Acid-catalysed intramolecular Friedel-Crafts annulation of hetero-atom-functionalized para -quinone methides: access to O-, S- and N-based heterocycles.

We describe here an acid-mediated one-pot approach to access substituted xanthene and thioxanthane derivatives from ortho -heteroaryl phenyl-substituted para -quinone methides via 1,6 intramolecular arylation. The scope of this work was further elaborated to the synthesis of 10 H -indolo[1,2- a ]indole-based heterocyclic systems using indole based para -quinone methides.