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Intramolecular homolytic substitution of sulfinates and sulfinamides--a computational study.

Authors
  • Kyne, Sara H
  • Aitken, Heather M
  • Schiesser, Carl H
  • Lacôte, Emmanuel
  • Malacria, Max
  • Ollivier, Cyril
  • Fensterbank, Louis
Type
Published Article
Journal
Organic & Biomolecular Chemistry
Publisher
The Royal Society of Chemistry
Publication Date
May 07, 2011
Volume
9
Issue
9
Pages
3331–3337
Identifiers
DOI: 10.1039/c1ob05043e
PMID: 21448476
Source
Medline
License
Unknown

Abstract

Ab initio and density functional theory (DFT) calculations predict that intramolecular homolytic substitution by alkyl radicals at the sulfur atom in sulfinates proceeds through a smooth transition state in which the attacking and leaving radicals adopt a near collinear arrangement. When forming a five-membered ring and the leaving radical is methyl, G3(MP2)-RAD//ROBHandHLYP/6-311++G(d,p) calculations predict that this reaction proceeds with an activation energy (ΔE(1)(‡)) of 43.2 kJ mol(-1). ROBHandHLYP/6-311++G(d,p) calculations suggest that the formation of five-membered rings through intramolecular homolytic substitution by aryl radicals at the sulfur atom in sulfinates and sulfinamides, with expulsion of phenyl radicals, proceeds with the involvement of hypervalent intermediates. These intermediates further dissociate to the observed products, with overall energy barriers of 45-68 kJ mol(-1), depending on the system of interest. In each case, homolytic addition to the phenyl group competes with substitution, with calculated barriers of 51-78 kJ mol(-1). This computational study complements and provides insight into previous experimental observations.

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