Synthesis, structure and some reactions of a multi-bridged unsaturated cyclooctadecane derivative formally having two cycloheptatrienes

Double annulation of 1,6-bis(bromomethyl)-1,3,5-cycloheptatriene with diethyl acetonedicarboxylate under basic conditions provided the title cyclooctadecane derivative having formally two 1,3,5-cycloheptatriene moieties. An NMR study of the compound suggested that one moiety stays as a cycloheptatriene form and the other as a norcaradiene form. X-ray crystallographic analysis revealed that two methano bridges have syn- and anti-configurations to the central carbonyl bridge and also showed that one of the moieties having the syn-methano bridge stays a CHT form and the other having the anti-methano bridge stays an NCD form.