Reactivity studies on 4‐aminopyrones: Access to benzimidazole and benzimidazolone derivatives

Reaction of pyrone 1a or tetronic acid 1b with o‐phenylenediamine derivatives gave enaminone compounds 2 . When reacting with different electrophiles, these intermediates allowed versatile access to different heterocyclic structures: when DMA derivatives or triphosgene was used, cyclization occurred through nitrogen, leading to benzimidazoles 3 and benzimidazolones 4 , respectively, while reaction with benzaldehyde yielded benzodiazepines 5 .