Synthesis of Highly Functionalized Indolizines via NIS-Promoted Spiroannulation/Ring-Opening Aromatization of Alkylidene Oxindoles with 2-(Pyridin-2-yl)acetate Derivatives

A novel NIS-promoted domino reaction of alkylidene oxindoles with 2-(pyridin-2-yl)acetate derivatives has been established, enabling the efficient and straightforward synthesis of a vast variety of highly functionalized indolizines via sequential spiroannulation and ring-opening aromatization processes. The protocol features mild reaction conditions, broad substrate scope, high efficiency, scalability, and applicability for the preparation of CF3-containing indolizines. Furthermore, the functional groups in the indolizine framework provide the feasibility for follow-up derivatization. Based on mechanistic studies, a plausible radical mechanism is proposed to elucidate the formation of indolizines.