A facile synthesis of pyrrolo-(di)-benzazocinones via an intramolecular N-acyliminium ion cyclisation.
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.
King
Frank D
FD
Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK. f.d.king@ucl.ac.uk
Aliev
Abil E
AE
Caddick
Stephen
S
Tocher
Derek A
DA
Courtier-Murias
Denis
D