Kinetic resolution of unsaturated amides in a chlorocyclization reaction: concomitant enantiomer differentiation and face selective alkene chlorination by a single catalyst

J Am Chem Soc. 2013 Oct 2;135(39):14806-13. doi: 10.1021/ja407241d. Epub 2013 Sep 17.

Abstract

The first example of a kinetic resolution via chlorofunctionalization of olefins is reported. The enantiomers of racemic unsaturated amides were found to have different hydrogen-bonding affinities for chiral Lewis bases in numerous solvents. This interaction was exploited in developing a kinetic resolution of racemic unsaturated amides via halocyclization. The same catalyst serves to both "sense chirality" in the substrate as well as mediate a highly face-selective chlorine delivery onto the olefin functionality, resulting in stereotriad products in up to 99:1 dr and up to 98.5:1.5 er. The selectivity factors were typically greater than 50 to allow for the simultaneous synthesis of both the products and unreacted substrates in highly enantioenriched form at yields approaching 50%. The reaction employs catalytic amounts (≤0.50 mol %) of a commercially available and recyclable organocatalyst.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alkenes / chemistry*
  • Amides / chemistry*
  • Catalysis
  • Cyclization
  • Halogenation
  • Kinetics
  • Stereoisomerism

Substances

  • Alkenes
  • Amides