Creation of concave-shaped conformation in crystal structures using an iminodicarbonyl linker. An application to solid-state intramolecular [4+4] photocycloaddition reactions of 2-pyridone derivatives

Single-crystal X-ray structures of 6 carboxamides possessing two units of 2-pyridone moieties connected with an iminodicarbonyl linker were examined to show the usefulness of this linker for the creation of concave-shaped conformation in crystal structures. In all cases, the carboxamides showed concave-shaped conformations in which two 2-pyridone moieties faced each other. Their solid-state [4 + 4] photocycloaddition was carried out, and their reactivity was considered based on geometrical parameters (distances, angles, and torsion angles) obtained from the single-crystal X-ray analysis.