Synthesis, crystal structure and Hirshfeld surface analysis of 1,7-dimethyl-5a,6,11a,12-tetra-hydro-benzo[b]benzo[5,6][1,4]oxazino[2,3-e][1,4]oxazine.

Mol-ecules of the title compound, C16H16N2O2, occupy special positions on the twofold rotation axes. The heterocyclic ring adopts a slightly twisted envelope conformation with one of the two junction carbon atoms as the flap. The mean planes through the two halves of the mol-ecule form a dihedral angle of 72.01 (2)°. In the crystal, mol-ecules are linked by pairs of C-H⋯O and N-H⋯C contacts into layers parallel to (100). H⋯H contacts make the largest contribution to the Hirshfeld surface (58.9%). © Çınar et al. 2020.

Chemical context

The title oxazine derivative contains two six-membered heterocyclic rings located between two benzene rings. Oxazine-derived compounds are used in the synthesis of detergents, corrosion inhibitors and industrial dyes (Adib et al., 2006 ▸). This class of mol­ecules has been studied extensively as they exhibit anti­tumor (Sriharsha et al., 2006 ▸), anti­bacterial and anti­fungal (Belz et al., 2013 ▸) activity. Oxazinooxazines are important heterocyclic precursors in the construction of heteropropellanes with applications in material sciences and medicinal chemistry (Dilmaç et al., 2017 ▸). Such heterocycles can be synthesized by several methods (Konstanti­nova et al., 2020 ▸), with the most direct route being the condensation of amino alcohols with either aldehydes or ketones (Hajji et al., 2003 ▸). As the amino and hy­droxy groups are adjacent, 2-amino­phenol readily forms heterocycles. An inter­esting feature of the reaction is the stereo-selective transformation of glyoxal. We report herein the crystal structure and Hirshfeld surface analysis for a new oxazine derivative, 1,7-dimethyl-5a,6,11a,12-tetra­hydro­benzo[b]benzo[5,6][1,4]oxazino[2,3-e][1,4]oxazine.

Structural commentary

The mol­ecular structure of the title compound (I) is shown in Fig. 1 ▸. The mol­ecules occupy special positions on the twofold rotation axes. The heterocyclic ring adopts a slightly twisted envelope conformation with the C8* [symmetry code: (*) −x − 1, y, −z − ] atom as the flap. Except for this atom, the symmetry-independent part of the mol­ecule (C2–C8/O1/N1) is nearly planar, the largest separation from the mean plane being 0.1267 (10) Å for O1. The mean planes of the two halves of the mol­ecule form a dihedral angle of 72.01 (2)°.

Figure 1

The mol­ecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 40% probability level. Starred atoms are generated by the symmetry operation −x − 1, y, −z − .

Supra­molecular features

Surprisingly, no inter­molecular N—H⋯O contacts are observed in the title structure. Instead, C—H⋯O and N—H⋯C contacts are formed, the latter really being of the N—H⋯π type. Pairs of C—H⋯O contacts link the mol­ecules into zigzag chains along [001] (Table 1 ▸, Fig. 2 ▸). Pairs of N—H⋯O contacts also form zigzag chains of mol­ecules along [001] (Table 1 ▸, Fig. 3 ▸). As a result, layers parallel to (100) are formed (Fig. 4 ▸).

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5⋯O1i	0.93	2.59	3.513 (2)	172
N1—H1⋯C5ii	0.86	2.64	3.375 (2)	144

Symmetry codes: (i) ; (ii) .

Figure 2

Chains of the title mol­ecules linked by pairs of C—H⋯O inter­actions.

Figure 3

Chains of mol­ecules linked by pairs of N—H⋯C inter­actions.

Figure 4

Layer of the title mol­ecules linked by C—H⋯O (red) and N—H⋯C (blue) inter­actions.

Hirshfeld surface

The Hirshfeld surfaces were generated using Crystal Explorer 17.5 (Turner et al., 2017 ▸). The d norm mapping was performed in the range of −0.186 to 1.019 arbitrary units. Red spots on the d norm surface (Fig. 5 ▸) indicate regions of C—H⋯O inter­actions. However, the N—H⋯C contacts do not cause red spots on the Hirshfeld surface. Other red spots are due to the H⋯H inter­actions, as can be understood from the fingerprint plot. The characteristic flat surface patches caused by planar stacking are shown in Fig. 6 ▸ a. The shape-index map (Fig. 6 ▸ b) does not contain red and blue triangles related to π–π inter­actions. Fig. 6 ▸ c,d show the d i and d e surfaces, respectively. Fig. 7 ▸ presents the two-dimensional fingerprint plot for the title mol­ecule and those delineated into the specific types of inter­actions. The H⋯H contacts make the largest contribution to the Hirshfeld surface (58.9%). The H⋯C/C⋯H inter­actions are seen at the edges of two-dimensional fingerprint drawings, with a general contribution of 24.6%.

