De novo synthesis of 6-6-5-fused systems by electrochemical decarboxylation and radical domino additions

The highly complex fused systems are widely present in drug development. The direct electrosynthesis of fused systems by radical domino reactions has higher atomic and stepwise economy, using abundantly available starting materials and avoiding exogenous oxidants and reducing agents. Therefore, it is highly demanded and recognized as a green, powerful and versatile synthetic tool, but it remains challenging due to the instability of the radical species under the electrolysis conditions and the addition of the quaternary ammonium salt. Herein, we developed a de novo electrosynthesis of 6-6-5 fused systems with two novel rings constructed using a user-friendly undivided cell by decarboxylation and three-step radical addition under exogenous oxidant- and quaternary ammonium salt-free conditions. Excellent functional group, water and air compatibility were observed with good yields.