N‑Methyl Transfer Induced Copper-Mediated Oxidative Diamination of Alkynes

A novel intramolecular oxidative diamination of bis­(2-aminophenyl)­acetylene for the synthesis of the structurally intriguing π-conjugated polyheterocyclic scaffold, 5,10-dihydro­indolo­[3,2-b]­indole (DHII), has been developed under Cu­(hfacac)2/O2 oxidation systems. The structure design of bis­(2-amino­phenyl)­acetylene bearing both N,N-dimethylamine and primary amine groups is crucial for constructing the corresponding DHII scaffold. Notably, an intermolecular N-methyl transfer from the nitrogen atom of N,N-dimethylamine to the primary amine takes place, which is a critical step for the successful implementation of the present annulation process.