Thermal Behavior of Head-to-head Coumarin Dimers and Their Lactone-opened Derivatives

Abstract

Abstract The thermal behavior of head-to-head coumarin dimers and twelve lactone-opened derivatives was investigated. Though the lactone rings in coumarin dimers are very susceptible to nucleophilic ring-opening, heating these derivatives reformed six-membered lactone rings except for certain imide and diamide derivatives. The large neiboring group effect allowed the relactonization by the attack of hydroxyphenyl group to carbonyl carbon in preference to the scission of cyclobutane ring.