Thia-acyliminium cyclisations

Cyclisations of carbinollactams 1b-3b afford macrocycles 4-6 in good yield by the intermediacy of N-acyliminium species. A similar process applied to lactams 21b-25b affords the pyrrolizidine type compounds 26-35 through consecutive azonium-Cope rearrangement and N-acyliminium ring closure. Additional results are concerned with the use of aromatic rings as π-nucleophiles.