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Reactions of the cumyloxyl and benzyloxyl radicals with tertiary amides. hydrogen abstraction selectivity and the role of specific substrate-radical hydrogen bonding

Par Conseil national de recherches du Canada

DOITrouver le DOI : https://doi.org/10.1021/jo400535u
AuteurRechercher : ; Rechercher : ; Rechercher : 1; Rechercher :
Affiliation
  1. Conseil national de recherches du Canada. Institut national de nanotechnologie
FormatTexte, Article
SujetHydrogen abstraction reaction; Hydrogen bond interaction; Intramolecular hydrogen; N ,N-Dimethylacetamide; N ,N-Dimethylformamide; Rate-limiting formation; Theoretical investigations; Time-resolved kinetic study; Amides; Functional groups; Hydrogen bonds; Organic solvents; Substrates; Abstracting; acetic acid derivative; aliphatic amine; amide; benzyloxyl radical; carbon; cumyloxyl radical; dimethyl sulfoxide; hydrogen; hydroxyl radical; n,n dimethylacetamide; n,n dimethylformamide; oxygen; tertiary amine; unclassified drug; calculation; chemical reaction kinetics; chemical structure; density functional theory; dissociation constant; enzyme specificity; hydrogen bond; mathematical computing; molecular interaction; phase transition; stereochemistry
Résumé
A time-resolved kinetic study in acetonitrile and a theoretical investigation of hydrogen abstraction reactions from N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) by the cumyloxyl (CumO•) and benzyloxyl (BnO•) radicals was carried out. CumO • reacts with both substrates by direct hydrogen abstraction. With DMF, abstraction occurs from the formyl and N-methyl C-H bonds, with the formyl being the preferred abstraction site, as indicated by the measured k H/kD ratios and by theory. With DMA, abstraction preferentially occurs from the N-methyl groups, whereas abstraction from the acetyl group represents a minor pathway, in line with the computed C-H BDEs and the kH/kD ratios. The reactions of BnO• with both substrates were best described by the rate-limiting formation of hydrogen-bonded prereaction complexes between the BnO• α-C-H and the amide oxygen, followed by intramolecular hydrogen abstraction. This mechanism is consistent with the very large increases in reactivity measured on going from CumO• to BnO• and with the observation of kH/kD ratios close to unity in the reactions of BnO•. Our modeling supports the different mechanisms proposed for the reactions of CumO• and BnO • and the importance of specific substrate/radical hydrogen bond interactions, moreover providing information on the hydrogen abstraction selectivity. © 2013 American Chemical Society.
Date de publication
Dans
  • Journal of Organic Chemistry 78, nº 12 (2013) : 5909–5917.
Langueanglais
Publications évaluées par des pairsOui
Numéro NPARC21269778
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Identificateur de l’enregistremente9fe8d3f-7635-41cb-921e-9cd360c3570c
Enregistrement créé2013-12-13
Enregistrement modifié2020-04-22
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