Crystal structure of 2-benzylamino-4-(4-bromophenyl)-6,7-dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile

The packing of the title compound features N—H⋯N hydrogen bonds, which form inversion dimers, and weak aromatic π–π stacking interactions.

In the title compound C 22 H 18 BrN 3 , the cyclopentane ring adopts an envelope conformation with the central methylene C atom as the flap. The dihedral angles between the central pyridine ring and the pendant benzyl and and bromobenzene rings are 82.65 (1) and 47.23 (1) , respectively. In the crystal, inversion dimers linked by pairs of N-HÁ Á ÁN n (n = nitrile) hydrogen bonds generate R 2 2 (12) loops. These dimers are linked by weakinteractions [centroidcentroid distance = 3.7713 (14) Å ] into a layered structure.

Chemical context
Cyanopyridine derivatives exhibit useful anticancer and antiviral activities (Cocco et al., 2005;El-Hawash & Abdel Wahab, 2006). 3-Cyanopyridine derivatives have been reported for their wide range of applications such as in their antimicrobial, analgesic, anti-hyperglycemic, antiproliferative and antitumor activities (Brandt et al., 2010;El-Sayed et al., 2011;Ji et al., 2007). As part of our ongoing work in this area, we synthesized the title compound, which contains a pyridine 3-carbonitrile group, and we report herein on its crystal structure.

Structural commentary
The molecular structure of the title compound (I) is shown in Fig. 1. The nitrile atoms C31 and N3 are displaced from the mean plane of the pyridine ring by 0.1016 (1) and 0.1997 (1) Å , respectively. The cyclopentane ring fused with the pyridine ring adopts an envelope conformation with atom C8 as the flap, deviating by 0.3771 (1) Å from the mean plane defined by the other atoms (C5/C6/C7/C9). The amino group is nearly coplanar with the pyridine ring as indicated by the torsion angle N2-C2-C3-C4 = À178.0 (16) . Steric hindrance rotates the benzene ring (C22-C27) out of the plane of the central pyridine ring by 82.65 (1) . This twist may be due to the non-bonded interactions between one of the ortho H atoms of the benzene ring and atom H21B of the CH 2 -NH 2 chain.

Synthesis and crystallization
A mixture of cyclopentanone (1 mmol) 1, 4-bromo benzaldehyde (1 mmol), malononitrile (1 mmol) and benzylamine were taken in ethanol (10 ml) to which p-TSA (1 mmol) was added. The reaction mixture was heated under reflux for 2-3 h. The reaction progress was monitored by thin layer chro- The molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level.

Figure 2
Partial packing diagram of compound (I). For clarity, H atoms bound to atoms not involved in hydrogen bonding are not shown. Table 1 Hydrogen-bond geometry (Å , ).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The NH and C-bound H atoms were placed in calculated positions and allowed to ride on their carrier atoms: N-H = 0.86 Å , C-H = 0.93-0.97 Å , with U iso (H) = 1.5U eq (C) for methyl H atoms and = 1.2U eq (N,C) for other H atoms. The best crystal investigated was of rather poor quality and very weakly diffracting, with no usable data obtained above 49 in 2. Nonetheless, the structure solved readily and refined to give acceptable uncertainties on the metrical data.