Formation of new pyridyl substituted enamines. Observation of a diaza-Cope rearrangement

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Abstract

Some 2-arylthiopyridinium imides when reacted with dimethyl acetylene dicarboxylate exhibited ambident behaviour: either a 1,3-dipolar cyclization occurred followed by a ring transformation to yield pyrrolopyridines or 5-pyridyl substituted enamines were formed in a different route. Mechanistic considerations revealed that this latter unusual transformation is initiated by a Michael addition of the imide nitrogen atom of the starting pyridinium compound on the reagent, which is followed by a [3,3]-sigmatropic ('diaza-Cope') rearrangement. Ring opening of the pyrrolopyridine compounds by a base also yielded pyridylenamines, which proved to be positional isomers of the sigmatropic rearrangement products. The new pyridyl derivatives seem to be valuable compounds for further transformations. Thus, they can undergo thermal electrocyclization to 7-azaindoles.

Original languageEnglish
Pages (from-to)10375-10380
Number of pages6
JournalTetrahedron
Volume64
Issue number45
DOIs
Publication statusPublished - Nov 3 2008

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Keywords

  • Cycloadditions
  • Diaza-Cope rearrangement
  • Electrocyclization
  • Mesomeric betaine
  • Michael-addition

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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