A Dearomatization/Debromination Strategy for the [4+1] Spiroannulation of Bromophenols with α,β‐Unsaturated Imines

A novel [4+1] spiroannulation of o ‐ & p ‐bromophenols with α,β‐unsaturated imines has been developed for the direct synthesis of a new family of azaspirocyclic molecules. Notably, several other halophenols (X=Cl, I) were also applicable for this transformation. Moreover, a catalytic asymmetric version of the reaction was realized with 1‐bromo‐2‐naphthols by using a chiral Sc III /Py‐Box catalyst. Mechanistic studies revealed that this domino reaction proceeded through electrophile‐triggered dearomatization of phenol derivatives at their halogenated positions and followed by halogen‐displacement with N ‐nucleophiles via a radical‐based S RN 1 mechanism.