Gold-catalyzed cycloisomerization of yne-vinylidenecyclopropanes: a three-carbon synthon for [3+2] cycloadditions.

A novel type of yne-vinylidenecyclopropanes (VDCPs) has been synthesized and applied in gold-catalyzed cycloisomerization reactions. It was found that these compounds can undergo an intramolecular cycloisomerization and perform as a three-carbon synthon for [3+2] cycloaddition under gold catalysis to give fused [4.3.0] and [5.3.0] bicyclic derivatives and VDCP rearranged products in moderated to good yields under mild conditions. The substrate scope of these novel transformations has been explored and plausible reaction mechanisms have been presented on the basis of deuterium labeling experiments and DFT calculations.