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Crystal structure of 1,2-bis­­(6-bromo-3,4-di­hydro-2H-benz[e][1,3]oxazin-3-yl)ethane: a bromine-containing bis-benzoxazine

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aUniversidad Nacional de Colombia, Sede Bogotá, Facultad de Ciencias, Departamento de Química, Cra 30 No. 45-03, Bogotá, Código Postal 110911, Colombia, and bInstitut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von Laue-Str., 7, 60438 Frankfurt/Main, Germany
*Correspondence e-mail: ariverau@unal.edu.co

Edited by J. Simpson, University of Otago, New Zealand (Received 13 October 2016; accepted 16 October 2016; online 25 October 2016)

The title benzoxazine molecule, C18H18Br2N2O2, was prepared by a Mannich-type reaction of 4-bromo­phenol with ethane-1,2-di­amine and formaldehyde. The title compound crystallizes in the monoclinic space group C2/c with a centre of inversion located at the mid-point of the C—C bond of the central CH2CH2 spacer. The oxazinic ring adopts a half-chair conformation. The structure is compared to those of other functionalized benzoxazines synthesized in our laboratory. In the crystal, weak C—H⋯Br and C—H⋯O hydrogen bonds stack the mol­ecules along the b-axis direction.

1. Chemical context

In a continuation of our work on the synthesis and characterization of bis-1,3-benzoxazines, we have studied some of the chemical properties and determined the crystal structure of the title compound. Benzoxazines form an important class of benzo-fused heterocycles with a wide spectrum of biological activities. They are also emerging as desirable phenolic resin precursors because benzoxazines can undergo ring opening without emitting volatile materials during the curing process. This leads to a final cured product with excellent properties (Pilato, 2010[Pilato, L. (2010). Resin Chemistry In Phenolic Resins: A Century of Progress, edited by L. Pilato, pp. 41-91. Berlin Heidelberg: Springer-Verlag.]). Normally, the incorporation of bromine can increase the flame-retarding properties and reduce the flammability of polymers (Li, et al., 2010[Li, S., Huang, W., Liu, X., Yu, X. & Xiao, W. (2010). Polym. Adv. Technol. 21, 229-234.]). Recently, we have investigated the crystal structures of analogous bifunctional benzoxazines namely 3,3′-(ethane-1,2-di­yl)bis­(6-substituted-3,4-di­hydro-2H-1,3-benzoxazine) (Rivera et al., 2010[Rivera, A., Rojas, J. J., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o1134.], 2011[Rivera, A., Camacho, J., Ríos-Motta, J., Pojarová, M. & Dušek, M. (2011). Acta Cryst. E67, o2028.], 2012a[Rivera, A., Camacho, J., Ríos-Motta, J., Fejfarová, K. & Dušek, M. (2012a). Acta Cryst. E68, o148.],b[Rivera, A., Camacho, J., Ríos-Motta, J., Kučeraková, M. & Dušek, M. (2012b). Acta Cryst. E68, o2734.]) that were prepared to investigate whether replacement of the substituents at the para position of the phenyl ring affects the electrophilic anomeric effect in the N–C–O sequence of the adjacent oxazine ring. In addition, as benzoxazine contains a tertiary nitro­gen atom, the lone-pair electrons may play an important role in the inter­action with guest mol­ecules but there are no reports on the inclusion properties of polybenzoxazines (Chirachanchai et al., 2011[Chirachanchai, S., Phongtamrug, S. & Tashiro, K. (2011). Supramolecular Chemistry of Benzoxazines: From Simple, Selective, Effective, and Efficient Macrocyclization Pathways to Host-Guest Properties. In Handbook of Benzoxazine Resins, pp 331-352. Amsterdam: Elsevier.]). An X-ray structural study may therefore provide a better understanding of the ability of benzoxazines to act as novel host–guest compounds. In our opinion, the title compound also has potential applications in the production of new bromine-containing phenolic resins.

