The Cope rearrangement is an extensively studied organic reaction involving the [3,3]-sigmatropic rearrangement of 1,5-dienes. It was developed by Arthur C. Cope. For example 3-methyl-1,5-hexadiene heated to 300°C yields 1,5-heptadiene.
The Cope rearrangement causes the fluxional states of the molecules in the bullvalene family.