Carbon-13 n.m.r. investigation on the nitrogen methylation of the mono- and diazanaphthalenes

The ¹³C n.m.r. spectra of the N-methylated mono- and diazanaphthalenes have been recorded and analysed. It has been shown that N-methylation as well as N-protonation in cinnoline occur predominantly at the β-nitrogen atom. N-methylation and N-protonation show a similar effect on the ¹³C chemical shifts.