Morpholines-(III): Some Further Aspects of the Cyclodehydrohalogenation of ω -[N-(aryl)-N-(halogenoacyl)]-aminoacetophenones

Abstract

The formation of a 2-oxo-azetidine from N-phenyl-N-chloroacetyl-4-fluoro-phenacylamine, and 3-oxo-morpholines from corresponding 4-bromo-derivatives 2 indicates the possibility of the existence of dπ-acceptor resonance between the aromatic ring and the bromo-substituent. H-NMR studies of some morpholines reported earlier 3 indicate a planar heterocyclic structure with a rapidly inverting N₋aryl substituent. Where the rotation of the N-aryl group is strongly hindered 16, the C2 methylene protons show a geminai coupling of -14.5 Hz4. The 2-oxo-azetidine (4) shows an ABX coupling pattern for its ring protons. Preliminary work attempting to extend the synthesis of morpholines to azepines has resulted instead in the formation of a pyrrolidone.