The Atroposelective Iodination of 2-Amino-6-arylpyridines Catalyzed by Chiral Disulfonimides Actually Proceeds via Brønsted Base Catalysis: A Combined Experimental, Computational, and Machine-Learning Study.

Journal: Journal of the American Chemical Society
Published Date:

Abstract

A thorough mechanistic investigation into the disulfonimide (DSI)-catalyzed atroposelective iodination of 2-amino-6-arylpyridines with N-iodosuccinimide is described. While initially hypothesized to proceed via Brønsted-acid catalysis through activation of NIS, experimental evidence led us to reconsider the possible function of the DSI catalyst. We now propose an unprecedented mechanism in which the conjugate base of the DSI functions instead as a Brønsted-base, with the rate- and stereodetermining step involving an enantioselective deprotonation of a Wheland intermediate. The experimental data was used to initiate a DFT exploration of the reaction mechanism, which, after thorough analysis of the transition state structures and reaction coordinate, confirmed our revised hypothesis. The unique structural features of the highest-performing catalyst were explored further with a chemoinformatics-based workflow, leading to a detailed elucidation of those factors contributing to the origin of enantioselection.

Authors

  • Karnjit S Parmar
    Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave, Urbana, Illinois 61801, United States.
  • Seth Bawel
    Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave, Urbana, Illinois 61801, United States.
  • Mihai V Popescu
    Department of Chemistry, Colorado State University Fort Collins CO 80523 USA [email protected].
  • Binh Khanh Mai
    Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
  • Jacob C Timmerman
    Department of Synthetic Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States.
  • Bilal Altundas
    Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave, Urbana, Illinois 61801, United States.
  • Robert S Paton
    Department of Chemistry, Colorado State University Fort Collins CO 80523 USA [email protected].
  • Scott E Denmark
    Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States.

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