Intermolecular cyclopropanation reactions of enynes with alkenes allows the synthesis of complex cyclic systems with gold(I) catalysts under mild conditions. Furthermore, gold carbenes are trapped intermolecularly with alkenes (see scheme; L=ligand), thereby providing experimental evidence for the involvement of two different types of metal carbenes in the skeletal rearrangement of enynes.
Gold(I)-Catalyzed Intermolecular Cyclopropanation of Enynes with Alkenes: Trapping of Two Different Gold Carbenes
Angew. Chem. Int. Ed. 2006, 45, 6029-6032.