© 2019, The Author(s), under exclusive licence to the Japan Antibiotics Research Association. Communesins, isolated from the mycelium of a strain of Penicillium sp., are cytotoxic heptacyclic indole alkaloids bearing a bis-aminal structure and two contiguous quaternary carbon centers. Toward a total synthesis of communesin F, we synthesized a pentacyclic ABCDG ring skeleton via carboborylation of 1,3-diene and a Friedel–Crafts-type cyclization, resulting in the formation of an azepine ring through a Bi(OTf) 3 -catalyzed S N 2’ reaction.