The importance of 1,5-oxygen···chalcogen interactions in enantioselective isochalcogenourea catalysis
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The importance of 1,5-O···chalcogen (Ch) interactions in isochalcogenourea catalysis (Ch = O, S, Se) is investigated. Conformational analyses of N-acyl isochalcogenouronium species and comparison with kinetic data demonstrate the significance of 1,5-O···Ch interactions in enantioselective catalysis. Importantly, the selenium analogue demonstrates enhanced rate and selectivity profiles across a range of reaction processes including nitronate conjugate addition and formal [4+2] cycloadditions. A gram-scale synthesis of the most active selenium analogue was developed using a previously unreported seleno-Hugerschoff reaction, allowing the challenging kinetic resolutions of tertiary alcohols to be performed at 500 ppm catalyst loading. Density Functional Theory (DFT) and natural bond orbital (NBO) calculations support the role of orbital delocalization (occurring by intramolecular chalcogen bonding) in determining the conformation, equilibrium population, and reactivity of N-acylated intermediates.
Young , C M , Elmi , A , Pascoe , D J , Morris , R K , McLaughlin , C , Woods , A , Frost , A , De La Houpliere , A , Ling , K B , Smith , T K , Slawin , A M Z , Willoughby , P H , Cockroft , S L & Smith , A D 2020 , ' The importance of 1,5-oxygen···chalcogen interactions in enantioselective isochalcogenourea catalysis ' , Angewandte Chemie International Edition , vol. 59 , no. 9 , pp. 3705-3710 . https://doi.org/10.1002/anie.201914421
Angewandte Chemie International Edition
Copyright © 2019 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1002/anie.201914421
DescriptionSyngenta (Case Award to DJP) and a Philip Leverhulme Prize for funding (SLC, AE). RKM and PHW are grateful to the American Chemical Society Petroleum Research Fund and National Science Foundation (NSF-MRI: CHE-1429616).
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