Gold-Catalyzed β‑Regioselective Formal [3 + 2] Cycloaddition of Ynamides with Pyrido[1,2‑<i>b</i>]indazoles: Reaction Development and Mechanistic Insights

Here, we report an unprecedented gold­(I)-induced β-site regioselective formal [3 + 2] cycloaddition of ynamides with pyrido­[1,2-b]­indazoles, giving 3-amido-7-(pyrid-2′-yl)­indoles in good to excellent yields. A complex of gold­(I) catalyst with ynamide was isolated and characterized by X-ray diffraction analysis for the first time. Mechanistic investigations suggest the reaction pathway involves a gold-stabilized carbocation intermediate, which in turn participated in sequential C–H bond functionalization of the ortho-position of the phenyl ring.