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.
Key word
tetrahydro-β-carbolines - spirooxindoles - oxidative rearrangement - N–F reagent -
synthetic method
