An unexpected and highly efficient reaction of dibenzo[a,e]cyclooctatetraene with Ag(i)F and N-bromosuccinamide in dichloromethane results in a sequential ring contraction pathway to generate bridged bicyclic α,α'-difluoroether isomers 10 and 11 where the ether oxygen is isotopically labelled from oxygen-18 water. In diethyl ether the same reaction generates the more classical vicinal difluoride isomers 13 and 14.