Enantioselective Synthesis of Spiroketals and Spiroaminals via Gold and Iridium Sequential Catalysis

The enantioselective cascade reaction between racemic 2‐(1‐hydroxyallyl)phenols and alkynols/alkynamides was realized by using a gold and iridium sequential catalytic system. In this procedure, the in situ generated exocyclic vinyl ethers or enamides undergo the asymmetric allylation/spiroketalization with π‐ally‐Ir amphiphilic species, which provides an efficient and straightforward access to spiroketals and spiroaminals with excellent enantioselectivities. Moreover, racemic 2‐(1‐hydroxyallyl)anilines were also suitable in this reaction along with a kinetic resolution process, affording enantioenriched spiroaminals and 2‐(1‐hydroxyallyl)anilines in good yields. The synthetic utility of this method has been demonstrated by efficient enantioselective synthesis of the analogue of Paecilospirone. An asymmetric cascade reaction of 2‐(1‐hydroxyallyl)phenols/2‐(1‐hydroxyallyl)anilines with alkynyl alcohols/amides was realized by using a novel Au/Ir sequential catalytic system, which enables the facile synthesis of structurally diverse spiroketals and spiroaminals with up to high diastereoselectivities and excellent enantioselectivities.