Chiral 2-pyridyl alcoholate copper complexes: Crystal structures of [bis(2-pyridyl alcoholate)copper(II)] and the use of [(2-pyridyl alcoholate)copper(II)]+and [(2-pyridyl alcoholate)copper(I)] in asymmetric cyclopropanation of styene and allylic oxidation of cyclohexene

Wing Sze Lee, Hon Kit Leung, Leung Shi Cheng, Lai Yuen Ng, Chi Sing Lee, Ka Hung Huang, Wing Tak Wong, Hoi Lun Kwong

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9 Citations (Scopus)

Abstract

Chiral N,O pyridine alcohols HL were used to form complexes with copper(II) ions. Three complexes, with formula [Cu(L)2], were isolated. Two crystal structures are described. Copper complexes formed in situ were found to be active catalysts for asymmetric catalysis. Chiral N,O pyridine alcohols HL1-HL6were used to form complexes with copper(II) ions. Ligands HL1and HL2formed complexes with copper(II) ions when Cu(OAc)2and HL were refluxed in methanol/ethanol mixture. Ligand HL3formed a complex with copper(II) when deprotonated with NaH and stirred in a Cu(II) acetate THF solution. Ligands HL4-HL6did not form complexes with copper(II) under similar conditions. Two complexes, [Cu(L1)2] and [Cu(L2)2], were isolated as single crystals and characterized by X-ray crystallography. These complexes showed low catalytic activities in asymmetric reactions. However, they became active when reacted with triflic acid. Copper complexes, [Cu(L)] or [Cu(L)]+, formed in situ by reacting ligands HL with copper(I) or (II) ions, respectively, were also found to be active copper catalysts for asymmetric cyclopropanation of styrene with ethyl diazoacetate and allylic oxidation of cyclohexene with t-butylperoxybenzoate. Enantioselectivities up to 56% and 38% were obtained in asymmetric cyclopropanation of styrene and asymmetric allylic oxidation of cyclohexene, respectively.
Original languageEnglish
Pages (from-to)4389-4395
Number of pages7
JournalInorganica Chimica Acta
Volume357
Issue number15
DOIs
Publication statusPublished - 1 Dec 2004
Externally publishedYes

Keywords

  • Alcoholate
  • Asymmetric
  • Copper
  • Pyridyl

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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