1-Phenyl-6,7,8,9-hexahydro-1H,5H-cyclohepta[1′,2′:2,3]pyrido[6,5-c]pyrazol-4-amine: a new tacrine analogue

The title compound, C17H18N4, contains a pyrazolopyridine system fused with a seven-membered carbocyclic ring. The pyrazole ring is coplanar with the pyridine ring, while the phenyl ring is twisted by a dihedral angle of 14.38 (14)° with respect to the pyridine ring. The seven-membered ring displays a chair conformation. The packing is stabilized by N—H⋯N hydrogen bonds and N—H⋯π(arene) interactions.

The title compound, C 17 H 18 N 4 , contains a pyrazolopyridine system fused with a seven-membered carbocyclic ring. The pyrazole ring is coplanar with the pyridine ring, while the phenyl ring is twisted by a dihedral angle of 14.38 (14) with respect to the pyridine ring. The seven-membered ring displays a chair conformation. The packing is stabilized by N-HÁ Á ÁN hydrogen bonds and N-HÁ Á Á(arene) interactions.
In the title compound, the fused pyrazolopyridine moiety is roughly coplanar, with an angle of 1.4° between the pyrazole and the pyridine rings ( Fig. 1), The largest deviation from the mean plane being 0.014 (2) There are strong intermolecular N-H···N hydrogen bonds between the amino group and one N atom of the pyrazole ring (Table 1, Fig. 2). The packing is further stabilized by N-H···π(benzene) interactions (Table 1).

Experimental
A solution of 0.2 g of 5-amino-4-cyanopyrazole (1.1 mmol,), 0.16 g of AlCl 3 (1.2 mmol,) in 5 ml of 1,2-dichloroethane was refluxed for 4 h (monitored by TLC). The reaction mixture was cooled, dispersed into THF/water (2:1 vol.) and titrated to pH=7 by 20% sodium hydroxide. Then, the mixture was stirred for 30 min. and extracted three times with dichloromethane, the organic layers were dried and evaporated at reduced pressure to give the solid product (Fig. 3). The title compound 1 was purified by silica gel column chromatography eluting with ethyl acetate/light petroleum in 40% yield.
Its single-crystal was cultured from a solution of ethanol by slow evaporation at room temperature.  ,6.52;N,20.13. Found: C,73.17;H,6.52;N,19.99.

Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.93 Å (aromatic) or 0.98 Å (methine) with U iso (H) = 1.2U eq (C). H atoms attached to N were located in difference Fourier maps but introduced in calculated positions and treated as riding on the N atoms with N-H = 0.86 Å and U iso (H) = 1.2U eq (N). Fig. 1. The molecular structure of the title compound, with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are represented as small spheres of arbitrary radii.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.