Crystal structure of 1-amino-2-oxo-2,5,6,7,8,9-hexahydro-1H-cyclohepta[b]pyridine-3-carbonitrile

In the title compound the seven-membered ring adopts a conformation such that the three atoms not involved in the aromatic plane lie on the same side of that plane. One hydrazinic H atom forms an intramolecular hydrogen bond to the O atom; the other forms a classical intermolecular hydrogen bond N—H⋯O, which combines with a ‘weak’ Har⋯O interaction to build up double layers of molecules parallel to the bc plane.

In the title compound, C 11 H 13 N 3 O, the seven-membered ring adopts a conformation such that the three atoms not involved in the aromatic plane lie on the same side of that plane. One hydrazinic H atom forms an intramolecular hydrogen bond to the O atom; the other forms a classical intermolecular hydrogen bond N-HÁ Á ÁO, which combines with a 'weak' H ar Á Á ÁO interaction to build up double layers of molecules parallel to the bc plane.

Chemical context
We have recently described various novel approaches for the synthesis of a new class of N-substituted amino derivatives of pyridines and pyrimidines (Elgemeie, Salah et al., 2015;Elgemeie et al., 2016). These compounds are important as pyrimidine ring systems that are not nucleoside analogs, and are interesting as antimetabolic agents (Elgemeie & Hamed, 2014;Elgemeie & Abd Elaziz, 2015). They have a greater selectivity for a broader range of human tumors, hence our interest in this class of compounds (Elgemeie, Abou-Zeid et al., 2015;. We report here a novel one-step synthesis of a cycloheptane-ring-fused N-amino-2-pyridone derivative by reaction of the sodium salt of 2-(hydroxymethylene)-1cycloheptanone (1) with a cyanoacetohydrazide (2). Thus, (1) reacted with (2) in piperidine acetate to give a product of molecular formula C 11 H 13 N 3 O (M + = 203), for which two isomeric structures, (3) and (4), seemed possible, corresponding to two possible modes of cyclization. Spectroscopic data cannot differentiate between these structures, and therefore the crystal structure was determined, confirming the exclusive presence of tautomer (3) in the solid state. The formation of (3) from the reaction of (1) and (2) is assumed to proceed via initial addition of the active methylene carbon atom of (2) to the formyl group of (1) to give the favoured, kinetically controlled product (3). The 1 H NMR spectra of the product revealed the presence of an N-NH 2 group at = 6.4 p.p.m. and a pyridine H-4 at 7.8 p.p.m. in solution.

Structural commentary
The structure of the title compound is shown in Fig. 1   The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The intramolecular N-HÁ Á ÁO hydrogen bond is shown as a dashed line (see Table 1)
2-pyridones (with an unsubstituted NH function in the ring) was published by Fischer et al. (2004). The seven-membered ring adopts a conformation such that all three atoms C6, C7 and C8 lie to the same side of the plane formed by the pyridone ring together with C5 and C9; the respective deviations from this plane are 1.480 (2), 1.616 (3) and 1.470 (2) Å .

Supramolecular features
The classical hydrogen-bond donor N1-H01 is only involved in intramolecular hydrogen bonding ( Fig. 1 and Table 1). The second such donor N1-H02 forms a classical hydrogen bond to the acceptor O1 of a neighbouring molecule related by the 2 1 screw axis. Additionally, the 'weak' but quite short hydrogen bond C4-H4Á Á ÁO1 links molecules related by the c glide plane. The overall effect is to build up double layers of molecules ( Fig. 2 (Albov et al., 2004a,b) and QAHLOB (Fischer et al., 2004).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The NH hydrogens were located in a difference Fourier map and freely refined. The C-bound H atoms were included using a riding model starting from calculated positions: C-H = 0.95-0.99 Å with U iso (H) = 1.2U eq (C).  (Siemens, 1994); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

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. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 8.5275 (0.0007) x + 0.7466 (0.0052) y -3.3783 (0.0058) z = 0.3993 (0.0040) * -0.0117 (0.0008) N1 * 0.0031 (0.0009) C2 * 0.0072 (0.0009) C3 * -0.0090 (0.0009) C4 * 0.0007 (0.0009) C4A * 0.0097 (0.0009) C9A 1.4803 (0.0024) C6 1.6155 (0.0026) C7 1.4700 (0.0023) C8 Rms deviation of fitted atoms = 0.0079 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 > 2sigma(F 2 ) is used only for calculating R-factors(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.