Crystal structure of 2,2′-(ethane-1,2-di­yl)bis­(2,3-di­hydro-1H-naphtho­[1,2-e][1,3]oxazine): a prospective raw material for polybenzoxazines

Rivera, A.; Cepeda-Santamaría, J.E.; Ríos-Motta, J.; Bolte, M.

doi:10.1107/S2056989017006673

research communications

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Volume 73| Part 6| June 2017| Pages 832-834

https://doi.org/10.1107/S2056989017006673

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Crystal structure of 2,2′-(ethane-1,2-diyl)bis(2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazine): a prospective raw material for polybenzoxazines

Augusto Rivera,^a ^* Juan E. Cepeda-Santamaría,^a Jaime Ríos-Motta ^a and Michael Bolte ^b

^aUniversidad Nacional de Colombia, Sede Bogotá, Facultad de Ciencias, Departamento de Química, Cra 30 No. 45-03, Bogotá, Código Postal 111321, Colombia, and ^bInstitut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von Laue-Strasse 7, 60438 Frankfurt/Main, Germany
^*Correspondence e-mail: ariverau@unal.edu.co

Edited by J. Simpson, University of Otago, New Zealand (Received 28 April 2017; accepted 3 May 2017; online 9 May 2017)

In the title compound, C₂₆H₂₄N₂O₂, the oxazine moiety is fused to a naphthalene ring system. The asymmetric unit consists of one half of the molecule, which lies about an inversion centre. The C atoms of the ethylene spacer group adopt an antiperiplanar arrangement. The oxazine ring adopts a half-chair conformation. In the crystal, supramolecular chains running along the b axis are formed via short C—H⋯π contacts. The crystal studied was a non-merohedral twin with a fractional contribution of 0.168 (2) of the minor twin component.

Keywords: crystal structure; short contacts; benzoxazines; phenolic resins.

CCDC reference: 1547729

1. Chemical context

The oxazine moiety is well known as a building block for high-performance phenolic resins, which are of great interest in industry due to their superior mechanical and physical properties together with unusually high thermal resistance (Kiskan & Yagci, 2005 ). Recently, because of their high flexibility in molecular design and performance-to-cost ratio, these monomers have gained attention for the preparation of cured thermosetting resins (Song et al., 2014 ; Yeganeh & Jangi, 2010 ). Benzoxazines and naphthoxazines, originally proposed by Holly & Cope (1944 ) and subsequently elaborated by Burke and co-workers (Burke et al., 1952 ), are obtained by Mannich-type condensation–cyclization reactions of phenols or naphthols with formaldehyde and primary amines in a 1:2:1 ratio (Deck et al., 2014 ). Interest in the synthesis of polybenzoxazines and polynaphthoxazines has greatly increased during the past few years as they have a great deal of molecular design flexibility compared to ordinary phenolics (Yildirim et al., 2006 ). The title bisnapthoxazine, 2,2′-(ethane-1,2-diyl)bis(2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazine), C₂₆H₂₄N₂O₂, was prepared by condensation of 2-naphthol with ethylenediamine and formaldehyde in a 2:1:4 molar ratio at room temperature for 15 min in methanol solution. Evaporation at room temperature afforded the title compound in 73% yield after recrystallization.

2. Structural commentary

In general terms, the structure of the title compound (Fig. 1) is similar to those of other naphthoxazine derivatives that have been reported in that the oxazine moiety adopts a half-chair conformation (Yang et al., 2007 ; Rivera et al., 2015 ), with puckering parameters Q = 0.478 (3) Å, θ = 51.5 (4)°, φ = 86.6 (4)°, and the ethylene spacer group adopts an antiperiplanar arrangement as observed in 3,3′-(ethane-1,2-diyl)bis(3,4-dihydro-2H-1,3-benzoxazine) (Rivera et al., 2012 ), with a N1—C13—C13ⁱ—N1ⁱ torsion angle of 180.0° [symmetry code: (i) 1 − x, 1 − y, 1 − z]. However, unlike the related structures, which crystallized in monoclinic space groups with one molecule in the asymmetric unit (Yang et al., 2007; Rivera et al., 2012, 2015), the title compound (I) crystallizes with just half a molecule in the asymmetric unit in the space group P2₁/c, utilizing the crystallographic inversion centre in the molecular symmetry. The other half of the molecule is generated by the symmetry operation (1 − x, 1 − y, 1 − z).

