An efficient synthesis is described of hexabromides 5 and 6 by photobromination of biphenylene (1). Double dehydrobromination of hexabromides 5 and 6 with t-BuOK affords 5, 6, 8, 10-tetrabromobenzocyclooctene (7) in nearly quantitative yield. The tetrabromide 7 is a valuable precursor for the preparation of functionalised substituted benzocyclooctenes (benzo [8] annulenes).
