3,6-Dimethyl-1-phenyl-1H,4H-pyrano[2,3-c]pyrazol-4-one

The title compound, C14H12N2O2, is almost planar with an r.m.s. deviation for all non-H atoms of 0.038 Å. The observed planarity is rationalized in terms of a close intramolecular C—H⋯O interaction. Supramolecular layers, two molecules thick and with a step topology, are formed in the crystal packing via C—H⋯O contacts involving the carbonyl O atom, which accepts two such bonds, and π–π interactions between the components of the fused ring system and the phenyl ring of inversion-related molecules [centroid–centroid distances = 3.6819 (13) and 3.6759 (12) Å].

The title compound, C 14 H 12 N 2 O 2 , is almost planar with an r.m.s. deviation for all non-H atoms of 0.038 Å . The observed planarity is rationalized in terms of a close intramolecular C-HÁ Á ÁO interaction. Supramolecular layers, two molecules thick and with a step topology, are formed in the crystal packing via C-HÁ Á ÁO contacts involving the carbonyl O atom, which accepts two such bonds, andinteractions between the components of the fused ring system and the phenyl ring of inversion-related molecules [centroid-centroid distances = 3.6819 (13) and 3.6759 (12) Å ].

Tiekink Comment
It has been reported that many pyrano[2,3-c]pyrazole derivatives possess analgesic and anti-inflammatory activities (Kuo et al., 1984). In this report, following literature precedents (Gelin et al., 1983;Kuo et al., 1984), the title compound was synthesized, and herein, its crystal and molecular structure are described.
In the title molecule, Fig.1, each of the pyrazole [r.m.s. deviation = 0.001 Å] and pyran-4-one [r.m.s. deviation = 0.006 Å] rings is planar and the dihedral angle between them is 0.82 (11)°. The planarity in the molecule extends to include the pendent phenyl ring, which makes a dihedral angle of 3.17 (11)° with the pyrazole ring. The r.m.s. deviation for the 18 non-hydrogen atoms is 0.038 Å, with maximum deviations of 0.071 (2) Å for atoms C13 and C14, and -0.059 (2) Å for the C10 atom. An explanation for the co-planarity in the molecule is the presence of intramolecular C10-H···O1 and C14-H14···N2 interactions (Table 1).
In the crystal packing, the carbonyl-O2 atom is bifurcated, forming two C-H···O interactions (Table 1 and Fig. 2), leading to a supramolecular layer in the bc plane. Layers are connected into double layers by π-π interactions involving the phenyl ring interacting with both rings of the fused ring system [ring centroid···ring centroid distances = 3.6819 (13) Å, for the five-and six-membered rings, and 3.6759 (12) Å, for the interaction between the two six-membered rings; symmetry operation: -x+2, -y+1, -z+1]. The layers have a step topology and stack along the a axis with no specific intermolecular interactions between them (Fig. 3).
To a solution of dehydroacetic acid (10 mmol) in benzene (20 ml) was added the phenylhydrazine (10 mmol). The mixture was refluxed for 30 min and allowed to stand at room temperature for 2 h. After the mixture was cooled, the hydrazone was collected and recrystallized from ethanol. A solution of this product (10 mmol) in acetic acid (20 ml) was refluxed for 1 h. After evaporation of the solvent, the residue was recrystallized from ethanol as needles. To a solution of this (2.5 g, 0.01 mmol), i.e. 4-acetoacetyl-3-methyl-1-phenyl-2-pyrazolin-5-one, in acetic acid (20 ml) was added concentrated sulfuric acid (1 ml) drop wise. The mixture was poured into cold water (150 ml) and the resulting precipitate was filtered, washed with 5% aqueous Na 2 CO 3 solution, water, dried and recrystallized from ethanol. Yield:

Refinement
Carbon-bound H-atoms were placed in calculated positions and were treated as riding atoms: C-H = 0.95 and 0.98 Å for CH and CH 3 H atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for CH 3 H atoms, and = 1.2 for other H atoms.