249622-08-0Relevant articles and documents
Chiral anion-mediated asymmetric ring opening of meso-aziridinium and episulfonium ions
Hamilton, Gregory L.,Kanai, Toshio,Toste, F. Dean
, p. 14984 - 14986 (2008)
Reactions proceeding through cationic intermediates that lack a Lewis or Bronsted basic site present a challenge for traditional asymmetric catalysis based on chiral metals or organocatalysts. We present an enantioselective ring opening of tetrasubstituted meso-aziridinium ions with alcohol nucleophiles proceeding through a chiral ion pair with a binaphthol-phosphate anion. The reaction is initiated by silver-induced ring closure of β-chloroamines using the Ag salt of the chiral anion as in situ generated catalyst. Use of insoluble Ag2CO3 as silver source is essential to obtain high enantioselectivity; we believe the chiral phosphate acts as a chiral anion phase transfer catalyst to bring silver ion into the organic phase. The chiral anion concept can also be extended to the related asymmetric opening of meso-episulfonium ions generated by protonation of trichloroacetimidates vicinal to sulfides. Copyright