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. (C) 2011 Elsevier B.V. All rights reserved.