X-ray crystallography and computational studies of a variety of pyrrole derivatives obtained from mesoionic oxazoles and selected chromenones

The molecular structure, packing properties, and intermolecular interactions of a series of pyrrole derivatives have been determined by single-crystal X-ray diffraction. They were efficiently synthesized from mesoionic oxazoles and selected chromenones via initial 1,3-dipolar cycloaddition followed by cascade transformations. Compounds 4-6 are described as three fused rings associated in the crystal lattice through H-bonding interactions. Besides the H-bonding interactions encountered in the crystal packing of 4-8, a different strong centrosymmetric pi-interaction has been found in 8, involving the cyano group and the pi-system of aromatic pyrrole ring. A density functional theory (DFT) study was carried out on the supramolecular dimer in order to understand the nature and role of this intermolecular force in driving the molecular packing.