An Investigation on the Synthesis of New Molecular Architectures from the Cyclotrimerisation of exo- and endo-Benzotricyclo[4.2.1.02,5]nonene

We have performed an investigation on the cyclotrimerisation of molecules having exo- and endo-benzotricyclo[ 4.2.1.02,5]nonene skeletons (3 and 4) with the aim of producing their respective cyclotrimers 2 that feature unusual geometries and electronic properties. Activation towards the cyclotrimerisation reaction was performed using the vic-bromostannyl vinyl derivatives and was accomplished under copper-mediated or palladium-catalysed reaction conditions. While the exo isomer 3 proved to be quite reactive and afforded variable amounts of the syn and anti cyclotrimers, the endo isomer 4 turned out to be quite resistant to cyclotrimerisation because of steric hindrance. Only dimers and acyclic trimers were obtained from reactions using this substrate.