Crystal structure of benzo[h]quinoline-3-carbox­amide

Grathwol, C.W.; Chrysochos, N.; Elvers, B.J.; Link, A.; Schulzke, C.

doi:10.1107/S2056989019014440

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ISSN: 2056-9890

Volume 75| Part 12| December 2019| Pages 1828-1832

https://doi.org/10.1107/S2056989019014440

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Crystal structure of benzo[h]quinoline-3-carboxamide

Christoph W. Grathwol,^a Nicolas Chrysochos,^b Benedict J. Elvers,^b Andreas Link ^a ^* and Carola Schulzke ^b ^*

^aInstitut für Pharmazie, Universität Greifswald, Friedrich-Ludwig-Jahn-Strasse 17, 17489 Greifswald, Germany, and ^bInstitut für Biochemie, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany
^*Correspondence e-mail: link@uni-greifswald.de, carola.schulzke@uni-greifswald.de

Edited by J. Simpson, University of Otago, New Zealand (Received 14 October 2019; accepted 22 October 2019; online 5 November 2019)

The title compound, C₁₄H₁₀N₂O, crystallizes in the monoclinic space group P2₁/c with four molecules in the unit cell. All 17 non-H atoms of one molecule lie essentially in one plane. In the unit cell, two pairs of molecules are exactly coplanar, while the angle between these two orientations is close to perfectly perpendicular at 87.64 (6)°. In the crystal, molecules adopt a 50:50 crisscross arrangement, which is held together by two nonclassical and two classical intermolecular hydrogen bonds. The hydrogen-bonding network together with off-centre π–π stacking interactions between the pyridine and outermost benzene rings, stack the molecules along the b-axis direction.

Keywords: crystal structure; benzoquinoline; nicotinamide derivative; photocyclization.

CCDC references: 1960760; 1960760

1. Chemical context

Quinoline and benzoquinoline scaffolds are common structural motifs in artificial, as well as natural products, and many of these compounds are of enormous value for pharmacotherapy. Their multifaceted biological efficacy is outstanding and ranges from cardiovascular (Ferlin et al., 2002 ; Abouzid et al., 2008 ) and anti-inflammatory effects (Kumar et al., 2009 ; Hussaini, 2016 ) to antimicrobial (El Shehry et al., 2018 ), as well as anticancer activity (Abdelsalam et al., 2019 ; Haiba et al., 2019 ; Jafari et al., 2019 ; Musiol, 2017 ; Marzaro et al., 2016 ). In a report on 3-(tetrazol-5-yl)quinolines with antiallergic potential, benzo[h]quinoline-3-carboxamide was mentioned as a synthetic intermediate, though its biological activity was not determined in that work (Erickson et al., 1979 ). In our recent studies on photoswitchable sirtuin inhibitors, we obtained benzo[h]quinoline-3-carboxamide as a side product of azastilbene photoisomerization (Grathwol et al., 2019 ). By UV radiation, (E)-5-styrylnicotinamide was transformed to its Z isomer as envisioned, but underwent photocyclization and successive oxidation, yielding two isomeric benzoquinoline derivatives; the identity of one of these was determined to be the benzo[h]quinoline derivative and its crystal structure is reported here.

