Two-pot synthesis of unsymmetrical hetero[7]helicenes with intriguing optical properties

A two-pot synthesis of unsymmetrical hetero[7]helicenes from commercially available substrates has been established. Combining the acid-mediated annulation with the electrochemical domino reaction (oxidative hetero-coupling/dehydrative cyclization sequence) in a single protocol afforded oxaza[7]helicenes with up to 45% overall yield. The photophysical properties of these [7]helicenes have been studied, and their absorption and fluorescence patterns were explained by DFT calculations.