tert-Amino Effect in peri-Substituted Naphthalenes: Syntheses of Naphthazepine and Naphthazonine Ring Systems

Novel straightforward syntheses of naphtho-fused azepines and benzazonine via tert-amino effect are described. Starting from 1-naphthylamine, 8-N,N-dialkylaminonaphthalene-1-carbaldehydes could be obtained in two steps. The aldehyde was prepared by a Suzuki reaction of 8-bromonaphthalene-1-carbaldehyde with ortho-pyrrolidinophenylboronic acid. Treatment of aldehydes with active methylene compounds afforded naphthazepines and novel benzazonine ring system, respectively, through rearrangement of isolable vinyl intermediates or benzo[de] quinolinium derivatives or without isolation of any intermediates. A mechanistic investigation supports an intramolecular hydride transfer for the ring closure to azepine or azonine. Our results indicate that the tert-amino effect may provide a valuable approach to the synthesis of ortho-and peri-fused aza-ring systems.