Weak hydrogen bonding in the structures of three double-acylated aminoantipyrines

The structures of three doubly-acylated 4-aminoantipyrine (AP) compounds where the aryl substituent is varied are reported and analysed in terms of their relative conformation, intermolecular interactions and overall packing; these are N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-4-methyl-N-[(4-methylphenyl)carbonyl]benzamide, C₂₇H₂₅N₃O₃, N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-N-[(furan-2-yl)carbonyl]furan-2-carboxamide, C₂₁H₁₇N₃O₅, and N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-N-[(thiophen-2-yl)carbonyl]thiophene-2-carboxamide, C₂₁H₁₇N₃O₃S₂. The compounds were crystallized using the encapsulated nanodroplet crystallization (ENaCt) protocol. Where previous singly-acylated AP compounds produced structures with obvious classical hydrogen-bonding motifs, the doubly-acylated derivatives lack classical donors and therefore exhibit weak C-H hydrogen bonds and interactions involving the π-system. All three AP compounds form bifurcated C-H...O interactions having either dimer or chain motifs, with the other structure-directing interactions being dependant on the nature of the aryl substituent.