Synthesis of Aza-Eight-Membered Ring-Fused Indolines Initiated by Zn-Catalyzed C2 Alkylation of Indoles and Subsequent Base-Promoted Ring Expansion

A novel and efficient synthesis of aza-eight-membered ring-fused indolines has been developed. This process is realized by zinc-catalyzed C2 alkylation of indoles and subsequent base-promoted ring expansion of the newly formed six-membered ring with alkynes. Easily accessible starting materials, good functional group tolerance, and high atom economy make this procedure attractive.