On treatment with Bu^tLi and HMPA, N-tert-butyl-N-benzyl-1-naphthamide undergoes cyclisation to a tricyclic enolate which reacts diastereoselectively with electrophiles to give substituted 2,3,3a,9b-tetrahydro-1H-benzo[e]isoindol-1-ones, the first example of an anionic cyclisation onto an aromatic ring.