2. Structural commentary

The asymmetric unit of the title compound (Fig. 1[link]), C18H18Br2N2O2, contains one half of the organic mol­ecule, an inversion centre generates the other half of the mol­ecule (symmetry operation: 1 − x, 1 − y, 1 − z). The six-membered oxazine heterocyclic ring adopts a half-chair conformation, with puckering parameters Q = 0.512 (2) Å, θ =129.6 (2)°, φ = 283.6 (3)°. This ring is analysed with respect to the plane formed by O1/C3/C4/C5, with deviations of the C2 and N1 atoms from this plane of 0.300 (6) and −0.320 (4) Å, respectively.

[Scheme 1]
[Figure 1]
Figure 1
The mol­ecular structure of the title compound, Displacement ellipsoids are drawn at the 50% probability level. Atoms labelled with the suffix A are generated using the symmetry operator (1 − x, 1 − y, 1 − z).

The C—C bond distances and angles of the aromatic rings were found to be normal. The C3—O1 bond length [1.372 (6) Å] is comparable with other previously reported C—O bond lengths for related structures [1.370 (10) and 1.388 (9) Å (Rivera et al., 2012a[Rivera, A., Camacho, J., Ríos-Motta, J., Fejfarová, K. & Dušek, M. (2012a). Acta Cryst. E68, o148.]) and 1.376 (1) Å (Rivera et al., 2011[Rivera, A., Camacho, J., Ríos-Motta, J., Pojarová, M. & Dušek, M. (2011). Acta Cryst. E67, o2028.])], but is found to be shorter in the p-chloro derivative where C—O = 1.421 (2) Å (Rivera et al., 2010[Rivera, A., Rojas, J. J., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o1134.]). Inter­estingly, the C2—N1 and C2—O1 distances, 1.450 (5) and 1.456 (6) Å, respectively, are significantly different from the corresponding distances in the p-chloro derivative [1.369 (2) and 1.529 (2) Å, respectively; Rivera et al., 2010[Rivera, A., Rojas, J. J., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o1134.]]. Indeed, the values observed here are closer to those found in the analogous compound with no p-substituent on the aromatic ring (1.424 and 1.463 Å, respectively; Rivera et al., 2012a[Rivera, A., Camacho, J., Ríos-Motta, J., Fejfarová, K. & Dušek, M. (2012a). Acta Cryst. E68, o148.]). This may indicate that the presence of the electron-withdrawing bromine atom does not significantly affect the adjacent oxazinic ring.

3. Supra­molecular features

In the crystal, weak C5—H5B⋯Br1 hydrogen bonds (Table 1[link]) lead to the formation of inversion dimers with R22(12) ring motifs. These combine with the inversion symmetry of the mol­ecule to produce chains of mol­ecules along the c axis. Additional weak C2—H2B⋯O1 hydrogen bonds link these chains, stacking mol­ecules along the b-axis direction, Fig. 2[link].

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C5—H5B⋯Br1i 0.99 3.04 3.951 (5) 154
C2—H2B⋯O1ii 0.99 2.64 3.506 (6) 146
Symmetry codes: (i) [-x+1, y, -z+{\script{3\over 2}}]; (ii) [-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}].
[Figure 2]
Figure 2
Packing diagram for the title compound, viewed along the b axis, with hydrogen bonds drawn as dashed lines.

4. Database survey

A database search yielded four comparable structures, namely 3,3′-(ethane-1,2-di­yl)bis­(6-methyl-3,4-di­hydro-2H-1,3-benzoxazine) (AXAKAM; Rivera et al., 2011[Rivera, A., Camacho, J., Ríos-Motta, J., Pojarová, M. & Dušek, M. (2011). Acta Cryst. E67, o2028.]), 3,3′-ethyl­enebis(3,4-di­hydro-6-chloro-2H-1,3-benzoxazine), (NUQKAM; Rivera et al., 2010[Rivera, A., Rojas, J. J., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o1134.]), 3,3′-(ethane-1,2-di­yl)bis­(6-meth­oxy-3,4-di­hydro-2H-1,3-benzoxazine) monohydrate (QEDDOU; Rivera et al., 2012b[Rivera, A., Camacho, J., Ríos-Motta, J., Kučeraková, M. & Dušek, M. (2012b). Acta Cryst. E68, o2734.]), 3,3′-(ethane-1,2-di­yl)bis­(3,4-di­hydro-2H-1,3-benzoxazine) (SAGPUN; Rivera et al., 2012a[Rivera, A., Camacho, J., Ríos-Motta, J., Fejfarová, K. & Dušek, M. (2012a). Acta Cryst. E68, o148.]). The Cl-substituted compound (NUQKAM) and the title compound are isomorphous. However, AXAKAM and SAGOUN have different space groups and in QEDDOU a solvent water mol­ecule is included in the crystal packing.

