Chemistry of the phenoxathiins and isosterically related heterocycles. XIII. 13C-NMR spectroscopy of 1-azaphenoxathiin 10,10-dioxide. An unusual perturbation of 1H-13C coupling constants

The total assignment of the ¹³C-nmr spectrum of 1-azaphenoxathiin 10,10-dioxide is reported based on the utilization of additivity correlations for the conversion of sulfide to sulfone linkages. Although the benzenoid portion of the molecule obeyed standard additivity correlations, substantial deviation in additivity behavior was observed in the pyridyl portion of the molecule. Examination of the ¹H-¹³C spin-coupling constants showed a perturbation of the primary one bond (¹J_CH) couplings of the C-2 and C-4 carbons.