High Yield Synthesis of Spirocyclic Dienones from Phenols Employing Tribromide Catalysed Dearomatization.

A catalytic strategy towards the tribromide‐catalyzed dearomative spirocyclization reaction is described employing tetrabutylammonium bromide (TBAB) and oxone as an oxidising agent. This methodology leads to the exclusive formation of spirofurano dienones without rearomatization or halogenation. Our group has been on trails of tribromide‐catalyzed dearomative transformation during the last decade, and now this exhibits the first report which delivers high functional group tolerance and broad substrate scope with excellent yield (up to 99 %) and good diastereoselectivity (dr up to 14 : 1). The oxidation of naphthols as well as phenols is achieved under this mild conditions. [ABSTRACT FROM AUTHOR]