Figure 5

View of the three-dimensional Hirshfeld surface for the title mol­ecule plotted over d norm.

Figure 6

The Hirshfeld surfaces of the title mol­ecule mapped over (a) curvedness, (b) shape-index, (c) d i and (d) d e.

Figure 7

Two-dimensional fingerprint plot for the title mol­ecule (a) and those delineated into the specific types of inter­actions (b–f).

Database survey

A search of the Cambridge Structural Database (CSD, version 5.40, update of August 2019; Groom et al., 2016 ▸) using 1-benzyl-3,4-di­hydro­quinoxalin-2(1H)-one as the main skeleton revealed the presence of four structures similar to the title compound. These are 2,8-di-t-butyl-5a,6,11a,12-tetra­hydro­[1,4]benzoxazino[3,672-b][1,4]benzoxazine (MOYJOC; Niklas et al., 2019 ▸), 5a,6,11a,12-tetra­hydro­[1,4]benz­oxa­zino[3,2-b][1,4]benzoxazine (FIGVOG; Tauer et al., 1986 ▸), 5a,6,11a,12-tetra­hydro-5a,11a-dimethyl-1,4-benzoxazino[3,2-b][1,4]benzoxazine (ABEQAA; Hai-Yan et al., 2004 ▸) and N,N′-di-5a,6,11a,12-tetra­hydro­[1,4]benzoxazino[3,2]benzoxazine (BAJNIJ; Farfán et al., 1992 ▸). In the structures MOYJOC and FIGVOG, the dihedral angles between the two approximately planar halves of the mol­ecule [67.11 (3) and 64.28 (2)°, respectively] are smaller than in (I). In MOYJOC, both NH groups are involved in hydrogen bonds with the heterocyclic oxygen atoms. In FIGVOG, only one NH group takes part in such hydrogen bonding, while the other makes an N—H⋯C contact similar to that observed in (I). In ABEQAA, the hydrogen atoms at the bridge C atoms (C8 and C8* in the title mol­ecule) are replaced by methyl groups. As a result, the dihedral angle increases to 81.70 (2)°. In this structure, both NH groups form weak inter­molecular N—H⋯O hydrogen bonds.

Synthesis and crystallization

To a solution of 2-amino-3-methyl­phenol (21.8 mg, 0.177 mmol) in ethanol (20 ml), was added glyoxal (40 wt % solution in H2O) (12.8 mg, 0.089 mmol) dissolved in ethanol (20 ml) and the mixture was refluxed for 12 h. The orange product obtained was washed with ether and recrystallized from ethanol at room temperature (m.p. 472-475 K, yield 67%).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. All hydrogen atoms were constrained to ride on their parent atoms with C—H = 0.93, 0.96 and 0.98 Å for aromatic, methyl and methine H atoms, respectively, and with N—H = 0.86 Å. Isotropic displacement parameters of these atoms were constrained to 1.5U eq(C) for the methyl group and to 1.2U eq(C,N) for all other H atoms.

Table 2

Experimental details

Crystal data
Chemical formula	C16H16N2O2
M r	268.31
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	296
a, b, c (Å)	24.798 (3), 4.7133 (4), 11.5330 (14)
β (°)	106.751 (9)
V (Å3)	1290.8 (3)
Z	4
Radiation type	Mo Kα
μ (mm−1)	0.09
Crystal size (mm)	0.78 × 0.42 × 0.13
Data collection
Diffractometer	Stoe IPDS 2
Absorption correction	Integration (X-RED32; Stoe & Cie, 2002 ▸)
T min, T max	0.941, 0.989
No. of measured, independent and observed [I > 2σ(I)] reflections	5580, 2194, 1024
R int	0.059
(sin θ/λ)max (Å−1)	0.745
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.049, 0.134, 0.88
No. of reflections	2194
No. of parameters	92
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.15, −0.16

Computer programs: X-AREA and X-RED32 (Stoe & Cie, 2002 ▸), SHELXT2018/3 (Sheldrick, 2015a ▸), SHELXL2018/3 (Sheldrick, 2015b ▸), OLEX2 (Dolomanov et al., 2009 ▸), Mercury (Macrae et al., 2020 ▸), WinGX (Farrugia, 2012 ▸), PLATON (Spek, 2020 ▸) and publCIF (Westrip, 2010 ▸).

