Synthesis of Dibenzo[<i>g,p</i>]chrysenes from Bis(biaryl)acetylenes via Sequential ICl-Induced Cyclization and Mizoroki−Heck Coupling

We report a facile synthesis of functionalized dibenzo[<i>g</i>,<i>p</i>]chrysenes via initial ICl-promoted cyclization of bis(biaryl)acetylenes, followed by the Mizoroki−Heck coupling reaction. This new approach works well for various bis(biaryl)acetylenes to afford dibenzo[<i>g</i>,<i>p</i>]chrysenes bearing various functionalities. With substrates of one special type including 4‘-methoxy-2-ethynylbiphenyls, we found that the ICl treatment led to <i>ipso</i> cyclization to give bicyclic spirocyclohexadienones. In the presence of MeOH/H₂SO₄, these spiroketone products undergo rearrangement to give 9-iodophenanthrenes through a selective 1,2-alkenyl migration. We prepared various 4‘-methoxy-2-ethynylbiphenyl compounds to show the generalization of such an <i>ipso</i> cyclization and 1,2-alkenyl shift. This <i>ipso</i>-cyclization approach can be extended to the preparation of dibenzo[<i>g</i>,<i>p</i>]chrysenes.