2. Structural commentary

The title compound, benzo[h]quinoline-3-carboxamide, crystallizes in the monoclinic space group P2₁/c. Four molecules are present in the unit cell (Z = 4) and there is one molecule in the asymmetric unit. Benzo[h]quinoline-3-carboxamide consists of a nicotinamide unit being fused with a benzo[h]quinoline moiety, while the pyridine ring is shared between these two common structural building blocks (Fig. 1). The molecule is essentially flat, with a largest deviation from the plane through all 17 non-H atoms of 0.050 (2) Å (O1) and an r.m.s. deviation of 0.020 (2) Å. In the unit cell, the four molecules are arranged in two perfectly coplanar pairs, with a nearly perpendicular angle between the respective planes of the two pairs of 87.64 (6)° (Fig. 2). A plethora of crystal structures are known for compounds with one or other of the two building blocks that make up this molecule [for the nicotinamide scaffold, ConQuest finds over 2000 hits in the Cambridge Structural Database (CSD), while for benzoquinoline, there are over 500; Groom et al., 2016 ]. However, the specific combination in the title compound is unprecedented. Comparing the title compound to the known structures of unsubstituted nicotinamides, its pronounced planarity is most notable. In the six published structures in the space groups P2₁/c or P2₁/a, the angles between the aromatic plane (here C2/C3/N2/C4/C13/C14) and the amide substituent (here O1/N1/C1) range from 22.1 to 23.3° (general CSD refcode NICOAM; Wright & King, 1954 ; Miwa et al., 1999 ; Fábián et al., 2011 ; Jarzembska et al., 2014 ), i.e. this angle is quite consistent. In the only distinct polymorph of a nicotinamide in the space group P2/a, four distinct molecules were refined with this angle ranging from 8.1 to 22.4° (Li et al., 2011 ), i.e. they are not very consistent but still considerably larger than the corresponding angle found in the title compound, which is a mere 3.3 (4)°. This points toward an extension of the aromatic resonance systems to include the amide substituent. In the parent nicotinamide scaffolds, this does not occur. Similarly, the comparatively long C1=O1 distance of 1.238 (3) Å (average 1.23 Å) and the comparatively short C1—C2 distance of 1.491 (3) Å (average 1.50 Å in other nicotinamide structures) indicate some involvement of these atoms in resonance effects. In support of this extended resonance, in the nicotinamide structures, the aromatic C—C bonds are much less diverse (range 1.38–1.39 Å, indicating very strong aromaticity in the pyridine ring) than in the structure reported here. In fact, the C—C [range 1.376 (3)–1.414 (3) Å] and C—N [1.321 (3) and 1.360 (3) Å] bond lengths here are much more similar to the two known structures of 2-unsubstituted and 3-substituted benzo[h]quinolines (refcodes JAFVEU and SUDVES), with ranges of average C—C and C—N bond lengths of 1.38–1.42 and 1.32–1.36 Å, respectively (Martínez et al., 1992 ; Luo et al., 2015 ). The benzo[h]quinoline structural motif therefore dominates the observed metrical parameters of the molecule reported here, representing a fusion between a nicotinamide and a benzo[h]quinoline, with a partial extension of the aromaticity beyond the ring system and extending towards the amide substituent.

Figure 1
The molecular structure of benzo[h]quinoline-3-carboxamide. Displacement ellipsoids are shown at the 50% probability level.

Figure 2
The unit cell of benzo[h]quinoline-3-carboxamide in P2₁/c, with its four molecules in a coplanar and perpendicular arrangement, viewed along the ac diagonal.

3. Supramolecular features

In the crystal, the planar molecules are all arranged in planes in two distinct orientations, which are nearly perpendicular to each other [angle 87.64 (6)°]. This forms a crisscross pattern when viewed along the ac diagonal (Fig. 2). Classical inversion-related N1—H1P⋯O1 hydrogen bonds form dimers and generate R₂²(8) ring motifs (Fig. 3). Each molecule forms two classical (N—H⋯O and N—H⋯N) and two nonclassical (C—H⋯N and C—H⋯O) hydrogen bonds (Table 1), and these contacts link adjacent dimers into zigzag chains along the c-axis direction (Fig. 4). The observed packing is further stabilized by off-centre π–π stacking between the pyridine and outermost benzene rings of each of the coplanar layers [centroid-to-centroid distance = 3.610 (1) Å] (Fig. 5). These contacts combine to stack the molecules along the b-axis direction (Fig. 6).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N⋯N2ⁱ	0.97 (3)	2.17 (3)	3.133 (3)	173 (2)
N1—H1P⋯O1ⁱⁱ	0.93 (3)	1.96 (3)	2.895 (3)	175 (3)
C3—H3⋯N2ⁱ	0.95	2.41	3.361 (3)	174
C7—H7⋯O1ⁱⁱⁱ	0.95	2.45	3.140 (3)	129
Symmetry codes: (i) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) -x+1, -y-1, -z+1; (iii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Figure 3
Dimers formed by N—H⋯O hydrogen bonds.

Figure 4
Chains of dimers along the c-axis.

Figure 5
π–π stacking interactions, with centroids shown as coloured spheres. Cg1 and Cg2 are the centroids of the C5–C10 and C2/C3/N2/C4/C13/C14 rings, respectively.

Figure 6
The overall packing of the title compound, viewed along the b-axis direction.

