Structural studies of 3-chloro-N-(8′-quinolyl)×benzo[b] thiophene-2-carboxamide

Article abstract of DOI:10.1134/S0022476611030292

3-Chloro-N-(8′-quinolyl)benzo[b]thiophene-2-carboxamide was synthesized from 3-chlorobenzo[b] thiophene -2-carboxyl chloride and 8-aminoquinoline in the presence of triethylamine. The single crystal X-ray structure determination confirmed the earlier proposed structure and also characterized by ¹HNMR, and Mass spectroscopy. Crystallographic study reveals that the structure crystallizes in monoclinic system, a = 14.878(4) A, b = 8.4292(15) A, c = 25.461(7) A, β = 112.022(18)°, Z = 8, V = 2960.20(12) A³ with space group C2/c (No. 15). In the structure packing, three kinds of interactions are responsible for the stability of the structure. Infinite two-dimensional stair-like layered chains are formed by relatively strong intermolecular hydrogen bonds [C14-H14...O1]. These parallel chains are connected by several π-π and CH-π interactions, alternatively. There are two such parallel chains with 70.53°, which are in contact by van der Waals interactions. Copyright

Full text of DOI:10.1134/S0022476611030292

Journal of Structural Chemistry. Vol. 52, No. 3, pp. 639-643, 2011
Original Russian Text Copyright © 2011 by A. Abbasi, S. Zamanian, S. Tarighi, and A. Badiei
STRUCTURAL STUDIES OF 3-CHLORO-N-(8′-QUINOLYL)×
BENZO[b]THIOPHENE-2-CARBOXAMIDE
©
A. Abbasi, S. Zamanian, S. Tarighi, and A. Badiei
UDС 541.6:547.12
3-Chloro-N-(8′-quinolyl)benzo[b]thiophene-2-carboxamide was synthesized from 3-chlorobenzo[b]
thiophene -2-carboxyl chloride and 8-aminoquinoline in the presence of triethylamine. The single crystal
1
X-ray structure determination confirmed the earlier proposed structure and also characterized by HNMR,
and Mass spectroscopy. Crystallographic study reveals that the structure crystallizes in monoclinic system,
3
a = 14.878(4) Å, b = 8.4292(15) Å, c = 25.461(7) Å, β = 112.022(18)°, Z = 8, V = 2960.20(12) Å with
space group C2/c (No. 15). In the structure packing, three kinds of interactions are responsible for the
stability of the structure. Infinite two-dimensional stair-like layered chains are formed by relatively strong
intermolecular hydrogen bonds [C14–H14…O1]. These parallel chains are connected by several π–π and
CH–π interactions, alternatively. There are two such parallel chains with 70.53°, which are in contact by
van der Waals interactions.
Keywords: benzothiophene, carboxamide, crystal structure, hydrogen bonding, CH–π interaction, π–π
interaction.
Synthesis of polycyclic heterocyclic ring systems have been followed by many groups of researchers [1, 2]. One of
the best procedures in this field is photochemical reaction, in which a good leaving group will leave an aromatic ring under a
radically mechanism, producing a radical that can facilitate the formation of fused neighbor ring systems [1, 2]. Our interest
in these structures arises from easily converting to larger useful structures. Nowadays, many research groups reported this
type of structures. Among them, Carminski–Zamola and coworkers have reported such compounds with a carboxyl group as
substitution [3]. Following our previous work in the synthesis of 3-chlorobenzo[b]thiophene-2-carbonyl chloride (1) [4], we
were interested in preceding these reactions in order to get phenanthroline ring systems, which have widespread biological,
pesticidal and pharmacological activities [5-9]. 3-Chloro-N-(8′-quinolyl)benzo[b]thiophene-2-carboxamide (2), with a
chloride group is a suitable choice for photocyclization system that can serve as a basic substance for preparation of
[1]benzothieno[2,3-c][1,10]phenanthroline (3) (Scheme 1). Compound 2 was previously reported in one step in 1996 by
Halverson and Castle [10]. However their report was merely based on NMR and elemental analysis. In the current study, we
synthesized compound 2 with some modifications (i.e. using different solvent and crystallization technique, resulting in better
yield), in part to confirm its structure by getting suitable crystals for crystallography.
Experimental. The synthesis was performed starting from 3-chlorobenzo[b]thiophene-2-carboxyl chloride (1) that
was reported in our previous work [3]. A solution of 8-aminoquinoline (0.95 g, 6.56 mmol) in 150 ml of benzene was added
to (1) (1.52 g, 6.56 mmol). Triethylamine (6.8 mmol) was then added slowly, followed by four hours reflux. Insoluble
impurities were filtered out from the hot solution. Allowing to remains undisturbed and slow evaporation of the mother
School of Chemistry, College of Science, University of Tehran, Iran; aabbasi@khayam.ut.ac.ir. The text was
submitted by the authors in English. Zhurnal Strukturnoi Khimii, Vol. 52, No. 3, pp. 653-656, May-June, 2011. Original
article submitted August 30, 2009.
0022-4766/11/5203-0639
639

