Crystal structures, packing features, Hirshfeld surface analyses and DFT calculations of hydrogen-bond energy of two homologous 8a-aryl-2,3,4,7,8,8a-hexahydropyrrolo[1,2-a]pyrimidin-6(1H)-ones

Abstract

The crystal structures and packing features of two homologous Meyer's bicyclic lactams with fused pyrrolidone and medium-sized perhydropyrimidine rings, namely, 8a-phenyl-2,3,4,7,8,8a-hexahydropyrrolo[1,2-a]pyrimidin-6(1H)-one, C₁₃H₁₆N₂O (1), and 8a-(4-methylphenyl)-2,3,4,7,8,8a-hexahydropyrrolo[1,2-a]pyrimidin-6(1H)-one, C₁₄H₁₈N₂O (2), were elucidated, and Hirshfeld surface plots were calculated and drawn for visualization and a deeper analysis of the intermolecular noncovalent interactions. Molecules of 1 and 2 are weakly linked by intermolecular C=O...H-N hydrogen bonds into chains, which are in turn weakly linked by other C=O...H-C_ar interactions. The steric volume of the substituent significantly affects the crystal packing pattern.

Keywords: DFT calculations; Hexahydropyrrolo[1,2-a]pyrimidin-6(1H)-one; Hirshfeld surface analysis; Meyer's bicyclic lactam; crystal structure; hydrogen bonds; noncovalent interactions.