Different Selectivities in the Insertions into C(sp )-H Bonds: Benzofulvenes by Dual Gold Catalysis Competition Experiments.

An unprecedented, often almost quantitative access to tricyclic aromatic compounds by dual gold catalysis was developed. This synthetic route expands the scope of benzofulvene derivatives through a C(sp )-H bond insertion in easily available starting materials. The insertion takes place with an exclusive chemoselectivity with respect to the competing aromatic C-H positions. A bidirectional synthesis with two competing ortho-aryl C-H bonds in the selectivity-determining step also shows perfect selectivity; this result is explained by a computational investigation of the two conceivable intermediates. The intramolecular competition of two non-equivalent aryl C-H bonds with a benzylic methyl group also showed perfect selectivity.