The thermal [3,3]-sigmatropic rearrangement of 1,5-dienes to the isomeric form is known as the Cope rearrangement, which can only be detected when the 1,5-diene substrate is substituted. As a reversible reaction, the forward direction is favored when the product is stabilized by conjugation or the resulting double bond is more highly substituted. A chair-like transition state renders the reaction both stereospecific and stereoselective, favoring least steric interactions between substituents.