4. Synthesis and crystallization

A solution of (E)-5-styrylnicotinamide (673 mg, 3.00 mmol, 1.00 equiv.) in methanol (350 ml) was treated with a solution of iodine (38 mg, 0.15 mmol, 0.05 equiv.) in methanol (50 ml). A slow stream of compressed air was bubbled through the reaction mixture while it was irradiated with UV light (six Vilber-Lourmat T8-C lamps, 8 W, 254 nm). After complete consumption of the starting material (24 h), the solvent was removed under reduced pressure. Purification of the residue by silica-gel column chromatography (n-hexane/THF, 1:1 v/v) gave pure benzo[h]quinoline-3-carboxamide as a colourless solid (yield 80 mg, 0.36 mmol, 12%). Crystallization was accomplished by slow evaporation of a solution in THF (5 mg ml⁻¹) and yielded the title compound as colourless needles: R_F = 0.32 (n-hexane/THF, 1:1 v/v); m.p. 549.8 K (decomposition); ¹H NMR, H,H-COSY (400 MHz, DMSO-d₆): δ (ppm) 9.48 (d, J = 2.2 Hz, 1H, C3-H), 9.26–9.19 (m, 1H, C6-H), 8.89 (d, J = 2.1 Hz, 1H, C14-H), 8.36 (s, br, 1H, N1-H), 8.12–8.07 (m, 1H, C9-H), 8.03 (d, J = 8.9 Hz, 1H, C11-H), 7.95 (d, J = 8.9 Hz, 1H, C12-H), 7.85–7.78 (m, 2H, C7-H, C8-H), 7.74 (s, br, 1H, N1-H); ¹³C NMR, DEPT135, HSQC, HMBC (101 MHz, DMSO-d₆): δ (ppm) 166.4 (C1), 147.8 (C3), 146.7 (C4), 135.5 (C14), 133.8 (C13), 130.3 (C5), 129.0 (C8), 128.1 (C9/C11), 128.0 (C9/C11), 127.8 (C2), 127.3 (C7), 125.8 (C12), 124.9 (C10), 124.1 (C6); IR (ATR): ν (cm⁻¹) 3336, 3136, 1686, 1482, 1395, 1295, 801, 691, 539, 489; ESI–HRMS calculated for [C₁₄H₁₀N₂O + H]⁺ 222.0793, found 222.0796; compound purity (220 nm): 100%.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. All C-bound H atoms constitute aromatic protons, which were attached in calculated positions and treated as riding with U_iso(H) = 1.2U_eq(C). The two amine H atoms were found and refined without any constraints or restraints.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₄H₁₀N₂O
M_r	222.24
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	170
a, b, c (Å)	12.634 (3), 4.9426 (10), 16.778 (3)
β (°)	100.53 (3)
V (Å³)	1030.0 (4)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.09
Crystal size (mm)	0.37 × 0.07 × 0.04

Data collection
Diffractometer	Stoe IPDS-2T
Absorption correction	Numerical face indexed
T_min, T_max	0.727, 0.997
No. of measured, independent and observed [I > 2σ(I)] reflections	10053, 2551, 1320
R_int	0.087
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.055, 0.167, 0.98
No. of reflections	2551
No. of parameters	163
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.23, −0.27
Computer programs: X-AREA (Stoe & Cie, 2010 ), SHELXT2018 (Sheldrick, 2015a ), SHELXL2018 (Sheldrick, 2015b ), XP in SHELXTL (Sheldrick, 2008 ), Mercury (Macrae et al., 2008 ), CIFTAB (Sheldrick, 2015b) and publCIF (Westrip, 2010 ).

Supporting information

CCDC references: 1960760; 1960760

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989019014440/sj5580sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019014440/sj5580Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989019014440/sj5580Isup3.cml

checkCIF report

Computing details top

Data collection: X-AREA (Stoe & Cie, 2010).; cell refinement: X-AREA (Stoe & Cie, 2010).; data reduction: X-AREA (Stoe & Cie, 2010).; program(s) used to solve structure: SHELXT2018 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2008); software used to prepare material for publication: CIFTAB (Sheldrick, 2015b) and publCIF (Westrip, 2010).

Benzo[h]quinoline-3-carboxamide top

Crystal data top

C₁₄H₁₀N₂O	F(000) = 464
M_r = 222.24	D_x = 1.433 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.634 (3) Å	Cell parameters from 11960 reflections
b = 4.9426 (10) Å	θ = 6.4–59.0°
c = 16.778 (3) Å	µ = 0.09 mm⁻¹
β = 100.53 (3)°	T = 170 K
V = 1030.0 (4) Å³	Needle, colourless
Z = 4	0.37 × 0.07 × 0.04 mm

Data collection top

Stoe IPDS2T diffractometer	2551 independent reflections
Radiation source: fine-focus sealed tube	1320 reflections with I > 2σ(I)
Detector resolution: 6.67 pixels mm^-1	R_int = 0.087
ω scans	θ_max = 28.3°, θ_min = 3.2°
Absorption correction: numerical face indexed	h = −16→16
T_min = 0.727, T_max = 0.997	k = −6→6
10053 measured reflections	l = −22→22

