One-pot preparation of derivatives of the unknown fluoreno[2,3,4-i,j]isoquinoline ring from conjugated ketenimines by a consecutive electrocyclic ring-closure/Claisen rearrangement/intramolecular Diels–Alder cycloaddition/double aromatization process

Abstract

A short synthesis of fluoreno[2,3,4-i,j]isoquinoline derivatives (8) based on a new method of three consecutive annelations which involves thermal cyclization of conjugated ketenimines is described; the crystal structure of (8) has been determined.