The preparation of stereoisomeric tricyclo[4.2.1.02,5]nona-7-ene-3,4-dicar­boximides and anhydrides : literature corrections and new products

The bis-homo Diels-Alder reactions of maleimide and N-methylmaleimide with quadricyclane are shown to produce mixtures containing both the exo, anti- and exo, syn-tricyclo-[4.2.1.02,5] nona-7-ene-3, 4-dicarboximides, whereas the isomeric endo, anti-adducts are available from the reaction of cyclopentadiene with the appropriate cyclobutene-3, 4-dicarboximides. The related reaction of quadricyclane with maleic anhydride had been erroneously reported to form single adducts; our work shows that two stereoisomers are actually formed and these have been chemically related to the maleimide and N-methylmaleimide adducts. The proton chemical shifts of the adduct formed by reaction of cyclobutene-3, 4-dicarboxylic anhydride with cyclopentadiene have also been miss-assigned. Preparation of [3] and [5] polynorbornane scaffolds with terminal succinimides have been effected by coupling the stereoisomeric adducts at the norbornene π-bond by using 2, 5-bis(trifluoromethyl)-1, 3, 4- oxadiazole and bisepoxide. The spacer shapes and dimensions have been determined by molecular modelling.