Synthesis and stereochemistry of 4-arylimino-1,3-oxazino- and 1,3-thiazino[4,3,a]isoquinolines

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Thioureas 2-5 were prepared from homocalycotomine and isocyanates. When 2 and 3 were treated with methyl iodide and then with alkaline, 9,10-dimethoxy-4-arylimino-1,6,7,11b-tetrahydro-2H,4H-1,3-oxazino[4,3-a] isoquinoline, 6 and 7 were formed. The corresponding 9,10-dimethoxy-4-arylimino- 1,6,7,11b-tetrahydro-2H,4H-1,3-thiazino [4,3-a]isoquinolines 8 and 9 were synthesized from 4 and 5 treatment with hydrogen chloride. The predominant conformations and the conformational equilibria were studied by means of NMR spectroscopy and molecular modelling calculations. The 1,3-X,N heterocyclic ring attains a flattened twist conformation, due to the orbital interaction between the bridgehead nitrogen lone pair and the C=N double bond.

Original languageEnglish
Pages (from-to)33-39
Number of pages7
Issue number3
Publication statusPublished - Dec 1 2001



  • Isocyanate
  • Isoquinoline
  • Oxazine
  • Stereochemistry
  • Synthesis

ASJC Scopus subject areas

  • Organic Chemistry

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