2-(4-Chloro-phen-yl)-5-(3,4-dimethoxy-pheneth-yl)-6,7-dihydro-pyrazolo[1,5-a]pyrazin-4(5H)-one.

In the title compound, C(22)H(22)ClN(3)O(3), the dihedral angles between the planes of the benzene rings and the pyrazole ring are 16.05 (10) and 84.84 (10)°. The conformation of the six-membered heterocyclic ring is close to a screw-boat. The crystal packing is stabilized by weak inter-molecular C-H⋯O inter-actions and is also consolidated by C-H⋯π inter-actions.

In the title compound, C 22 H 22 ClN 3 O 3 , the dihedral angles between the planes of the benzene rings and the pyrazole ring are 16.05 (10) and 84.84 (10) . The conformation of the sixmembered heterocyclic ring is close to a screw-boat. The crystal packing is stabilized by weak intermolecular C-HÁ Á ÁO interactions and is also consolidated by C-HÁ Á Á interactions.

Comment
Many pyrazole derivatives are known to exhibit a wide range of biological properties (Farag et al., 2008;Szabó et al., 2008).
As part of our continuing project on the study of the interactions occurring between small molecules and proteins Xie et al., 2008;Zhang et al., 2008), we report here the crystal structure of the title compound.
The molecular structure of the title compound is illustrated in Fig. 1. In contrast to our previously reported structure of a related compound , the conformation of the six-membered heterocyclic ring (N2/N3/C9-C12) in the title compound is close to a screw-boat, with atoms C11 and N3 out of the plane of the remaining four atoms by 0.681 (2) and 0.214 (2) Å, respectively. In the crystal structure, the dihedral angles of the phenyl rings (C1-C6) and (C15-C20) with the pyrazol ring (N1/N2/C7-C9) are 16.05 (10) and 84.84 (10)°, respectively. The crystal packing is stabilized by intermolecular C-H···O interactions and is further consolidated by C-H···π interactions (Table 1).
The product was obtained in 57% yield by column chromatography on silica gel using ethyl acetate as eluent. Crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the solid dissolved in ethyl acetate at room temperature for 5 days.

Refinement
The H atoms were located in difference Fourier maps, their positional and isotropic vibrational parameters were refined freely except for the methyl H-atoms which were included in the refinements at geometrically idealized positions in riding mode with C-H = 0.96 Å and U iso (H) = 1.5 U eq (C). Fig. 1. The molecular structure of the title compound showing displacement ellipsoids drawn at 30% probability level.