Highly regioselective anaerobic photocyclization of 3-styrylpyridines

F. D. Lewis*, R. S. Kalgutkar, J. S. Yang

*Corresponding author for this work

Research output: Contribution to journalArticle

50 Scopus citations

Abstract

The photochemical behavior of the cis isomers of the three isomeric styrylpyridines and two (aminostyryl)pyridines has been investigated under aerobic and anaerobic conditions. Both 3-styrylpyridine and its 3′-amino derivative undergo highly regioselective formation of 2-azaphenanthrene products under anaerobic conditions. In the presence of oxygen, mixtures of 4- and 2-azaphenanthrene products are obtained. The formation of 2-azaphenanthrenes in the absence of oxygen is attributed to conversion of the 4a,4b-dihydroazaphenanthrene primary photoproduct to a 1,4-dihydropyridine intermediate by means of a formal 1,7-hydrogen shift. This intermediate is moderately stable in the absence of oxygen and has been characterized by comparison of its 1H NMR and electronic absorption spectra with calculated spectra. This intermediate is converted to the 2-azaphenanthrene in both the absence and presence of oxygen. The regioselectivity of photocyclization of 3-substituted stilbenes and related diarylethylenes is suggested to depend on the relative rate constants for ring opening and sigmatropic rearrangements of the dihydrophenanthrene intermediates as well as their rates of reaction with oxygen or other oxidants.

Original languageEnglish (US)
Pages (from-to)3878-3884
Number of pages7
JournalJournal of the American Chemical Society
Volume123
Issue number17
DOIs
StatePublished - Oct 8 2001

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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