2008/10/21 by Gregory L. Hamilton, Toshio Kanai, F. Dean Toste · 2 citations
Chemistry · #Asymmetric Hydrogenation and Catalysis #Asymmetric Synthesis and Catalysis #Synthesis and Catalytic Reactions
paper · doi:10.1021/ja806431d
openalex publication_date 2008/10/21 · openalex created_date 2016/06/24 · openalex updated_date 2026/06/23
Reactions proceeding through cationic intermediates that lack a Lewis or Brønsted 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 beta-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.