The functionalisation of two neighboring beta-pyrrolic positions of a porphyrin by a fused N-heterocyclic carbene ligand, the subsequent metallation of this external coordination site by palladium(II) and the structural characterisation of the resulting compounds are presented.

The Diels-Alder reaction between 2,5-dimethylfuran and vinylene carbonate was studied, both from an experimental and a theoretical point of view. The system was shown to slowly reach a thermodynamic equilibrium, characterized by the almost exclusive formation of the exo isomer. We rationalized these results by a comparison with classical systems involving maleic anhydride, and highlighted the different reactivity of vinylene carbonate as a dienophile. Finally, a preparative scale synthesis of pure exo isomer 4, a potentially useful synthon, ensued from this work.