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.

The cyclohetratriene–norcaradiene equilibrium of the right wing part in the title compound was found to be shifted to the norcaradiene side.Figure optionsDownload as PowerPoint slide