Tandem [4 + 2]/[2 + 2] Cycloaddition Reactions Involving Indene or Benzofurans and Arynes

The
reaction of arynes with indene/benzofurans has been developed.
The arynes were generated from 2-(trimethylsilyl)­aryl triflates by
the fluoride-induced 1,2-elimination react with indene or various
benzofurans proceeding via a cascade reaction involving the Diels–Alder
reaction and a [2 + 2] cycloaddition reaction. The tandem process
afforded functionalized dihydrobenzocyclobutaphenanthrenes in moderate
to good yields. Moreover, the method has been utilized for the one-pot
synthesis of benzo­[b]­fluoranthene.