5. Synthesis and crystallization

An aqueous solution of formaldehyde (1.5 mL, 20 mmol) was added dropwise to a mixture of ethane-1,2-di­amine (0.34 ml, 5 mmol) and 4-bromo­phenol (1.73 g, 10 mmol) dissolved in dioxane (10 ml). The reaction mixture was stirred for 4 h at room temperature. Single crystals were obtained from this solution by slow evaporation of the solvent.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. All the H atoms were located in the difference electron-density map. C-bound H atoms were fixed geometrically (C—H = 0.95 or 0.99 Å) and refined using a riding-model approximation, with Uiso(H) set to 1.2Ueq of the parent atom.

Table 2
Experimental details

Crystal data
Chemical formula C18H18Br2N2O2
Mr 454.16
Crystal system, space group Monoclinic, C2/c
Temperature (K) 173
a, b, c (Å) 19.464 (2), 5.9444 (7), 17.2225 (19)
β (°) 121.557 (7)
V3) 1698.0 (3)
Z 4
Radiation type Mo Kα
μ (mm−1) 4.79
Crystal size (mm) 0.27 × 0.26 × 0.26
 
Data collection
Diffractometer STOE IPDS II two-circle
Absorption correction Multi-scan (X-AREA; Stoe & Cie, 2001[Stoe & Cie (2001). X-AREA and X-RED32. Stoe & Cie, Darmstadt, Germany.])
Tmin, Tmax 0.905, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 3703, 1583, 1391
Rint 0.078
(sin θ/λ)max−1) 0.607
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.143, 1.07
No. of reflections 1583
No. of parameters 110
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 1.40, −1.92
Computer programs: X-AREA (Stoe & Cie, 2001[Stoe & Cie (2001). X-AREA and X-RED32. Stoe & Cie, Darmstadt, Germany.]), SHELXS (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2014/7 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]) and XP in SHELXTL-Plus (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]).

Supporting information


Computing details top

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA (Stoe & Cie, 2001); data reduction: X-AREA (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL-2014/7 (Sheldrick, 2015); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL-2014/7 (Sheldrick, 2015).