liquor, instead of previously reported fast evaporating of the solvent under vacuum [10], afforded needle, colorless, suitable
Scheme 1
crystals for crystallography. The crystallographic data have been deposited at the Cambridge Crystal Structure Database
(CCDC), with CCDC-number 717714, and is freely available upon request from www.ccdc.cam.ac.uk/data_request/cif web
site. Copies of available materials can be obtained free of charge on application to the Director, CCDC, 12 Union Road,
Cambridge CB2 IEZ, UK (fax: (44)01223 336033); e-mail: deposit@ccdc.ac.uk).
1
Compound 2 is a colorless crystalline solid (mp 170°C, reported previously 168-169°C [10]). The H-NMR spectra
were recorded on a Bruker FT-500 spectrometer in chloroform-d , and tetramethylsilane (TMS) was used as an internal
1
1
standard. Mass spectra were registered on a Finnigan Mat TSQ-70 spectrometer. H NMR (δ, ppm): 7.41-7.53 (m, 3H), 7.53-
7.62 (m, 2H), 7.63-7.76 (m, 1H), 7.73-7.80 (m, 1H), 8.14 (dd. 1H), 8.88 (dd, 1H), 8.90-8.94 (m, 1H), 11.60 (s, H NH). MS,
m/z (%): 338 (M+, 11.5), 340 (M++2, 5.3), 303 (38.4), 212 (88.4), 195 (100).
Results and discussion. Single crystal X-ray diffraction. The structure was solved by direct methods using
2
SHELXS-97, and refined by full matrix least squares on F , SHELXL-97 [11]. Minimum and maximum final electron
–3 –3
density was –0.319 e⋅Å and 0.378 e⋅Å . Absorption corrections were performed with the programs X-RED and X-Shape
[12]. Symmetry equivalent reflections were used to optimise crystal shape and size. All non-hydrogen atoms were refined
anisotropically. Aromatic H atoms were placed in calculated positions (C–H = 0.93 Å) and imide H atom was located in
different density maps and treated as riding on the respective carrier atom, with U (H) = 1.2 and 1.5 U (for C and N,
iso eq
respectively). Plots were produced with the Diamond [13] and Mercury programs, and PLATON [14] software was used to
prepare materials for publication.
The title compound was synthesized in a better yield, as compared to the previously proposed structure, by a facile
one-step reaction of 1 and 8-aminoquinoline in the presence of triethylamine. We could get good crystals by slow evaporation
in reaction vessel, using benzene as a solvent. The crystal data and structure refinement details are shown in Table 1. The title
compound crystallizes in the monoclinic crystal system with the C2/c space group. The molecular structure and the atom
numbering design are shown in Fig. 1. All bond lengths and angles are comparable with similar structures, such as the one
reported by Carminski–Zamola, et. al. [3]. The C1–N2 bond distance [1.340(6) Å] is shorter than what expected for a single
bond, indicating its resonance with C=O bond. There is one molecule in the asymmetric unit, which deviates very little from
planarity with an r.m.s of only 0.0477 Å. Three relatively strong non-classical intramolecular hydrogen bonds and a weaker
intermolecular one are present in the structure (Table 2).
Three different types of interactions dominate in stabilizing the crystal structure packing (Figs. 2-4). One is
intermolecular hydrogen bonding between hydrogen atoms from benzyl ring to wards an oxygen atom in the neighboring
i
molecule with 2.47 Å distance between two molecular planes (C14–H14…O1 , with i = x–0.5, y+0.5, z), thus giving rise to
640

