Imidoylketene−Oxoketenimine Interconversion. Rearrangement of a Carbomethoxyketenimine to a Methoxyimidoylketene and 2-Methoxy-4-quinolone

FVP of triazole 13 produces the isolable ketenimine 11 together with indole 15. 11 undergoes reversible interconversion with imidoylketene 10 above 380 °C. The latter cyclizes to quinolone 12. Meldrum's acid derivative 16 produces the same ketene 10 above 200 °C, and the latter isomerizes to ketenimine 11 at 200 °C by a 1,3-shift of a MeO group. A competing elimination of MeOH from 16 produces (phenylimino)propadienone 20.