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989020010646/yk2135sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989020010646/yk2135Isup4.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S2056989020010646/yk2135Isup3.cml

CCDC reference: 2021045

Additional supporting information: crystallographic information; 3D view; checkCIF report

C16H16N2O2	Dx = 1.381 Mg m−3
Mr = 268.31	Melting point = 472–475 K
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 24.798 (3) Å	Cell parameters from 3858 reflections
b = 4.7133 (4) Å	θ = 1.8–32.0°
c = 11.5330 (14) Å	µ = 0.09 mm−1
β = 106.751 (9)°	T = 296 K
V = 1290.8 (3) Å3	Plate, orange
Z = 4	0.78 × 0.42 × 0.13 mm
F(000) = 568

Stoe IPDS 2 diffractometer	2194 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus'	1024 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.059
Detector resolution: 6.67 pixels mm-1	θmax = 32.0°, θmin = 3.4°
rotation method scans	h = −35→36
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)	k = −7→6
Tmin = 0.941, Tmax = 0.989	l = −16→16
5580 measured reflections

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.134	H-atom parameters constrained
S = 0.88	w = 1/[σ2(Fo2) + (0.0639P)2] where P = (Fo2 + 2Fc2)/3
2194 reflections	(Δ/σ)max < 0.001
92 parameters	Δρmax = 0.15 e Å−3
0 restraints	Δρmin = −0.16 e Å−3

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.

	x	y	z	Uiso*/Ueq
O1	−0.50672 (4)	0.7122 (2)	−0.13429 (9)	0.0582 (3)
N1	−0.57174 (5)	0.4629 (3)	−0.34733 (13)	0.0622 (4)
H1	−0.591648	0.369876	−0.409012	0.075*
C7	−0.59760 (6)	0.6173 (3)	−0.27650 (13)	0.0484 (3)
C2	−0.65643 (6)	0.6435 (3)	−0.30692 (14)	0.0531 (4)
C6	−0.56462 (6)	0.7472 (3)	−0.17100 (13)	0.0497 (3)
C8	−0.51247 (6)	0.4590 (3)	−0.31772 (14)	0.0545 (4)
H8	−0.500090	0.289696	−0.352275	0.065*
C3	−0.67936 (7)	0.8104 (4)	−0.23575 (17)	0.0657 (5)
H3	−0.718296	0.828025	−0.255126	0.079*
C5	−0.58834 (7)	0.9190 (3)	−0.10285 (15)	0.0599 (4)
H5	−0.565754	1.011706	−0.034970	0.072*
C1	−0.69244 (7)	0.4830 (4)	−0.41332 (17)	0.0675 (5)
H1A	−0.682704	0.536853	−0.485013	0.101*
H1B	−0.731357	0.526107	−0.423392	0.101*
H1C	−0.686334	0.283070	−0.399720	0.101*
C4	−0.64605 (8)	0.9525 (4)	−0.13620 (18)	0.0709 (5)
H4	−0.662501	1.070905	−0.091513	0.085*

	U11	U22	U33	U12	U13	U23
O1	0.0456 (6)	0.0679 (7)	0.0562 (6)	−0.0052 (4)	0.0068 (5)	−0.0074 (5)
N1	0.0411 (7)	0.0735 (8)	0.0664 (8)	−0.0036 (6)	0.0067 (6)	−0.0223 (7)
C7	0.0436 (7)	0.0457 (7)	0.0545 (8)	−0.0027 (6)	0.0122 (6)	0.0014 (6)
C2	0.0435 (7)	0.0526 (8)	0.0612 (9)	−0.0031 (6)	0.0120 (7)	0.0087 (7)
C6	0.0449 (7)	0.0509 (7)	0.0534 (8)	−0.0046 (6)	0.0146 (6)	0.0049 (7)
C8	0.0429 (7)	0.0554 (8)	0.0621 (9)	0.0023 (6)	0.0101 (7)	−0.0047 (7)
C3	0.0487 (9)	0.0707 (10)	0.0806 (12)	0.0037 (8)	0.0234 (9)	0.0044 (9)
C5	0.0648 (10)	0.0610 (9)	0.0565 (9)	−0.0076 (7)	0.0214 (7)	−0.0040 (7)
C1	0.0450 (8)	0.0771 (10)	0.0726 (11)	−0.0070 (7)	0.0044 (7)	0.0036 (9)
C4	0.0669 (11)	0.0733 (11)	0.0811 (12)	0.0031 (8)	0.0349 (10)	−0.0104 (10)

