2-Polyfluoroalkylchromones 12. Nitration of 5,7-dimethyl-2-polyhaloalkylchromones and complete assignment of signals in the ¹H and ¹³C NMR spectra of 5,7-dimethyl-2-trifluoromethylchromone and its mono- and dinitro derivatives

Abstract:

The nitration of 5,7-dimethyl-2-polyhaloalkylchromones affords either 5,7-dimethyl-6-nitro- or 5,7-dimethyl-6,8-dinitro-2-polyhaloalkylchromones, depending on the reaction conditions. Signals in the 1H and 13C NMR spectra of the sterically hindered chromones were completely assigned using the 2D NOESY, HETCOR, and COLOC spectra. The influence of nonplanar nitro groups on chemical shifts of carbon atoms was studied. Some spectral peculiarities of the peri-methyl group were revealed. The 1H-1H and 13C-1H spin-spin coupling constants, including the extreme six-bond long-range coupling between the protons of the Me(5) group and H(8), were determined.

Año de publicación:

2002

Keywords:

• Spin-spin coupling constants
• Sterically hindered nitro groups
• Nitration
• 2-polyhaloalkylchroman-4-ones
• 1 13 H and C NMR spectroscopy
• 2-polyhaloalkylchromones
• peri-methyl group
• Increments of substituent chemical shifts

Fuente:

scopus