This work is concerned with the involvement of the two possible intramolecular Diels-Alder adducts which can be formed from a 2-allyl-3, 5-cyclohexadienone produced by the Claisen rearrangement of a phenylallyl ether. One of these adducts has been invoked to account for the ortho-ortho ' transformation. Pentafluorophenyl allyl ether was chosen as the starting material, as it was envisaged that the fluorine atoms would a) block enolisation in the dienone intermediates; b) make the proposed Diels-Alder reaction more favourable by furnishing an electron deficient diene; and c) would help to stabilise small ring systems in the product. The thesis is divided into five parts. Chapter one reviews the literature and traces the mechanistic development of the Claisen re arrangement and the ortho-ortho' transformation. In Chapters two and three the isolation and characterisation of aromatic, bicyclic and tricyclic decomposition products, from the two possible intramolecular Diels-Alder adducts, are discussed. Chapters four and five describe the Claisen rearrangement in penta-fluorophenyl 2-methylprop-2-enyl and pentafluorophenyl 2-methylbut-3-en-2-yl ethers and suggest that the products formed can be accounted for by a mechanistic scheme which could be general.