Electro-reductive cyclization of aryl halides promoted by fluorene derivatives

In the presence of fluorene derivatives, the electro-reduction of aryl chlorides, bromides, and iodides bearing an ethylene moiety proceeded smoothly to afford the corresponding cyclized products. Noteworthy is that aryl chlorides, which have more negative reduction potential than aryl bromides and iodides, exhibited high reactivity in the reaction, and the corresponding five-membered and six-membered cyclized products were obtained in good to high yields. Mechanistic study suggests that the electro-reduction of fluorene derivatives was essential for the reactions, indicating that they work as a mediator.