Molecular conformation and supramolecular aggregation in two fused pyrazoles:: π-stacked R22(6) dimers in 2,8,8-trimethyl-6,7,8,9-tetrahydro-pyrazolo[2,3-a]quinazolin-6-one, and sheets of alternating R22(12) and R66(48) rings in 3-tert-butyl-4′,4′-dimethyl-1-phenyl-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-spiro-1′-cyclohexane-2′,6′-dione

In 2,8,8-trimethyl-6,7,8,9-tetrahydropyrazolo[2,3-a]quinazolin-6-one, C13H15N3O, (I), the heterobicyclic system is planar and exhibits peripheral ten pi-electron delocalization. In 3-tert-butyl-4',4'-dimethyl-1-phenyl-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-spiro-1'-cyclohexane-2',6'-dione, C23H25N3O2, (II), the pyrazole ring exhibits marked bond fixation, while the reduced pyridine ring adopts a half-chair conformation. Molecules of (I) are linked into centrosymmetric R-2(2)(6) dimers by a single C-H...N hydrogen bond [H...N = 2.50 Angstrom, C...N = 3.3397 (17) Angstrom and C-H...N = 148degrees], and these dimers are linked into chains by a single pi-pi stacking interaction. In (II), the combined action of one N-H...O hydrogen bond [H...O = 2.40 Angstrom, N...O = 3.2248 (15) Angstrom and N-H...O = 157degrees] and one C-H...O hydrogen bond [H...O = 2.48 Angstrom, C...O = 3.407 (2) Angstrom and C-H...O = 164degrees] links the molecules into sheets built from alternating centrosymmetric R-2(2)(12) and R-6(6)(48) rings; there is a weak C-H...N interaction [H...N = 2.60 Angstrom, C...N = 3.5149 (18) Angstrom and C-H...N = 154degrees] between molecules in adjacent sheets.