Figure 1
The molecular structure of the title compound, with displacement ellipsoids 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 aromatic C—C bonds of naphthalene ring system have a narrow range of distances [from 1.365 (5) to 1.431 (4) Å]. The central C5—C10 bond at 1.415 (4) Å is, however, shorter by 0.014 Å than those in related structures (Yang et al., 2007; Rivera et al., 2015). The N1—C1 and O1—C1 bond lengths are normal and comparable to the corresponding values observed in these related structures.

3. Supramolecular features

In the crystal, the packing of the title compound is dominated by short contacts (Table 1), as indicated by a PLATON (Spek, 2009 ) analysis. These contacts result from short C12—H12B⋯C2 and C12—H12B⋯C3 separations, which at 2.75 Å are both 0.15 Å shorter than the sum of the van der Waals radii, while the C—H⋯Cg1 contact to the mid-point of the C2–-C3 bond is even shorter at approximately 2.65 Å. These contacts are also much shorter than the C—H⋯Cg2 contact to the centroid of the C2–C4/C11/C12 ring (Fig. 2). The molecules are by these short C—H⋯π contacts linked into chains propagating along the b-axis direction (Fig. 3).

Table 1
Selected short-contact geometry (Å, °)

Cg1 is the mid-point of the C2—C3 bond and Cg2 is the centroid of the C2–C4/C11/C12 ring.

C—H⋯C	H⋯C	C—H⋯C
C12—H12B⋯C2ⁱ	2.75	169
C12—H12B⋯C3ⁱ	2.75	142
C12–H12B⋯Cg1	2.654	157
C12–H12B⋯Cg2	3.073	155
Symmetry code: (i) x, −1 + y, z.

Figure 2
Possible C—H⋯π contacts, shown as dotted green lines, between molecules of (I)

. Bond mid-points and ring centroids are shown as colored spheres.

Figure 3
Crystal packing of (I)

, showing C—H⋯(C,C) short contacts that result in chains propagating along the b-axis direction.

4. Database survey

The title compound is the first example of two naphtho-oxazine moieties linked by an ethylene bridge.

5. Synthesis and crystallization

The title compound was prepared as described by Rivera et al. (2006 ). Crystals were obtained by slow evaporation of the reaction solution at ambient temperature and were isolated from the solution before complete evaporation of the solvent mixture.

6. Refinement details

Crystal data, data collection and structure refinement details are summarized in Table 2. All 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 U_iso(H) set to 1.2U_eq of the parent atom. The crystal was a non-merohedral twin with a fractional contribution of 0.168 (2) of the minor twin component.

Table 2
Experimental details

Crystal data
Chemical formula	C₂₆H₂₄N₂O₂
M_r	396.47
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	173
a, b, c (Å)	9.8658 (10), 5.0979 (4), 19.551 (2)
β (°)	96.033 (8)
V (Å³)	977.87 (16)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	0.09
Crystal size (mm)	0.27 × 0.11 × 0.04

Data collection
Diffractometer	Stoe IPDS II two-circle
Absorption correction	Multi-scan (X-AREA; Stoe & Cie, 2001 )
T_min, T_max	0.443, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	9335, 9335, 5706
(sin θ/λ)_max (Å⁻¹)	0.625

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.063, 0.130, 0.94
No. of reflections	9335
No. of parameters	137
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.53, −0.34
Computer programs: X-AREA (Stoe & Cie, 2001), SHELXT (Sheldrick, 2015a ), XP in SHELXTL-Plus (Sheldrick, 2008 ), SHELXL2016 (Sheldrick, 2015b ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1547729

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989017006673/sj5529sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017006673/sj5529Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989017006673/sj5529Isup3.cml

checkCIF report

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: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL2016 (Sheldrick, 2015b) and publCIF (Westrip, 2010).