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.055	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.167	w = 1/[σ²(F_o²) + (0.086P)²] where P = (F_o² + 2F_c²)/3
S = 0.98	(Δ/σ)_max < 0.001
2551 reflections	Δρ_max = 0.23 e Å⁻³
163 parameters	Δρ_min = −0.27 e Å⁻³
0 restraints	Extinction correction: SHELXL2018 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: dual	Extinction coefficient: 0.019 (4)

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

	x	y	z	U_iso*/U_eq
O1	0.60103 (14)	−0.2438 (3)	0.51392 (9)	0.0364 (4)
N2	0.63400 (15)	0.2758 (4)	0.28016 (11)	0.0304 (5)
N1	0.48278 (17)	−0.3250 (4)	0.39872 (12)	0.0331 (5)
C1	0.56558 (19)	−0.1907 (4)	0.44191 (13)	0.0312 (5)
C2	0.61839 (18)	0.0252 (4)	0.40098 (12)	0.0287 (5)
C3	0.58725 (19)	0.0909 (4)	0.31880 (13)	0.0311 (5)
H3	0.528010	−0.004871	0.288573	0.037*
C4	0.71867 (17)	0.4149 (4)	0.32278 (12)	0.0274 (5)
C5	0.77008 (18)	0.6182 (4)	0.28123 (13)	0.0292 (5)
C6	0.7362 (2)	0.6735 (5)	0.19826 (13)	0.0332 (5)
H6	0.678537	0.573337	0.167687	0.040*
C7	0.7858 (2)	0.8702 (5)	0.16151 (14)	0.0360 (6)
H7	0.762331	0.905703	0.105414	0.043*
C8	0.8707 (2)	1.0200 (5)	0.20521 (15)	0.0375 (6)
H8	0.904089	1.157365	0.178843	0.045*
C9	0.90571 (19)	0.9702 (5)	0.28530 (14)	0.0346 (6)
H9	0.963477	1.073076	0.314661	0.041*
C10	0.85689 (18)	0.7665 (4)	0.32529 (13)	0.0305 (5)
C11	0.8935 (2)	0.7074 (5)	0.40961 (14)	0.0350 (6)
H11	0.952662	0.805664	0.438992	0.042*
C12	0.84594 (19)	0.5161 (5)	0.44794 (13)	0.0329 (5)
H12	0.872211	0.481242	0.503736	0.039*
C13	0.75657 (17)	0.3646 (4)	0.40605 (12)	0.0291 (5)
C14	0.70365 (19)	0.1668 (4)	0.44428 (13)	0.0307 (5)
H14	0.726853	0.130640	0.500358	0.037*
H1N	0.449 (2)	−0.279 (6)	0.344 (2)	0.059 (9)*
H1P	0.452 (2)	−0.464 (6)	0.4246 (16)	0.054 (8)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0445 (10)	0.0389 (9)	0.0247 (8)	−0.0018 (8)	0.0036 (7)	0.0056 (7)
N2	0.0311 (11)	0.0302 (10)	0.0293 (9)	−0.0018 (8)	0.0037 (8)	0.0005 (8)
N1	0.0373 (12)	0.0331 (11)	0.0280 (10)	−0.0018 (9)	0.0036 (9)	0.0020 (8)
C1	0.0351 (13)	0.0302 (11)	0.0285 (11)	0.0031 (10)	0.0064 (10)	0.0001 (9)
C2	0.0310 (12)	0.0281 (11)	0.0275 (10)	0.0048 (9)	0.0068 (9)	0.0004 (9)
C3	0.0333 (12)	0.0306 (11)	0.0286 (11)	−0.0012 (10)	0.0033 (9)	0.0002 (9)
C4	0.0278 (11)	0.0261 (11)	0.0279 (11)	0.0029 (9)	0.0036 (9)	−0.0021 (9)
C5	0.0299 (12)	0.0276 (11)	0.0307 (11)	0.0034 (10)	0.0068 (9)	−0.0007 (9)
C6	0.0345 (13)	0.0355 (13)	0.0295 (11)	−0.0024 (10)	0.0058 (10)	0.0009 (9)
C7	0.0372 (14)	0.0387 (13)	0.0327 (11)	−0.0005 (11)	0.0082 (10)	0.0042 (10)
C8	0.0367 (13)	0.0348 (13)	0.0428 (13)	−0.0015 (11)	0.0124 (11)	0.0025 (11)
C9	0.0325 (13)	0.0324 (12)	0.0393 (13)	0.0003 (10)	0.0079 (10)	−0.0006 (10)
C10	0.0291 (12)	0.0280 (11)	0.0351 (11)	0.0030 (9)	0.0079 (9)	−0.0021 (9)
C11	0.0319 (13)	0.0379 (13)	0.0342 (12)	−0.0024 (10)	0.0037 (10)	−0.0063 (10)
C12	0.0324 (12)	0.0372 (12)	0.0274 (11)	0.0009 (10)	0.0009 (9)	−0.0027 (9)
C13	0.0303 (12)	0.0302 (11)	0.0260 (10)	0.0045 (10)	0.0033 (9)	0.0006 (9)
C14	0.0352 (13)	0.0312 (12)	0.0248 (10)	0.0053 (10)	0.0034 (9)	0.0009 (9)