1,2-Bis(6-bromo-3,4-dihydro-2H-benz[e][1,3]oxazin-3-yl)ethane top
Crystal data top
C18H18Br2N2O2F(000) = 904
Mr = 454.16Dx = 1.777 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
a = 19.464 (2) ÅCell parameters from 3703 reflections
b = 5.9444 (7) Åθ = 3.6–26.0°
c = 17.2225 (19) ŵ = 4.79 mm1
β = 121.557 (7)°T = 173 K
V = 1698.0 (3) Å3Block, colourless
Z = 40.27 × 0.26 × 0.26 mm
Data collection top
STOE IPDS II two-circle
diffractometer
1391 reflections with I > 2σ(I)
Radiation source: Genix 3D IµS microfocus X-ray sourceRint = 0.078
ω scansθmax = 25.6°, θmin = 3.6°
Absorption correction: multi-scan
(X-Area; Stoe & Cie, 2001)
h = 2023
Tmin = 0.905, Tmax = 1.000k = 77
3703 measured reflectionsl = 2020
1583 independent reflections
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.056 w = 1/[σ2(Fo2) + (0.099P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.143(Δ/σ)max < 0.001
S = 1.07Δρmax = 1.40 e Å3
1583 reflectionsΔρmin = 1.92 e Å3
110 parametersExtinction correction: SHELXL-2014/7 (Sheldrick 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0037 (8)
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br10.60406 (3)0.02845 (9)0.93353 (3)0.0226 (3)
O10.67962 (18)0.6369 (6)0.7231 (2)0.0176 (7)
N10.6072 (2)0.4166 (7)0.5842 (2)0.0130 (8)
C10.5323 (2)0.5473 (7)0.5467 (3)0.0141 (10)
H1A0.54300.70670.54010.017*
H1B0.51240.54060.58910.017*
C20.6783 (3)0.5494 (8)0.6434 (3)0.0155 (10)
H2A0.68110.67700.60820.019*
H2B0.72680.45520.66390.019*
C30.6620 (3)0.4788 (8)0.7681 (3)0.0141 (9)
C40.6259 (2)0.2721 (8)0.7288 (3)0.0142 (9)
C50.6091 (2)0.2158 (8)0.6343 (3)0.0140 (9)
H5A0.65130.11230.64000.017*
H5B0.55660.13720.59950.017*
C60.6083 (2)0.1218 (8)0.7781 (3)0.0147 (9)
H60.58410.01930.75260.018*
C70.6265 (3)0.1804 (8)0.8655 (3)0.0164 (9)
C80.6619 (3)0.3870 (9)0.9044 (3)0.0223 (10)
H80.67410.42480.96390.027*
C90.6787 (3)0.5348 (8)0.8552 (3)0.0192 (11)
H90.70210.67680.88070.023*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0261 (4)0.0229 (4)0.0255 (4)0.00128 (17)0.0181 (3)0.00527 (19)
O10.0161 (15)0.0160 (18)0.0166 (15)0.0043 (12)0.0058 (13)0.0018 (13)
N10.0078 (16)0.0135 (19)0.0148 (17)0.0005 (13)0.0039 (14)0.0003 (15)
C10.010 (2)0.013 (2)0.014 (2)0.0037 (16)0.0029 (19)0.0009 (18)
C20.012 (2)0.016 (2)0.019 (2)0.0051 (16)0.0081 (18)0.0034 (18)
C30.0114 (19)0.014 (2)0.014 (2)0.0000 (15)0.0047 (17)0.0021 (17)
C40.0093 (18)0.015 (2)0.014 (2)0.0023 (16)0.0030 (15)0.0016 (17)
C50.0105 (19)0.012 (2)0.016 (2)0.0009 (15)0.0039 (16)0.0021 (17)
C60.0098 (18)0.015 (2)0.018 (2)0.0015 (15)0.0062 (16)0.0022 (18)
C70.020 (2)0.014 (2)0.020 (2)0.0032 (16)0.0137 (18)0.0057 (18)
C80.028 (2)0.023 (3)0.017 (2)0.001 (2)0.0126 (19)0.0036 (19)
C90.023 (2)0.015 (2)0.019 (2)0.0003 (17)0.011 (2)0.0020 (18)
Geometric parameters (Å, º) top
Br1—C71.909 (5)C3—C41.402 (6)
O1—C31.372 (6)C4—C61.393 (7)
O1—C21.455 (6)C4—C51.519 (6)
N1—C21.450 (5)C5—H5A0.9900
N1—C51.462 (6)C5—H5B0.9900
N1—C11.470 (5)C6—C71.397 (7)
C1—C1i1.538 (8)C6—H60.9500
C1—H1A0.9900C7—C81.396 (7)
C1—H1B0.9900C8—C91.373 (8)
C2—H2A0.9900C8—H80.9500
C2—H2B0.9900C9—H90.9500
C3—C91.398 (7)
C3—O1—C2113.7 (4)C6—C4—C5121.9 (4)
C2—N1—C5108.0 (3)C3—C4—C5118.9 (4)
C2—N1—C1112.6 (4)N1—C5—C4112.2 (4)
C5—N1—C1113.8 (3)N1—C5—H5A109.2
N1—C1—C1i110.2 (4)C4—C5—H5A109.2
N1—C1—H1A109.6N1—C5—H5B109.2
C1i—C1—H1A109.6C4—C5—H5B109.2
N1—C1—H1B109.6H5A—C5—H5B107.9
C1i—C1—H1B109.6C4—C6—C7119.5 (4)
H1A—C1—H1B108.1C4—C6—H6120.3
N1—C2—O1113.4 (4)C7—C6—H6120.3
N1—C2—H2A108.9C8—C7—C6121.3 (4)
O1—C2—H2A108.9C8—C7—Br1119.4 (4)
N1—C2—H2B108.9C6—C7—Br1119.2 (4)
O1—C2—H2B108.9C9—C8—C7118.9 (4)
H2A—C2—H2B107.7C9—C8—H8120.5
O1—C3—C9117.2 (4)C7—C8—H8120.5
O1—C3—C4122.5 (4)C8—C9—C3120.8 (5)
C9—C3—C4120.3 (5)C8—C9—H9119.6
C6—C4—C3119.2 (4)C3—C9—H9119.6
C2—N1—C1—C1i151.1 (5)C1—N1—C5—C477.1 (4)
C5—N1—C1—C1i85.6 (6)C6—C4—C5—N1161.5 (4)
C5—N1—C2—O164.9 (5)C3—C4—C5—N120.1 (5)
C1—N1—C2—O161.6 (5)C3—C4—C6—C70.3 (6)
C3—O1—C2—N147.8 (5)C5—C4—C6—C7178.7 (4)
C2—O1—C3—C9166.5 (4)C4—C6—C7—C80.1 (7)
C2—O1—C3—C415.8 (5)C4—C6—C7—Br1178.8 (3)
O1—C3—C4—C6178.7 (4)C6—C7—C8—C90.2 (7)
C9—C3—C4—C61.1 (6)Br1—C7—C8—C9179.2 (4)
O1—C3—C4—C52.9 (6)C7—C8—C9—C31.0 (7)
C9—C3—C4—C5179.5 (4)O1—C3—C9—C8179.2 (4)
C2—N1—C5—C448.7 (5)C4—C3—C9—C81.4 (7)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C5—H5B···Br1ii0.993.043.951 (5)154
C2—H2B···O1iii0.992.643.506 (6)146
Symmetry codes: (ii) x+1, y, z+3/2; (iii) x+3/2, y1/2, z+3/2.
 

