Mechanistic switch in dual gold catalysis of diynes: C(sp(3))-H activation through bifurcation--vinylidene versus carbene pathways.

The other side of the mountain: Changing the framework of diyne systems opens up new cyclization modes for dual gold catalysis. Instead of a 5-endo cyclization and gold vinylidenes a 6-endo cyclization gives rise to gold-stabilized carbenes as key intermediates for selective C-H insertions.