Evidence for involvement of cationic intermediate in epoxidation of chiral allylic alcohols and unfunctionalised alkenes catalysed by MnIII(quinazolinone) complexes

Çakıcı M., Kılıç H., Ulukanlı S., Ekinci D.

Tetrahedron, vol.74, no.1, pp.49-57, 2018 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 74 Issue: 1
  • Publication Date: 2018
  • Doi Number: 10.1016/j.tet.2017.11.034
  • Journal Name: Tetrahedron
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.49-57
  • Ataturk University Affiliated: Yes

Abstract

A pair of Mn-III(quinazolinone) complexes was prepared and evaluated in the catalytic epoxidation of the chiral allylic alcohols and unfunctionalised alkenes with iodosylbenzene. Epoxidation of chiral allylic alcohols with 1,3-allylic strain proceeded chemo- and diastereoselectively to give threo-epoxy alcohol (up to 99% d.r). Epoxidation of unfunctionalised alkenes by the proposed catalyst system proceeded nonselectively, as evidenced by the formation of isomerization and rearrangement products in the epoxidation of (Z)-stilbene. A three-step pathway involving a cationic intermediate is proposed for the formation of isomerization and rearrangement products. The fact that only products resulting from the cationic intermediate were detected in the oxidation of a mechanistic probe, (2-methoxy-3-vinylcyclopropyl)benzene, with Mn-III(quinazolinone) and PhIO substantiated the cationic oxygen transfer mechanism. (C) 2017 Elsevier Ltd. All rights reserved.