2,2'-(Ethane-1,2-diyl)bis(2,3-dihydro-1H-naphtho[1,2-e][1,3]oxazine) top

Crystal data top

C₂₆H₂₄N₂O₂	F(000) = 420
M_r = 396.47	D_x = 1.347 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.8658 (10) Å	Cell parameters from 9056 reflections
b = 5.0979 (4) Å	θ = 2.8–26.4°
c = 19.551 (2) Å	µ = 0.09 mm⁻¹
β = 96.033 (8)°	T = 173 K
V = 977.87 (16) Å³	Needle, colourless
Z = 2	0.27 × 0.11 × 0.04 mm

Data collection top

Stoe IPDS II two-circle diffractometer	9335 independent reflections
Radiation source: Genix 3D IµS microfocus X-ray source	5706 reflections with I > 2σ(I)
ω scans	θ_max = 26.4°, θ_min = 2.8°
Absorption correction: multi-scan (X-AREA; Stoe & Cie, 2001)	h = −12→12
T_min = 0.443, T_max = 1.000	k = −6→6
9335 measured reflections	l = −24→24

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.063	H-atom parameters constrained
wR(F²) = 0.130	w = 1/[σ²(F_o²) + (0.050P)²] where P = (F_o² + 2F_c²)/3
S = 0.94	(Δ/σ)_max < 0.001
9335 reflections	Δρ_max = 0.53 e Å⁻³
137 parameters	Δρ_min = −0.34 e Å⁻³

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.

