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Related Experiment Videos

8-phenyl-10,10a-dihydropyrido

Marx1, Eberbach

  • 1Institut fur Organische Chemie und Biochemie der Universitat Freiburg, Germany.

Chemistry (Weinheim an Der Bergstrasse, Germany)
|July 14, 2000
PubMed
Summary

Treatment of pyridinium bromides yields dihydropyridoazepines via ylide intermediates. Quantum mechanical calculations explain the observed 8pi-electrocyclization selectivity in this heterocyclic synthesis.

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Dihydro

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Area of Science:

  • Organic Chemistry
  • Heterocyclic Chemistry
  • Computational Chemistry

Background:

  • Pyridinium salts are versatile precursors in organic synthesis.
  • Electrocyclization reactions are key transformations in forming cyclic systems.
  • Understanding reaction mechanisms and selectivity is crucial for synthetic strategy.

Purpose of the Study:

  • To investigate the reaction of pyridinium bromides with base.
  • To elucidate the mechanism and stereoselectivity of the observed cyclization.
  • To provide a theoretical basis for the reaction's outcome using computational methods.

Main Methods:

  • Base-induced reaction of pyridinium bromides (11a-e).
  • Isolation and characterization of monomolecular products (14a-e).
  • Quantum mechanical calculations to analyze the electrocyclization pathway.

Main Results:

  • Formation of dihydropyridoazepines (14a-e) as the sole monomolecular products.
  • Identification of ylide intermediates (12) preceding cyclization.
  • Experimental evidence confirmed 8pi-electrocyclization, with no 6pi-cyclization products detected.

Conclusions:

  • The base treatment of pyridinium bromides selectively yields dihydropyridoazepines through an 8pi-electrocyclization pathway.
  • Quantum mechanical calculations successfully rationalize the observed periselective electrocyclization.
  • The study clarifies the reaction mechanism, highlighting the importance of ylide intermediates in forming seven-membered heterocyclic rings.

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