Ambident reactivity of acetyl- and formyl-stabilized phosphonium ylides

Show simple item record Byrne, Peter A. Karaghiosoff, Konstantin Mayr, Herbert 2019-04-04T09:03:39Z 2019-04-04T09:03:39Z 2016-07-08
dc.identifier.citation Byrne, P. A., Karaghiosoff, K. and Mayr, H. (2016) 'Ambident Reactivity of Acetyl- and Formyl-Stabilized Phosphonium Ylides', Journal of the American Chemical Society, 138(35), pp. 11272-11281. doi: 10.1021/jacs.6b06264 en
dc.identifier.volume 138 en
dc.identifier.startpage 11272 en
dc.identifier.endpage 11281 en
dc.identifier.issn 0002-7863
dc.identifier.doi 10.1021/jacs.6b06264 en
dc.description.abstract The kinetics and mechanism of the reactions of formyl-stabilized ylide Ph3P═CHCHO (1) and acetyl-stabilized ylide Ph3P═CHCOMe (2) with benzhydrylium ions (Ar2CH+, 3) were investigated by UV–vis and NMR spectroscopy. As ambident nucleophiles, ylides 1 and 2 can react at oxygen as well as at the α-carbon. For some reactions, it was possible to determine the second-order rate constant for O-attack as well as for C-attack and to derive the nucleophile-specific parameters N and sN according to the correlation lg k (20 °C) = sN(E + N) for both nucleophilic sites. Generally, O-attack of benzhydrylium ions is faster than C-attack. However, the initially formed benzhydryloxyvinylphosphonium ions can only be observed by NMR spectroscopy when benzhydryl cations with high Lewis acidity are employed. In other cases, rearrangement to the thermodynamically more stable products arising from C-attack occurs. The results derived from our investigations are employed to rationalize the behavior of ambident nucleophiles 1 and 2 in reactions with carbon-centered electrophiles in general. It is shown that the principle of hard and soft acids and bases (HSAB) and the related Klopman–Salem concept of charge and orbital control lead to incorrect predictions of regioselectivity. We also show that the rate of the Wittig reaction of ylide 2 with aldehyde 14 is significantly faster than the rate of either C- or O-attack calculated using lg k (20 °C) = sN(E + N), thus indicating that the oxaphosphetane is formed by a concerted [2 + 2] cycloaddition. en
dc.description.sponsorship Alexander von Humboldt-Stiftung (Humboldt foundation, Humboldt Research Fellowship for Postdoctoral Researchers); Deutsche Forschungsgemeinschaft (SFB 749, Project B1) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher American Chemical Society, ACS en
dc.rights © 2016 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of the American Chemical Society, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see en
dc.subject Phosphonium ylide en
dc.subject Nucleophilicity en
dc.subject Reactivity en
dc.subject Ambident nucleophile en
dc.subject Marcus theory en
dc.title Ambident reactivity of acetyl- and formyl-stabilized phosphonium ylides en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Peter Byrne, Chemistry, University College Cork, Cork, Ireland. +353-21-490-3000 Email: en
dc.internal.availability Full text available en 2019-03-26T17:12:07Z
dc.description.version Accepted Version en
dc.internal.rssid 383418210
dc.contributor.funder Alexander von Humboldt-Stiftung en
dc.contributor.funder Deutsche Forschungsgemeinschaft en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Journal of the American Chemical Society en
dc.internal.copyrightchecked No
dc.internal.licenseacceptance Yes en
dc.internal.IRISemailaddress en
dc.identifier.eissn 1520-5126

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