Refinement. Refined as a 2-component twin

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
N1	0.3328 (2)	0.3467 (5)	0.51587 (12)	0.0291 (6)
O1	0.14340 (19)	0.6404 (5)	0.52587 (10)	0.0346 (5)
C1	0.1935 (3)	0.4104 (7)	0.49256 (16)	0.0351 (8)
H1A	0.135064	0.258586	0.501152	0.042*
H1B	0.185528	0.440900	0.442290	0.042*
C2	0.1675 (3)	0.6281 (6)	0.59661 (15)	0.0302 (7)
C3	0.0926 (3)	0.8089 (6)	0.63272 (17)	0.0350 (8)
H3	0.029986	0.925542	0.608217	0.042*
C4	0.1107 (3)	0.8150 (7)	0.70288 (17)	0.0370 (8)
H4	0.061911	0.939265	0.726968	0.044*
C5	0.2015 (3)	0.6382 (7)	0.74028 (15)	0.0319 (7)
C6	0.2182 (3)	0.6366 (7)	0.81341 (16)	0.0397 (8)
H6	0.169242	0.759116	0.837964	0.048*
C7	0.3039 (3)	0.4611 (7)	0.84895 (16)	0.0419 (9)
H7	0.313599	0.460117	0.897805	0.050*
C8	0.3771 (3)	0.2834 (7)	0.81263 (17)	0.0421 (9)
H8	0.436829	0.162438	0.837424	0.051*
C9	0.3648 (3)	0.2792 (7)	0.74225 (15)	0.0355 (8)
H9	0.415732	0.155997	0.718946	0.043*
C10	0.2761 (3)	0.4585 (6)	0.70373 (15)	0.0295 (7)
C11	0.2593 (3)	0.4567 (6)	0.63016 (15)	0.0276 (7)
C12	0.3413 (3)	0.2746 (6)	0.58900 (14)	0.0288 (7)
H12A	0.437938	0.278593	0.608671	0.035*
H12B	0.307562	0.092959	0.593092	0.035*
C13	0.4289 (2)	0.5552 (6)	0.50126 (15)	0.0290 (7)
H13A	0.430945	0.691415	0.537435	0.035*
H13B	0.397638	0.638414	0.456628	0.035*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0234 (11)	0.0348 (16)	0.0294 (13)	−0.0034 (11)	0.0031 (9)	0.0008 (11)
O1	0.0264 (10)	0.0434 (14)	0.0335 (12)	0.0053 (9)	0.0002 (8)	0.0001 (10)
C1	0.0240 (14)	0.047 (2)	0.0339 (16)	−0.0011 (13)	0.0013 (12)	−0.0078 (15)
C2	0.0194 (13)	0.0348 (18)	0.0365 (17)	−0.0036 (13)	0.0034 (12)	−0.0013 (14)
C3	0.0233 (13)	0.035 (2)	0.047 (2)	0.0023 (13)	0.0047 (13)	−0.0013 (15)
C4	0.0284 (14)	0.033 (2)	0.051 (2)	−0.0017 (13)	0.0120 (14)	−0.0119 (15)
C5	0.0270 (14)	0.0336 (18)	0.0358 (18)	−0.0090 (13)	0.0070 (12)	−0.0041 (14)
C6	0.0412 (17)	0.040 (2)	0.0398 (19)	−0.0157 (16)	0.0151 (14)	−0.0116 (16)
C7	0.0501 (19)	0.048 (2)	0.0286 (17)	−0.0210 (17)	0.0061 (14)	0.0037 (15)
C8	0.0444 (17)	0.043 (2)	0.038 (2)	−0.0089 (16)	−0.0002 (15)	0.0075 (16)
C9	0.0355 (15)	0.034 (2)	0.0377 (19)	−0.0048 (14)	0.0057 (13)	0.0047 (15)
C10	0.0244 (13)	0.0273 (17)	0.0374 (17)	−0.0071 (12)	0.0067 (12)	−0.0008 (13)
C11	0.0232 (12)	0.0280 (17)	0.0322 (16)	−0.0049 (12)	0.0058 (11)	−0.0010 (13)
C12	0.0266 (13)	0.0287 (17)	0.0319 (16)	0.0005 (12)	0.0067 (12)	0.0002 (13)
C13	0.0250 (13)	0.0322 (18)	0.0302 (15)	0.0019 (12)	0.0047 (12)	0.0014 (14)

Geometric parameters (Å, º) top

N1—C1	1.439 (3)	C6—C7	1.369 (5)
N1—C13	1.472 (4)	C6—H6	0.9500
N1—C12	1.470 (4)	C7—C8	1.398 (5)
O1—C2	1.380 (4)	C7—H7	0.9500
O1—C1	1.453 (4)	C8—C9	1.369 (4)
C1—H1A	0.9900	C8—H8	0.9500
C1—H1B	0.9900	C9—C10	1.425 (4)
C2—C11	1.375 (4)	C9—H9	0.9500
C2—C3	1.415 (4)	C10—C11	1.431 (4)
C3—C4	1.365 (5)	C11—C12	1.517 (4)
C3—H3	0.9500	C12—H12A	0.9900
C4—C5	1.418 (4)	C12—H12B	0.9900
C4—H4	0.9500	C13—C13ⁱ	1.518 (5)
C5—C10	1.415 (4)	C13—H13A	0.9900
C5—C6	1.422 (4)	C13—H13B	0.9900

