Syntheses and conformational analyses of new naphth[1,2-e][1,3]oxazino[3,2- c]quinazolin-13-ones

Renáta Csütörtöki, István Szatmári, Andreas Koch, Matthias Heydenreich, Erich Kleinpeter, Ferenc Fülöp

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The syntheses of naphth[1,2-e][1,3]oxazino[3,2-c]quinazolin-13-one derivatives (3a-f) were achieved by the solvent-free heating of benzyloxycarbonyl-protected intermediates (2a-f) with MeONa. For intermediates 2a-f, prepared by the reactions of substituted aminonaphthols with benzyl N-(2-formylphenyl)carbamate, not only the expected trans ring form B and chain form A 1, but also the rearranged chain form A 2 as a new tautomer were detected in DMSO at room temperature. The quantity of A 2 in the tautomeric mixture was changed with time. Conformational analyses of the target heterocycles 3a-f by NMR spectroscopy and accompanying theoretical calculations at the DFT level of theory revealed that the oxazine ring preferred a twisted chair conformation and the quinazolone ring was planar. Besides the conformations, both the configurations at C-7a and C-15 and the preferred rotamers of the 1-naphthyl substituent at C-15 were assigned, which allowed evaluation of the aryl substituent-dependent steric hindrance in this part of the molecules. Configurational assignments were corroborated by quantifying the ring current effect of 15-aryl in terms of spatial NICS.

Original languageEnglish
Pages (from-to)4600-4608
Number of pages9
JournalTetrahedron
Volume68
Issue number24
DOIs
Publication statusPublished - Jun 17 2012

Keywords

  • Aminonaphthols
  • Conformational analysis
  • NMR spectroscopy
  • Naphthoxazinoquinazolinones
  • Ring current effect
  • Theoretical calculations

ASJC Scopus subject areas

  • Biochemistry
  • Drug Discovery
  • Organic Chemistry

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