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Detection of reactive tetrahedral intermediates in a deep cavitand with an introverted functionality

Academic Article
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Overview

authors

  • Hooley, R. J.
  • Iwasawa, T.
  • Rebek Jr., Julius

publication date

  • December 2007

journal

  • Journal of the American Chemical Society  Journal

abstract

  • Labile hemiaminal intermediates are stabilized by binding in a deep cavitand with an introverted aldehyde functionality. The aldehyde is attached to the cavitand via an anthracene spacer that rotates rapidly about the cavitand rim. The half-lives of these hemiaminals vary from 30 min to over 100 h at ambient temperature, due to hydrogen bonding with the organized peptide-like framework at the cavitand rim. The intermediates are sufficiently long-lived to allow study by 2D NMR techniques requiring many hours of acquisition time. Mechanistic analysis of the dehydration step shows first-order kinetics. The analogous "extroverted" reaction was also performed, where the addition took place outside the cavitand, displaying standard steady-state kinetics; no hemiaminal was observed. The cavitand shows strong selectivity based not on binding affinity but upon the rate of the product-forming step. A 10:1 ratio of product imines was obtained, while the initial binding ratio was 1:1. The cavitand acts as a mimic of enzymes in that it uses weak binding forces to stabilize reactive intermediates and isolates them from the medium. The synthetic environment allows direct detection and analysis of the intermediates, as opposed to natural systems that must be analyzed indirectly.

subject areas

  • Aldehydes
  • Amines
  • Anthracenes
  • Ethers, Cyclic
  • Hydrogen Bonding
  • Imines
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Molecular Conformation
  • Resorcinols
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Identity

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/ja0759343

PubMed ID

  • 18004856
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Additional Document Info

start page

  • 15330

end page

  • 15339

volume

  • 129

issue

  • 49

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