst and is thus enriched in the photostationary state.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.1c11266