From Ketenimines to Ketenes to Quinolones: Two Consecutive Pseudopericyclic Events

N-[2-(Alkyl- or arylthio)carbonyl]phenyl ketenimines undergo cyclization under mild thermal conditions to afford 2-alkyl(aryl)thio-3H-quinolin-4-ones by means of the 1,5-migration of the alkyl(aryl)thio group from the carbonyl carbon to the central carbon atom of the ketenimine
fragment followed by the 6π-electrocyclization of the resulting vinyliminoketene. These 1,5-migration and electrocyclization processes occur
via transition states whose pseudopericyclic characteristics have been established on the basis of their magnetic properties, geometries, and
NBO analyses.