Gold-Catalyzed Reactions of Cyclopropenes

Cyclopropenes have often been used as substrates in transition metal-promoted or catalyzed reactions. Since the first reports in 2008, gold-catalyzed reactions of cyclopropenes have rapidly evolved to an active research field. The observed reactivity is essentially related to the ability of cyclopropenes to undergo ring-opening in the presence of gold(I) complexes and hence generate alkenyl gold carbenoids. These latter organogold species act as key reactive catalytic entities in a wide range of transformations including inter- or intramolecular nucleophilic additions of heteroatom or carbon nucleophiles, carbene-type coupling reactions and olefin cyclopropanations. Additionally, cyclopropenes can also behave as π nucleophiles in gold-catalyzed enyne cycloisomerizations wherein alkynes are preferentially activated by gold(I) complexes. A wide variety of acyclic and cyclic products can be produced by these gold-catalyzed reactions of cyclopropenes and the different contributions as well as the theoretical studies in this field have been summarized in this chapter. Keywords: carbenoids; catalysis; cyclopropanation; cyclopropenes; gold complexes; nucleophilic additions; rearrangement; ring-opening