Transition-metal-free intramolecular carbene aromatic substitution/Büchner reaction: synthesis of fluorenes and [6,5,7]benzo-fused rings.

Intramolecular aromatic substitution and Büchner reaction have been established as powerful methods for the construction of polycyclic compounds. These reactions are traditionally catalyzed by Rh(II) catalysts with α-diazocarbonyl compounds as the substrates. Herein a transition-metal-free intramolecular aromatic substitution/Büchner reaction is presented. These reactions use readily available N-tosylhydrazones as the diazo compound precursors and show wide substrate scope.