Synthesis of benz[5,6]azepino[4,3-b]indoles by 1,7-electrocyclisation of azomethine ylides

A new, general route to the benz[5,6]azepino[4,3-b]indole ring system has been developed via the 1,7-dipolar electrocyclisation reactions of azomethine ylides derived from easily available 3-formyl indole derivatives. The intermediacy of azomethine ylides was shown by the trapping of the proposed α,β:γ,δ-conjugated dipole with N-phenylmaleimide.