Geometric parameters (Å, º) top

O1—C1	1.238 (3)	C6—H6	0.9500
N2—C3	1.321 (3)	C7—C8	1.396 (3)
N2—C4	1.360 (3)	C7—H7	0.9500
N1—C1	1.335 (3)	C8—C9	1.358 (3)
N1—H1N	0.97 (3)	C8—H8	0.9500
N1—H1P	0.93 (3)	C9—C10	1.413 (3)
C1—C2	1.491 (3)	C9—H9	0.9500
C2—C14	1.376 (3)	C10—C11	1.436 (3)
C2—C3	1.401 (3)	C11—C12	1.346 (3)
C3—H3	0.9500	C11—H11	0.9500
C4—C13	1.414 (3)	C12—C13	1.428 (3)
C4—C5	1.443 (3)	C12—H12	0.9500
C5—C6	1.406 (3)	C13—C14	1.404 (3)
C5—C10	1.411 (3)	C14—H14	0.9500
C6—C7	1.364 (3)

C3—N2—C4	118.11 (19)	C6—C7—H7	119.6
C1—N1—H1N	124.6 (17)	C8—C7—H7	119.6
C1—N1—H1P	117.5 (17)	C9—C8—C7	120.2 (2)
H1N—N1—H1P	118 (2)	C9—C8—H8	119.9
O1—C1—N1	122.2 (2)	C7—C8—H8	119.9
O1—C1—C2	119.3 (2)	C8—C9—C10	120.5 (2)
N1—C1—C2	118.55 (19)	C8—C9—H9	119.7
C14—C2—C3	117.0 (2)	C10—C9—H9	119.7
C14—C2—C1	119.62 (19)	C5—C10—C9	119.1 (2)
C3—C2—C1	123.4 (2)	C5—C10—C11	119.4 (2)
N2—C3—C2	125.0 (2)	C9—C10—C11	121.5 (2)
N2—C3—H3	117.5	C12—C11—C10	121.5 (2)
C2—C3—H3	117.5	C12—C11—H11	119.3
N2—C4—C13	121.5 (2)	C10—C11—H11	119.3
N2—C4—C5	118.57 (19)	C11—C12—C13	121.0 (2)
C13—C4—C5	119.92 (19)	C11—C12—H12	119.5
C6—C5—C10	119.0 (2)	C13—C12—H12	119.5
C6—C5—C4	122.1 (2)	C14—C13—C4	118.1 (2)
C10—C5—C4	118.95 (19)	C14—C13—C12	122.68 (19)
C7—C6—C5	120.3 (2)	C4—C13—C12	119.3 (2)
C7—C6—H6	119.9	C2—C14—C13	120.37 (19)
C5—C6—H6	119.9	C2—C14—H14	119.8
C6—C7—C8	120.9 (2)	C13—C14—H14	119.8

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···N2ⁱ	0.97 (3)	2.17 (3)	3.133 (3)	173 (2)
N1—H1P···O1ⁱⁱ	0.93 (3)	1.96 (3)	2.895 (3)	175 (3)
C3—H3···N2ⁱ	0.95	2.41	3.361 (3)	174
C7—H7···O1ⁱⁱⁱ	0.95	2.45	3.140 (3)	129

Symmetry codes: (i) −x+1, y−1/2, −z+1/2; (ii) −x+1, −y−1, −z+1; (iii) x, −y+1/2, z−1/2.

Acknowledgements

The authors acknowledge support for the Article Processing Charge from the DFG (German Research Foundation) and the Open Access Publication Fund of the University of Greifswald.

Funding information

Funding for this research was provided by: Deutsche Forschungsgemeinschaft (grant No. 393148499).

References

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