C1—N1—C13	112.9 (2)	C6—C7—H7	120.3
C1—N1—C12	108.6 (2)	C8—C7—H7	120.3
C13—N1—C12	113.4 (2)	C9—C8—C7	121.7 (3)
C2—O1—C1	112.5 (2)	C9—C8—H8	119.2
N1—C1—O1	113.5 (2)	C7—C8—H8	119.2
N1—C1—H1A	108.9	C8—C9—C10	120.4 (3)
O1—C1—H1A	108.9	C8—C9—H9	119.8
N1—C1—H1B	108.9	C10—C9—H9	119.8
O1—C1—H1B	108.9	C5—C10—C9	118.1 (3)
H1A—C1—H1B	107.7	C5—C10—C11	120.0 (3)
C11—C2—O1	122.9 (3)	C9—C10—C11	121.8 (3)
C11—C2—C3	121.9 (3)	C2—C11—C10	118.5 (3)
O1—C2—C3	115.2 (3)	C2—C11—C12	119.8 (3)
C4—C3—C2	119.7 (3)	C10—C11—C12	121.7 (3)
C4—C3—H3	120.1	N1—C12—C11	112.6 (2)
C2—C3—H3	120.1	N1—C12—H12A	109.1
C3—C4—C5	120.8 (3)	C11—C12—H12A	109.1
C3—C4—H4	119.6	N1—C12—H12B	109.1
C5—C4—H4	119.6	C11—C12—H12B	109.1
C10—C5—C4	119.0 (3)	H12A—C12—H12B	107.8
C10—C5—C6	119.5 (3)	N1—C13—C13ⁱ	110.8 (3)
C4—C5—C6	121.5 (3)	N1—C13—H13A	109.5
C7—C6—C5	120.9 (3)	C13ⁱ—C13—H13A	109.5
C7—C6—H6	119.5	N1—C13—H13B	109.5
C5—C6—H6	119.5	C13ⁱ—C13—H13B	109.5
C6—C7—C8	119.4 (3)	H13A—C13—H13B	108.1

C13—N1—C1—O1	−62.2 (3)	C6—C5—C10—C11	179.5 (3)
C12—N1—C1—O1	64.5 (3)	C8—C9—C10—C5	−0.3 (4)
C2—O1—C1—N1	−50.6 (3)	C8—C9—C10—C11	−179.0 (3)
C1—O1—C2—C11	16.5 (4)	O1—C2—C11—C10	−179.6 (3)
C1—O1—C2—C3	−164.7 (2)	C3—C2—C11—C10	1.6 (4)
C11—C2—C3—C4	−0.2 (5)	O1—C2—C11—C12	1.3 (4)
O1—C2—C3—C4	−179.0 (3)	C3—C2—C11—C12	−177.5 (3)
C2—C3—C4—C5	−1.5 (5)	C5—C10—C11—C2	−1.4 (4)
C3—C4—C5—C10	1.6 (4)	C9—C10—C11—C2	177.2 (3)
C3—C4—C5—C6	−178.0 (3)	C5—C10—C11—C12	177.6 (3)
C10—C5—C6—C7	−1.0 (5)	C9—C10—C11—C12	−3.7 (4)
C4—C5—C6—C7	178.6 (3)	C1—N1—C12—C11	−43.2 (3)
C5—C6—C7—C8	0.8 (5)	C13—N1—C12—C11	83.2 (3)
C6—C7—C8—C9	−0.3 (5)	C2—C11—C12—N1	12.7 (4)
C7—C8—C9—C10	0.1 (5)	C10—C11—C12—N1	−166.3 (3)
C4—C5—C10—C9	−178.8 (3)	C1—N1—C13—C13ⁱ	−156.7 (3)
C6—C5—C10—C9	0.8 (4)	C12—N1—C13—C13ⁱ	79.2 (4)
C4—C5—C10—C11	−0.1 (4)

Symmetry code: (i) −x+1, −y+1, −z+1.

Selected short-contact geometry (Å, °) top

Cg1 is the mid-point of the C2—C3 bond and Cg2 is the centroid of the C2–C4/C11/C12 ring.

C—H···C	H···C	C—H···C
C12—H12B···C2ⁱ	2.75	169
C12—H12B···C3ⁱ	2.75	142
C12–H12B···Cg1	2.654	157
C12–H12B···Cg2	3.073	155

Symmetry code: (i) x, -1 + y, z.

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. 35816).

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