Unusual formation of (E)-11-(aminomethylene)-8,9,10,11-tetrahydropyrido[2′,3′:4,5]pyrimido[1,2-a]azepin-5(7H)-one and its crystal structure

Unusual formation of (E)-11-(aminomethylene)-8,9,10,11-tetrahydro-pyrido[2′,3′:4,5]pyrimido[1,2-a]azepin-5(7H)-one was found at formylation of 8,9,10,11-tetrahydropyrido[2′,3′:4,5]pyrimido[1,2-a]-azepin-5(7H)-one, which was explained by re-amination of firstly formed intermediate.


Chemical context
Pyrimidine-containing heterocyclic compounds are widely distributed in nature (Lagoja, 2005) and among synthetic compounds (Joshi et al., 2016;Roopan & Sompalle, 2016). These compounds are of theoretical and practical interest, having plural reactivity and with many prospective biologically active compounds among the synthesized derivatives.

Structural commentary
The title compound crystallizes in the centrosymmetric monoclinic P2 1 /c (No. 14) space group. The asymmetric unit contains one crystallographically independent molecule. A displacement ellipsoid plot showing the atom-numbering scheme is presented in Fig. 2. In the molecule, the sevenmembered pentamethylene ring exhibits a twist-boat conformation and has an approximate twofold symmetry with a C 2 axis passing through atom C12 and midpoint of the C2-C9 bond. The amino group is E-oriented and hybridization of the N atom in this group lies between sp 3 and sp 2 . The C-N bond makes an angle of 155 with the bisector of the H-N-H angle. The equivalent angle in methylamine with a pyramidal sp 3 -hybridized N atom is $123 (Klingebiel et al., 2002) and it is nearly 180 in formamide with a planar sp 2 -hybridized N atom (Gajda & Katrusiak, 2011). The pyrimidine ring is twisted slightly, which may be because of the influence of the twisted seven-membered azepane ring. The N1-C8A-N4A-C4 torsion angle of is 8.7 (4) .

Synthesis and crystallization
Materials and methods. The results of electro spray ionization mass spectrometry (ESI-MS) were recorded using a 6420 TripleQuadLC/MC (Agilent Technologies, US) LC-MS spectrometer. The measurements were carried out in positive-ion mode. 1 H NMR spectra were recorded in CD 3 OD on a Varian 400-MR spectrometer operating accordingly at 400 MHz. Hexamethyldisiloxcane (HMDSO) was used as internal standard and the chemical shift of 1 H was recorded in ppm. Melting points were measured on a Boetius and MEL-TEMP apparatus manufactured by Branstead international (USA) and are uncorrected. IR spectra were recorded on an IR Fourier System 2000 (Perkin-Elmer) as KBr pellets.
The reaction process was monitored by TLC on Silufol UV-254 plates using a CHCl 3 /CH 3 OH (12:1) solvent system and the developed plates were visualized under a UV lamp. Solvents were purified by standard procedures. Organic solutions were dried over anhydrous Na 2 SO 4 or with dried CaCl 2 .

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H-bound N atoms were freely refined. C-bound H atoms were refined as riding with C-H = 0.93 or 0.97 Å and U iso (H) = 1.2U eq (C). Hydrogen-bonded chain formation in 3.  (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL2014/7 (Sheldrick, 2015). 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.

Funding information
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )