A free radical cyclization approach to indolo-benzodiazocine derivatives

A versatile route to indolo[2,1-d][1,5]benzodiazocine derivatives has been developed based on a free radical cyclization approach from 1-substituted indole derivatives with appropriately positioned haloacetamide functionalities. Fair yields of the indole- and dihydroindole-fused eight-membered ring derivatives were obtained from N-substituted iodo- and bromoacetamide precursors. Synthetic and mechanistic aspects of the regiospecific cyclization are discussed.