Abstract
Isoquinoline N-oxide (5) and N-imine (8) were prepared by ring-opening reactions of quarternary isoquinolinium salts and successive ring-closures. The ring-opening reaction of N-(2, 4-dinitrophenyl) isoquinolinium chloride (1) with hydroxylamine gave o-[2-(2, 4-dinitroanilino) vinyl] benzaldehyde oxime (2), which cyclized by refluxing in concentrated hydrochloric acid-ethanol (3 : 40) to isoquinoline N-oxide (5) in 53% yield from isoquinoline. This method was applied to the preparation of isoquinoline N-imine (8). An equimolar mixture of N-(2, 4-dinitrophenyl) isoquinolinium chloride (1) and hydrazine hydrate in dioxane-water (4 : 1) was heated under reflux to give isoquinoline N-imine (8) in 50% yield from isoquinoline.
