A Dearomatization/Debromination Strategy for the [4+1] Spiroannulation of Bromophenols with α, β‐Unsaturated Imines. (24th August 2020)

• Record Type: Journal Article
• Authors: Ge, Yicong; Qin, Cheng; Bai, Lu; Hao, Jiamao; Liu, Jingjing; Luan, Xinjun
• Is Part Of: Angewandte Chemie. Volume 132:Number 43(2020)
• Page Start: 19147
• Page End: 19151
• Publication Date: 2020-08-24
• Subjects: bromophenol -- dearomatization -- debromination -- spiroannulation -- synthetic methods; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202008130
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: 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 SRN 1 mechanism. Abstract : An unprecedented [4+1] spiroannulation of halophenols with α, β‐unsaturated imines has been developed for the rapid assembly of highly valuable azaspirocycles. This intermolecular domino reaction was realized through a sequence of electrophile‐triggered dearomatization of phenol derivatives at their halogenated sites and followed by halogen‐displacement with N ‐nucleophiles via a radical‐based SRN 1 mechanism.