Stereoselective Synthesis of Spiro‐Azacycles Through Tri‐bromide Mediated Oxidative Dearomatization

A metal‐free one‐pot approach towards a highly stereoselective synthesis of N‐substituted spiro‐azacyclodienones, dihydro spiro‐azacyclodienones and spiro‐lactams have been reported in this present work. Phenyl tri‐methyl ammonium tri‐bromide (PTAB) as an effective reagent has been employed for intramolecular spiro‐cyclizations via the key oxidative dearomatization reaction. Interestingly, the obtained N‐substituted spiro‐azacyclodienones was readily transformed into strained cyclopropanated spirocycles. A straightforward synthesis of N‐substituted spiro‐azacycles from υ‐amino naphthol is presented trough PTAB mediated oxidative dearomatization. In the process, the N‐substituted spiro‐azacyclodienones were readily transformed into strained cyclopropanated spiro‐cycles.