Investigating structural aspects of Pyridopyrimidinone derivatives, an important precursor in medicinal chemistry

Pyridopyrimidinones are class of heterocyclic compounds which serves as important precursors in organic transformation and medicinal chemistry. In the current work three derivatives of pyrido[1,2-a]pyrimidine-3-carboxylates (1, 2 and 3) has been synthesized and characterized by NMR. The crystal structure of compound 1 (C<inf>12</inf>H<inf>12</inf>N<inf>2</inf>O<inf>3.</inf>HCl) and 2 (2(C<inf>12</inf>H<inf>12</inf>N<inf>2</inf>O<inf>3</inf>)) were solved in monoclinic system with P2<inf>1</inf>/c space group and 3 (C<inf>11</inf>H<inf>9</inf>BrN<inf>2</inf>O<inf>3</inf>) shows concomitant polymorphism and solved in orthorhombic system with Pna2<inf>1</inf> and Pca2<inf>1</inf>. The weak C—H⋯O and C—H…N intermolecular interactions play significant role in crystal packing of 4-Oxo-4H-pyrido[1,2-a]pyrimidine-3-carboxylates. Replacement of methyl group in compound 1 with Bromine atom resulted 3 with increased π…π stacking interactions. The unexpected concomitant polymorphic forms of compounds 3 with details of the crystal structures and supramolecular features are presented. In addition, Hirshfeld surface and 2D fingerprint plots were performed to understand the various intermolecular non-covalent interactions in pyrido[1,2-a]pyrimidine-3-carboxylates.