Merging synthesis and enantioselective functionalization of indoles by a gold-catalyzed asymmetric cascade reaction.

Significance: The authors developed a gold-catalyzed hydroamination followed by an asymmetric nucleophilic allylic substitution cascade to access oxazino[4,3-a]indoles in good yields and enantioselectivities. Owing to pharmacologically active indole alkaloids, this rapid synthesis and asymmetric decoration of the polycyclic indolyl core is highly important. Comment: Amazingly, the stereodifferentiating event in this gold-catalyzed asymmetric domino process takes place at the late stage, which is somewhat unusual and more challenging. Extensive mechanistic studies support the stepwise SN2′-type mechanism for the final allylic alkylation ring closure (cycle II). [L(AuCl)2]/AgNTf2 (5 mol%) PhMe, 0–25 °C, 2–24 h