Cyclisation of arylnitrenium ions to the aporphine ring system: remarkable formation of a sixteen-membered ring by an intramolecular electrophilic aromatic substitution

Abstract

The delocalised π-cations from 1-(m-nitreniobenzyl)-1,2,3,4-tetrahydroisoquinolines cyclise to 9-and 11-aminoaporphines, but the p-nitrenium isomers do not form a 5-membered ring unless the ring undergoing attack is strongly activated; on the other hand, 1-(p-nitreniobenzyl)-7-benzyloxy-6-methoxy-2-methyl- 1,2,3,4-tetrahydroisoquinoline undergoes a remarkable intramolecular electrophilic substitution to give (8)(confirmed by an X-ray study) containing a 16-membered ring.