Structural characterization of isomeric 2,3,5-substituted tetrahydropyrrolo[3,4-d]isoxazole-4,6-diones prepared by cycloaddition of N-methyl-C-arylnitrones to N-phenyl- or N-methylmaleimide

Pihlaja K., Tahtinen P., Shaikhutdinov R., Hartikamen H., Ovcharenko V., Agirbas H., ...More

JOURNAL OF HETEROCYCLIC CHEMISTRY, vol.41, no.5, pp.741-746, 2004 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 41 Issue: 5
  • Publication Date: 2004
  • Doi Number: 10.1002/jhet.5570410515
  • Journal Name: JOURNAL OF HETEROCYCLIC CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.741-746
  • Kocaeli University Affiliated: Yes

Abstract

1,3-Dipolar cycloaddition reactions of N-methyl-C-arylnitrones with N-phenyl- or N-methylmaleimide were studied. The reaction of p-dimethylamino-, 4-benzyloxy-3-methoxy-, p-nitro- and p-chloro- substituted phenylnitrones with N-phenylmaleimide gave cis and trans cycloadducts but that of the corresponding phenylnitrones with N-methylmaleimides only the cis adducts in the case of p-dimethylamino and 4-benzyloxy-3-methoxy substitution. All cis adducts attain a biased conformation whereas the trans forms are shown (by H-1 NMR at 233 K and C-13 NMR at 208 K) to be mixtures of two invertomers, namely o- (N-lone pair antiperiplanar to 3H; minor) and i-conformations (3H-C-C-3aH dihedral angle close to 90degrees; major). PM3 and DFT calculations at the B3LYP/6-31G(d) level of theory prove qualitatively that these two conformers of the trans adduct are of comparable stability and represent energy minima.