Mn(iii)-mediated oxidative cyclisation via C(sp3)–H functionalisation: an efficient strategy for benzo-fused aza-heterocycle synthesis

Abstract

We present an effective Mn(III)-mediated approach for the C(sp³)–H functionalisation of N-aryl cyclic amines and their intramolecular coupling with a malonate partner. This methodology facilitates the efficient synthesis of six- to nine-membered benzo-fused tetrahydroquinoline and benzo[b]azepine dicarboxylates under mild conditions. The methodology avoids the use of harsh oxidants, with Mn(III) playing a key role in the oxidative annulation of N-aryl cyclic amines with malonates. It demonstrates high functional-group tolerance and operational simplicity. Overall, this approach provides a sustainable and practical alternative to traditional hydride-shift-based methods for accessing diverse benzo-fused aza-heterocycles.