Gold(I)-catalyzed divergence in the reactivity of 3-silyloxy 1,6-enynes: Pinacol-terminated vs claisen-terminated cyclization cascades

On activation with catalytic amounts of gold(I) complexes, 3-silyloxy 1,6-enynes can react through two alternative pathways. In one, a cascade reaction consisting of carbocyclization and subsequent pinacol rearrangement takes place. In the second pathway, a heterocyclization is followed by a Claisen rearrangement. The reaction outcome differs depending on the substitution pattern of the 3-silyloxy 1,6-enynes and, more importantly, the electronic properties of the gold-bound phosphane ligand.