Transition-Metal-Free Synthesis of N-Hydroxy Oxindoles by an Aza-Nazarov-Type Reaction Involving Azaoxyallyl Cations.

A novel transition-metal-free method to construct N-hydroxy oxindoles by an aza-Nazarov-type reaction involving azaoxyallyl cation intermediates is described. A variety of functional groups were tolerated under the weak basic reaction conditions and at room temperature. A one-pot process was also developed to make the reaction even more practical. This method provides alternative access to oxindoles and their biologically active derivatives.