Base-Promoted Domino Reaction of o -Amino/Hydroxy Chalcones with In Situ Formed Isocyanates from Dioxazolones: Divergent Synthesis of Quinazolinones and Benzoxazinones

Herein, we disclose a tertiary amine-promoted domino reaction enabling facile one-pot synthesis of quinazolinones and benzoxazinones in moderate to excellent yields (up to 97%). This transition-metal-free protocol operates under simple reaction conditions, employing readily accessible ortho-amino/hydroxy chalcones to facilitate annulation with in situ generated isocyanates from dioxazolones. The reaction proceeds through a cascade sequence of decarboxylation, Lossen rearrangement and formal [4 + 2] annulation, forming three new C-X bonds in a single operation. Moreover, this domino strategy exhibits broad substrate scope and outstanding functional group tolerance.