Molecular conformation and supramolecular aggregation in two fused pyrazoles: π‐stacked R (6) dimers in 2,8,8‐trimethyl‐6,7,8,9‐tetrahydropyrazolo[2,3‐ a ]quinazolin‐6‐one, and sheets of alternating R (12) and R (48) rings in 3‐ tert ‐butyl‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1 H ‐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, C 13 H 15 N 3 O, (I), the heterobicyclic system is planar and exhibits peripheral ten π‐electron delocalization. In 3‐ tert ‐butyl‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1 H ‐ pyrazolo[3,4‐ b ]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C 23 H 25 N 3 O 2 , (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 (6) dimers by a single C—H⋯N hydrogen bond [H⋯N = 2.50 Å, C⋯N = 3.3397 (17) Å and C—H⋯N = 148°], and these dimers are linked into chains by a single π–π stacking interaction. In (II), the combined action of one N—H⋯O hydrogen bond [H⋯O = 2.40 Å, N⋯O = 3.2248 (15) Å and N—H⋯O = 157°] and one C—H⋯O hydrogen bond [H⋯O = 2.48 Å, C⋯O = 3.407 (2) Å and C—H⋯O = 164°] links the molecules into sheets built from alternating centrosymmetric (12) and (48) rings; there is a weak C—H⋯N interaction [H⋯N = 2.60 Å, C⋯N = 3.5149 (18) Å and C—H⋯N = 154°] between molecules in adjacent sheets.