Conformational study of N,N-dimethyl-1,3-diaza-5,6-benzocycloheptene

¹H and ¹³C variable temperature NMR results show that the seven-membered heterocycle $\text{2}$ exists solely in the Cea form, a situation very different from the analogous six-membered $\text{1}$ which exists predominantly in the Cee form.