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

A novel [4+1] spiroannulation ofo- &p-bromophenols with alpha,beta-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 withN-nucleophiles via a radical-based S(RN)1 mechanism.