Download PDF
Synfacts 2017; 13(05): 0545
DOI: 10.1055/s-0036-1590234
Polymer-Supported Synthesis
© Georg Thieme Verlag Stuttgart · New York

Chiral Piperazines by Phosphoric Acid/Metal Nanoparticle Catalysis

Authors

    Contributor(s):

  • Yasuhiro Uozumi

  • Shun Ichii

Cheng H.-G. Miguélez J. Miyamura H. Yoo W.-J. Kobayashi S. * The University of Tokyo, Japan
Integration of Aerobic Oxidation and Intermolecular Asymmetric Aza-Friedel–Crafts Reactions with a Chiral Bifunctional Heterogeneous Catalyst.

Chem. Sci. 2017;
8: 1356-1359
CrossrefPubMedSearch in Google Scholar
Further Information

Publication History

Publication Date:
18 April 2017 (online)

 
 PDF Download Permissions and Reprints

Key words

gold catalysis - palladium catalysis - platinum catalysis - aza-Friedel–Crafts reaction - benzylic alcohols - aminoethylpyrroles

Significance

Chiral phosphoric acids immobilized on polymer/carbon black-entrapped Au/Pd or Au/Pt nanoparticles (1 and 2, respectively) were prepared according to eq. 1. Catalysts 1 and 2 promoted an aerobic oxidation of benzyl alcohols and subsequent asymmetric aza-Friedel–Crafts reaction with N-(2-aminoethyl)pyrroles in one pot to give the corresponding chiral piperazines in ≤91% yield and ≤95% ee (eq. 2).


Comment

Benzyl methyl sulfide prevents oxidation of the resulting piperazine products to their imine forms. In the sequential reactions of benzyl alcohol and [2-(1H-pyrrol-1-yl)ethyl]amine, catalyst 1 was recovered by filtration and reused five times without significant loss of its catalytic performance (first run: 92% yield, 89% ee, sixth run: 85% yield, 84% ee).





  Permissions and Reprints