Assignments of ¹H And ¹³C NMR of 6(9)-Methyl-Benzo[b]naphthyridines (5-Methyldiazaanthracenes)

Abstract

A complete assignment of the ¹H and ¹³C NMR spectra of four 6(9)-methylbenzo[b]naphthyridines in CDCl₃ is presented. The proton signals have been assigned from (¹H-¹H) coupling patterns and by the comparisons of chemical shifts with those of related heterocycles. Complete ¹³C assignments have been made using proton detected one bond (¹³C-¹H) 2D heteronuclear single quantum correlation, the INEPT technique, and chemical shift comparisons with related heterocycles. The proton detected long range (¹³C-¹H) 2D heteronuclear multiple quantum correlation experiment leads to an unambiguous assignment of the two quaternary carbons in 6-methyl-benzo [b][1,5] naphthyridine.

Key Words:

• Diazaanthracenes
• Benzo[b]naphthyridines
• ¹H and ¹³C NMR assignments
• 2D Correlation Spectroscopy
• Heteronuclear Multiple Bond Correlation (HMBC)
• Heteronuclear Single Quantum Correlation (HSQC)