Conformational analysis: 30 - A 1H and 13C NMR stereochemical study on N-methyl-substituted cis- and trans-fused octahydro-2H-1,3- and -3,1-benzoxazines

Kalevi Pihlaja, Jorma Mattinen, F. Fülöp

Research output: Contribution to journalArticle

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Abstract

The 1H and 13C NMR spectra of cis- and trans-fused N-methyloctahydro-2H-1,3- and -3,1-benzoxazines and their 2-methyl derivatives were analysed. All trans-fused derivatives studied existed in biased double chair conformations with roughly equal contributions of the equatorial and axial N-methyl groups. Of the cis-fused isomers, both N-methyl-octahydro-2H-1,3-benzoxazine and its 2-methyl derivative attain exclusively the O-in conformation, whereas N-methyloctahydro-2H-3,1-benzoxazine is not conformationally homogeneous but a ca. 3:1 mixture of the N-in and N-out forms at 198 K and a 7:3 mixture at ambient temperature. Similarly, the 2-methyl derivative of N-methyloctahydro-2H-3,1-benzoxazine was found to be a ca. 3:2 mixture of C-2 epimers with the N-in and N-out conformations, respectively.

Original languageEnglish
Pages (from-to)998-1002
Number of pages5
JournalMagnetic Resonance in Chemistry
Volume34
Issue number12
DOIs
Publication statusPublished - Dec 1996

Fingerprint

Benzoxazines
Nuclear magnetic resonance
Derivatives
Conformations
nuclear magnetic resonance
seats
ambient temperature
isomers
Isomers
Temperature

Keywords

  • H NMR
  • C N
  • Conformational analysis
  • M
  • NMR
  • Octahydro-2H-1,3-benzoxazines
  • Octahydro-2H-3,1-benzoxazines
  • R

ASJC Scopus subject areas

  • Chemistry(all)
  • Physical and Theoretical Chemistry
  • Spectroscopy

Cite this

Conformational analysis : 30 - A 1H and 13C NMR stereochemical study on N-methyl-substituted cis- and trans-fused octahydro-2H-1,3- and -3,1-benzoxazines. / Pihlaja, Kalevi; Mattinen, Jorma; Fülöp, F.

In: Magnetic Resonance in Chemistry, Vol. 34, No. 12, 12.1996, p. 998-1002.

Research output: Contribution to journalArticle

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