Gold (I) catalyzed intermolecular cycloadditions of allenes

Résumé

We describe our efforts in the development of intermolecular Au-catalyzed cycloadditions with allenic scaffolds. In particular, we demonstrate that the use of allenamides, a particularly accessible and versatile type of allenic scaffold, allowed the discovery of highly selective and even enantioselective gold-catalyzed (4 + 2) cycloadditions to 1,3-dienes. We also pursue the development of a gold-catalyzed intermolecular (2 + 2) cycloaddition, which could be eventually achieved using appropriate alkenes and a phosphite-gold catalyst. Finally, a simple and highly versatile cascade cycloaddition between allenamides and carbonyl-tethered alkenes, including several enantioselective examples, is also described. This method enables a straightforward and highly efficient entry to oxa-bridged seven-, eight- and even nine-membered rings.