N-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-2-phenylacetamide

The title compound, C19H19N3O2, crystallizes with two independent molecules (A and B) in the asymmetric unit. In molecule A, the pyrazole ring adopts a slightly disordered half-chair conformation while in B it is planar [r.m.s. deviation = 0.0386 (15) Å]. The dihedral angle between the mean planes of the two phenyl rings is 56.2 (8) in A and 38.2 (3)° in B. The N-phenyl substituent on the pyrazole ring is twisted by 46.5 (2) in A and 58.6 (4)° in B while the extended phenyl ring is twisted by 82.2 (8) in A and 87.5 (9)° in B. The mean plane of the amide group forms an angle of 74.8 (3) in A and 67.7 (1)° in B with respect to the phenyl ring. In addition, the amide group is rotated by 51.4 (1) in A and 53.6 (2)° in B from the the mean plane of the pyrazole ring. In the crystal, the two molecules are linked via N—H⋯O hydrogen bonds, supported by weak C—H⋯O interactions, forming dimers enclosing an R 2 2(10) ring motif. The dimers are linked via C—H⋯O interactions, forming a three-dimensional structure.

The title compound, C 19 H 19 N 3 O 2 , crystallizes with two independent molecules (A and B) in the asymmetric unit. In molecule A, the pyrazole ring adopts a slightly disordered half-chair conformation while in B it is planar [r.m.s. deviation = 0.0386 (15) Å ]. The dihedral angle between the mean planes of the two phenyl rings is 56.2 (8) in A and 38.2 (3) in B. The N-phenyl substituent on the pyrazole ring is twisted by 46.5 (2) in A and 58.6 (4) in B while the extended phenyl ring is twisted by 82.2 (8) in A and 87.5 (9) in B. The mean plane of the amide group forms an angle of 74.8 (3) in A and 67.7 (1) in B with respect to the phenyl ring. In addition, the amide group is rotated by 51.4 (1) in A and 53.6 (2) in B from the the mean plane of the pyrazole ring. In the crystal, the two molecules are linked via N-HÁ Á ÁO hydrogen bonds, supported by weak C-HÁ Á ÁO interactions, forming dimers enclosing an R 2 2 (10) ring motif. The dimers are linked via C-HÁ Á ÁO interactions, forming a three-dimensional structure.
The title compound, (I), crystallizes with two independent molecules in the asymmetric unit (A and B) ( (C2B/C1B/O1B/N1B) with respect to that of the phenyl rings. In addition, the amide group is rotated by 51.4 (1)° (A), 53.6 (2)° (B) from the the mean plane of the pyrazole rings. Bond lengths are in normal ranges (Allen et al., 1987). N-H···O intermolecular hydrogen bonds supported by a weak C14A-H14A···O1A intermolecular interaction are observed which link the molecules into dimers forming R 2 2 (10) graph set motifs (Fig. 2). Also, additional weak C-H···O intermolecular interactions are also observed which interlink the dimers and influence the crystal packing.

Experimental
Phenylacetic acid (0.136 g, 1 mmol) and 4-aminoantipyrine (0.203 g, 1 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (1.0 g, 0.01 mol) and were dissolved in dichloromethane (20 mL). The mixture was stirred in presence of triethylamine at 273 K for about 3 h. The contents were poured into 100 ml of ice-cold aqueous hydrochloric acid with stirring, which was extracted thrice with dichloromethane. Organic layer was washed with saturated NaHCO 3 solution and brine solution, dried and concentrated under reduced pressure to give the title compound (I). Single crystals were grown from methanol and acetone mixture (1:1) and further recrystallised from ethanol by by the slow evaporation method which were used as such for X-ray studies (M.P.: 445-447 K).

Refinement
All of the H atoms were placed in their calculated positions and then refined using the riding model with Atom-H lengths of 0.93Å (CH); 0.97Å (CH 2 ); 0.96Å (CH 3 ) or 0.86Å (NH). Isotropic displacement parameters for these atoms were set to 1.2 (CH, CH 2 , NH)and 1.5 (CH 3 ) times U eq of the parent atom. Idealised Me refined as rotating group.

Figure 1
ORTEP drawing of (I) (C 19   Molecular packing for (I) viewed along the a axis. Dashed lines indicate N-H···O intermolecular hydrogen bonds supported by a weak C-H···O intermolecular interactions link the molecules into dimers forming R 2 2 (10) graph set motifs. Also, weak C-H···O intermolecular interactions are observed which interlink the dimers and influence the crystal packing. H atoms not involved in hydrogen bonding have been removed for clarity.