Thermolyses of O-Phenyl Oxime Ethers. A New Source of Iminyl Radicals and a New Source of Aryloxyl Radicals

Par Conseil national de recherches du Canada

DOI	Trouver le DOI : https://doi.org/10.1021/jo049927y
Auteur	Rechercher : Blake, J.A.¹; Rechercher : Pratt, D.A.; Rechercher : Lin, S.¹; Rechercher : Walton, J.C.; Rechercher : Mulder, P.; Rechercher : Ingold, K. U.¹
Affiliation	Conseil national de recherches du Canada
Format	Texte, Article
Sujet	Dissociation; Enthalpy; Free radicals; Reaction kinetics; Synthesis (chemical); Cyclization; Hyperconjugation; Thermolyses; Ethers; ether derivative; imine; iminyl radical; n phenoxybenzimidic acid phenyl ether; o phenyl oxime ether derivative; oxyl radical; phenoxybenzamine; radical; unclassified drug; beta scission; binding competition; calculation; chemical analysis; chemical binding; chemical reaction kinetics; conjugation; cyclization; density functional theory; dissociation; enthalpy; product recovery; reaction analysis; room temperature; synthesis; temperature sensitivity; thermal analysis; thermolysis
Résumé	Six O-phenyl ketoxime ethers, RR′C=NOPh 1-6, with RR′= diaryl, dialkyl, and arylalkyl, together with N-phenoxybenzimidic acid phenyl ether, PhO(Ph)C=NOPh, 7, have been shown to thermolyze at moderate temperatures with "clean" N-O bond homolyses to yield iminyl and phenoxyl radicals, RR′C=N. and PhO.. Since 1-6 can be synthesized at room temperature, these compounds provide a new and potentially useful source of iminyls for syntheses. The iminyl from 7 undergoes a competition between β-scission, to PhCN and PhO., and cyclization to an oxazole. Rate constants, 106 k/s-1, at 90 °C for 1-6 range from 4.2 (RR′ = 9-fluorenyl) to 180 (RR′ = 9-bicyclononanyl), and that for 7 is 0.61. The estimated activation enthalpies for N-O bond scission are in satisfactory agreement with the results of DFT calculations of N-O bond dissociation enthalpies, BDEs, and represent the first thermochemical data for any reaction yielding iminyl radicals. The small range in k (N-O homolyses) is consistent with the known σ structure of these radicals, and the variations in k and N-O BDEs with changes in RR′ are rationalized in terms of iminyl radical stabilization by hyperconjugation: RR′C=N . ↔ R.R′C≡N. Calculated N-H BDEs in the corresponding RR′C= NH are also presented.
Date de publication	2004
Dans	Journal of Organic Chemistry 69, nº 9 (2004) : 3112–3120.
Langue	anglais
Publications évaluées par des pairs	Oui
Numéro NPARC	21276655
Exporter la notice	Exporter en format RIS
Signaler une correction	Signaler une correction (s'ouvre dans un nouvel onglet)
Identificateur de l’enregistrement	217b530b-6469-4c68-9bab-3af48ea6c0e2
Enregistrement créé	2015-10-13
Enregistrement modifié	2020-04-17

Date de modification :: 2024-09-13