title: A facile synthesis of pyrrolo-(di)-benzazocinones via an intramolecular N-acyliminium ion cyclisation.
abstract: A facile, moderate to high yielding synthesis of hexahydro-(di)-benzazocinones is described via an intramolecular N-acyliminium ion cyclisation. The iminium ion intermediates are formed from the readily available 4,4-diethoxybutyl amides with an excess of triflic acid. For electron-withdrawing substituents, better yields were obtained from the pre-formed 2-hydroxypyrrolidine amides. From NMR studies, at ambient temperatures the pyrrolo-benzazocin-3-ones exist as a slowly equilibrating mixture of two conformations.
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK. f.d.king@ucl.ac.uk
authors.forename: Frank D
authors.initials: FD
authors.lastname: King
authors.forename: Abil E
authors.initials: AE
authors.lastname: Aliev
authors.forename: Stephen
authors.initials: S
authors.lastname: Caddick
authors.forename: Derek A
authors.initials: DA
authors.lastname: Tocher
authors.forename: Denis
authors.initials: D
authors.lastname: Courtier-Murias