Facile oxidative cyclization to access C2-quaternary 2-hydroxy-indolin-3-ones: synthetic studies towards matemone

Abstract

A concise and facile approach for the construction of 2-hydroxy-2-substituted indol-3-ones was developed through an oxidative cyclization of 2-aminophenyl-1,3-dione. Using CAN and TEMPO as oxidants, C2-quaternary 2-hydroxy-indolin-3-ones were efficiently installed in moderate to excellent yields (up to 99%). Moreover, this developed protocol was further applied to synthetic studies towards natural product matemone by starting from readily available 2-amino-4-bromobenzoic acid, and the precursor for matemone was efficiently installed.