Asymmetric ortho-lithiation of 1,n-dioxa[n]paracyclophane derivatives for the generation of planar chirality

Kazumasa Kanda, Risa Hamanaka, Kohei Endo, Takanori Shibata

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The asymmetric induction of planar chirality in 1,n-dioxa[n]paracyclophane derivatives via asymmetric ortho-lithiation is described. Enantioselective ortho-lithiation of unflippable 1,n-dioxa[n]paracyclophanes (n≤11) using sec-BuLi-(-)-sparteine at -78 °C and subsequent treatment with electrophiles gave the corresponding planar-chiral monosubstituted paracyclophanes with excellent ee. Further lithiation of these compounds and treatment with electrophiles gave planar-chiral paracyclophanes with two different substituents. Dilithiation of unflippable 1,n-dioxa[n]paracyclophanes gave the corresponding C 2-symmetrical disubstituted products with almost perfect ee. In the case of flippable 1,n-dioxa[n]paracyclophanes (n≥12), a stepwise reaction was required for the highly enantioselective formation of disubstituted products.

Original languageEnglish
Pages (from-to)1407-1416
Number of pages10
JournalTetrahedron
Volume68
Issue number5
DOIs
Publication statusPublished - 2012 Feb 4

Keywords

  • Enantioselective
  • Paracyclophane
  • Planar chirality
  • ortho-Lithiation

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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