O1—C6	1.3846 (17)	C8—C8i	1.505 (3)
O1—C8i	1.4521 (18)	C8—H8	0.9800
N1—C7	1.3822 (19)	C3—C4	1.379 (3)
N1—C8	1.4099 (19)	C3—H3	0.9300
N1—H1	0.8600	C5—C4	1.380 (2)
C7—C6	1.397 (2)	C5—H5	0.9300
C7—C2	1.4041 (19)	C1—H1A	0.9600
C2—C3	1.373 (2)	C1—H1B	0.9600
C2—C1	1.498 (2)	C1—H1C	0.9600
C6—C5	1.373 (2)	C4—H4	0.9300
C6—O1—C8i	113.95 (11)	O1i—C8—H8	109.8
C7—N1—C8	119.51 (12)	C8i—C8—H8	109.8
C7—N1—H1	120.2	C2—C3—C4	121.60 (15)
C8—N1—H1	120.2	C2—C3—H3	119.2
N1—C7—C6	119.38 (12)	C4—C3—H3	119.2
N1—C7—C2	121.63 (14)	C6—C5—C4	119.27 (16)
C6—C7—C2	118.98 (14)	C6—C5—H5	120.4
C3—C2—C7	118.72 (15)	C4—C5—H5	120.4
C3—C2—C1	121.82 (14)	C2—C1—H1A	109.5
C7—C2—C1	119.43 (15)	C2—C1—H1B	109.5
C5—C6—O1	118.20 (13)	H1A—C1—H1B	109.5
C5—C6—C7	121.14 (13)	C2—C1—H1C	109.5
O1—C6—C7	120.64 (12)	H1A—C1—H1C	109.5
N1—C8—O1i	109.28 (12)	H1B—C1—H1C	109.5
N1—C8—C8i	109.82 (15)	C3—C4—C5	120.05 (16)
O1i—C8—C8i	108.29 (9)	C3—C4—H4	120.0
N1—C8—H8	109.8	C5—C4—H4	120.0
C8—N1—C7—C6	−5.4 (2)	N1—C7—C6—O1	−2.8 (2)
C8—N1—C7—C2	175.60 (14)	C2—C7—C6—O1	176.19 (13)
N1—C7—C2—C3	−177.10 (14)	C7—N1—C8—O1i	−82.21 (17)
C6—C7—C2—C3	3.9 (2)	C7—N1—C8—C8i	36.44 (15)
N1—C7—C2—C1	4.7 (2)	C7—C2—C3—C4	0.3 (2)
C6—C7—C2—C1	−174.29 (14)	C1—C2—C3—C4	178.44 (16)
C8i—O1—C6—C5	159.07 (13)	O1—C6—C5—C4	−178.67 (14)
C8i—O1—C6—C7	−22.75 (17)	C7—C6—C5—C4	3.2 (2)
N1—C7—C6—C5	175.29 (14)	C2—C3—C4—C5	−2.9 (3)
C2—C7—C6—C5	−5.7 (2)	C6—C5—C4—C3	1.1 (2)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O1ii	0.93	2.59	3.513 (2)	172
N1—H1···C5iii	0.86	2.64	3.375 (2)	144

Parameters	Å, °
O1—C6	1.3846 (17)
O1—C8*	1.4521 (18)
N1—C8	1.4099 (19)
N1—C7	1.3822 (19)
C8—C8*	1.505 (3)
C6—C7	1.397 (2)
O1*—C8—C8*	108.29 (9)
N1—C8—C8*	109.82 (15)
N1—C8—O1*	109.28 (12)
C6—O1—C8*	113.95 (11)
C7—N1—C8—C8*	36.44 (15)
C8*—O1—C6—C7	-22.75 (17)
C2—C7—C6—C5	-5.7 (2)
N1—C7—C6—O1	-2.8 (2)