N-Fluorobenzenesulfonimide-Mediated Oxidative Rearrangement of Tetrahydro-β-carbolines

Abstract Oxidative rearrangement of tetrahydro-β-carbolines is recognized as a biosynthetic process and represents one of the most popular and efficient approaches for the synthesis of spiro[pyrrolidine-3,3]oxindoles, which belong to an important structural scaffold that widely exists in a wide spectrum of pharmaceutically active compounds and natural products. Although halogenated reagents including t-BuOCl, NBS, and NIS, have been frequently used as oxidants for this oxidative rearrangement, fluorinated reagents have not been successfully employed. Here, a universal and efficient oxidative rearrangement of tetrahydro-β-carbolines using N-fluorobenzenesulfonimide (NFSI) as the oxidant is reported, affording a variety of spiro[pyrrolidine-3,3]oxindoles in excellent yields (90–99%). Owing to the increased oxidative ability and hardness of fluorine over other halogens, this method would be instrumental to rapid access of structurally diverse spirooxindoles.