Substituent effects in the ring-chain tautomerism of 4-aryl-1,3,4,6,7,11b- hexahydro-2H-pyrimido[6,1-a]isoquinolines

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9 Citations (Scopus)


By condensation of 1-(2′-aminoethyl)-1,2,3,4-tetrahydroisoquinoline derivatives with substituted benzaldehydes, 1,6-unsubstituted and diastereomers of 1-methyl- or 6-methyl-substituted 4-aryl-9,10-dimethoxy-1,3,4,6,7,11b- hexahydro-2H-pyrimido[6,1-a]isoquinolines were prepared. The ring-chain tautomeric equilibria of most of these compounds in CDCl3 at 300 K were found to be shifted nearly totally towards either the cyclic or the open tautomeric forms, while the (6R*,11bR*)-6-methyl substituted compounds proved to be three-component tautomeric mixtures, the equilibria of which could be characterized by a Hammett-type equation. The conformational equilibria of the cyclic forms turned out to be strongly influenced by the 1- and 6-methyl substituents and the configurations of the substituted carbons (C-1 or C-6 and C-4) relative to C-11b.

Original languageEnglish
Pages (from-to)5287-5295
Number of pages9
Issue number22
Publication statusPublished - May 30 2005


  • Conformation
  • Diamines
  • Hexahydropyrimidines
  • Isoquinolines
  • Ring-chain tautomerism

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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