Synthesis of Spiro[benzo[<i>d</i>][1,3]oxazine-4,4′-isoquinoline]s via [4+1+1] Annulation of <i>N</i>-Aryl Amidines with Diazo Homophthalimides and O₂

Abstract

Synthesis of spiro[benzo[<i>d</i>][1,3]oxazine-4,4'-isoquinoline]s through a unique [4+1+1] annulation of <i>N</i>-aryl amidines with diazo homophthalimides and O₂ is presented. This unprecedented spirocyclization reaction features readily obtainable substrates, structurally and pharmaceutically attractive products, a cost-free and clean oxygen source, sustainable reaction medium, tolerance of a broad spectrum of functional groups, and an interesting reaction mechanism based on sequential C(sp²)-H/C(sp³)-H bond cleavage and oxygen insertion.