3-Cyano-6-hydroxy-4-methyl-2-pyridone: two new pseudopolymorphs and two cocrystals with products of an in situ nucleophilic aromatic substitution

Four crystal structures of 3-cyano-6-hydroxy-4-methyl-2-pyridone (CMP), viz. the dimethyl sulfoxide monosolvate, C7H6N2O2 center dot C2H6OS, (1), the N,N-dimethylacetamide monosolvate, C7H6N2O2 center dot C4H9NO, (2), a cocrystal with 2-amino-4-dimethylamino-6-methylpyrimidine (as the salt 2-amino-4-dimethylamino-6-methylpyrimidin-1-ium 5-cyano-4-methyl-6-oxo-1,6-dihydropyridin-2-olate), C7H13N4+center dot C7H5N2O2-, (3), and a cocrystal with N, N-dimethylacetamide and 4,6-diamino-2-dimethylamino-1,3,5-triazine [as the solvated salt 2,6-diamino-4-dimethylamino-1,3,5-triazin-1-ium 5-cyano-4-methyl-6-oxo-1,6-dihydropyridin-2-olate-N,N-dimethylacetamide (1/1)], C5H11N6+center dot C7H5N2O2-center dot C4H9NO, (4), are reported. Solvates (1) and (2) both contain the hydroxy group in a para position with respect to the cyano group of CMP, acting as a hydrogen-bond donor and leading to rather similar packing motifs. In cocrystals (3) and (4), hydrolysis of the solvent molecules occurs and an in situ nucleophilic aromatic substitution of a Cl atom with a dimethylamino group has taken place. Within all four structures, an R-2(2)(8) N-H center dot center dot center dot O hydrogen-bonding pattern is observed, connecting the CMP molecules, but the pattern differs depending on which O atom participates in the motif, either the ortho or para O atom with respect to the cyano group. Solvents and coformers are attached to these arrangements via single-point O-H center dot center dot center dot O interactions in (1) and (2) or by additional R-4(4)(16) hydrogen-bonding patterns in (3) and (4). Since the in situ nucleophilic aromatic substitution of the coformers occurs, the possible Watson-Crick C-G base-pair-like arrangement is inhibited, yet the cyano group of the CMP molecules participates in hydrogen bonds with their coformers, influencing the crystal packing to form chains.