Acknowledgements

We acknowledge the Dirección de Investigaciones, Sede Bogotá (DIB) de la Universidad Nacional de Colombia for financial support of this work (research project No. 28427). JJR is also grateful to COLCIENCIAS for his doctoral scholarship

References

First citationChirachanchai, S., Phongtamrug, S. & Tashiro, K. (2011). Supramolecular Chemistry of Benzoxazines: From Simple, Selective, Effective, and Efficient Macrocyclization Pathways to Host-Guest Properties. In Handbook of Benzoxazine Resins, pp 331–352. Amsterdam: Elsevier.  Google Scholar
First citationLi, S., Huang, W., Liu, X., Yu, X. & Xiao, W. (2010). Polym. Adv. Technol. 21, 229–234.  CrossRef CAS Google Scholar
First citationPilato, L. (2010). Resin Chemistry In Phenolic Resins: A Century of Progress, edited by L. Pilato, pp. 41–91. Berlin Heidelberg: Springer-Verlag.  Google Scholar
First citationRivera, A., Camacho, J., Ríos-Motta, J., Fejfarová, K. & Dušek, M. (2012a). Acta Cryst. E68, o148.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationRivera, A., Camacho, J., Ríos-Motta, J., Kučeraková, M. & Dušek, M. (2012b). Acta Cryst. E68, o2734.  CSD CrossRef IUCr Journals Google Scholar
First citationRivera, A., Camacho, J., Ríos-Motta, J., Pojarová, M. & Dušek, M. (2011). Acta Cryst. E67, o2028.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationRivera, A., Rojas, J. J., Ríos-Motta, J., Dušek, M. & Fejfarová, K. (2010). Acta Cryst. E66, o1134.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationStoe & Cie (2001). X-AREA and X-RED32. Stoe & Cie, Darmstadt, Germany.  Google Scholar

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