Fig. 1. ORTEP diagram of the title compound,
with 50% probability displacement ellipsoids. H
atoms are shown as circled of arbitrary radii.
TABLE 1. Crystal Data and Details of Experiment for 2
Molecular formula
M
C H ClN OS
18 11 2
338.80
T, K
290(2)
Crystal system
a, b, c, Å
β, deg
Monoclinic
14.878(4), 8.4292(15), 25.461(7)
112.022(18)
2960.20(12)
C2/c
3
V, Å
Space group
Z
8
3
d
x
, g/cm
1.520
Crystal size, mm
Color
0.06×0.1×0.29
Colorless
Needle
Crystal shape
Radiation, λ, Å
F(000)
MoK
α
, 0.71073
1392
θ range, deg
1.73-25.68
1.035
2
GOOF on F
h, k, l range
Measured reflections
Independent reflections
Parameters refined
Final R for I > 2σ(I )
R for all data
–18 ≤ h ≤ 18, –10 ≤ k ≤ 10, –30 ≤ l ≤ 30
5452
2717 (Rint = 0.0879)
211
R1 = 0.0752, wR2 = 0.1517
R1 = 0.1343, wR2 = 0.1764
ii
infinite stair-like layered chains (Fig. 2). Another is π-stacking, containing π–π and CH–π interactions (e.g. Cg1–Cg2 =
ii ii
.762 Å, Cg2 –Cg3 = 3.795 Å, Cg3–Cg4 = 3.846 Å, and C2–H2…Cg3iii = 3.875 Å, C18–H18…Cg1 = 3.921 Å, with Cg1
3
being the ring S1/C7/C5/C6/C8, Cg2 = N1/C9/C11/C18/C2/C16, Cg3 = C4/C8/C6/C14/C20/C17 and
Cg4 = C9/C11/C15/C19/C10/C13 with ii = 0.5–x, 0.5–y, –z and iii = –x, –y, –z, iv = 0.5–x, –0.5–y, –z, Fig. 4) between the
inversion side by side symmetric molecules, which cause to hold these parallel neighboring layers together (Fig. 3). There are
two different such parallel layers with an angle of 70.53°, that are in contact with each other by van der Waals interactions,
completing the entire structure packing (Fig. 4).
641

TABLE 2. Hydrogen-Bond Geometry (Å, deg)
D–H…A
D–H
A…H
D…A
D–H…A
N2–H1…Cl1
N2–H1…N1
O1…C10–H10
0.86(6)
0.86(6)
0.93
2.47
2.11
2.27
2.47
3.13
2.65
2.87
3.31
134.3
120.2
122.0
151.8
1
C14–H14…O1
0.93
1
Symmetry code (i) x–0.5, y+0.5, z.
Fig. 2. Showing intermolecular hydrogen bonding and forming a chain.
Fig. 3. π–π and CH–π interactions
between infinite parallel layers.
Fig. 4. Two different parallel
layers with an angle of 70.53°
between the least-squares planes
defined by the two entire
molecules.
Single crystal X-ray structure determination confirmed the earlier proposed structure of 3-chloro-N-(8′-
1
quinolyl)benzo[b]thiophene-2-carboxamide compound and also characterized by HNMR, and Mass spectroscopy. Three
kinds of interactions dominate in the three dimensional crystal structure. Relatively strong intermolecular hydrogen bonds
stick the molecules to an infinite two-dimensional stair-like layered chains. These parallel chains are connected by π–π and
CH–π interactions. There are two such parallel chains, which are in contact by van der Waals interactions, stabilizing the
crystal structure.
We gratefully acknowledge University of Tehran for financial support.
642

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