JOURNAL OF CHEMICAL RESEARCH 2009
JULY, 437-439
RESEARCH
PAPER
437
Crystal structure of 3-chlorobenzo[b]thiophene-2-carbonyl chloride
Sara Tarighia, Alireza Abbasia*, Sara Zamaniana, Alireza Badieia and Mahmood Ghorannevissb
"School of Chemistry, University College of Science, University of Tehran, Tehran, Iran
bPlasma Physics Research Centre, Science
& Research Campus, Islamic Azad University, Tehran, Iran
3-Chlorobenzo[blthiophene-2-carbonyl
chloride was synthesised
from cinnamic
acid and thionyl
chloride.
The single crystal X-ray structure determination
confirmed the earlier proposed structure and the product was
further characterised by lH NMR, 13CNMR and mass spectrometry. The X-ray structure determination revealed two
sets of symmetry related molecules along the b-axis that are loosely connected by relatively weak CH... n (3.626,
3.628 A) interactions, giving rise to two infinite chains. The packing structure is dominated by Van der Waals forces
between these chains. No significant n - 1 l interactions are found in the crystal structure.
Keywords: benzothiophene,
single crystal X-ray diffraction, C-H ... n interaction
details are summarised in Table 1. X-Area program packages were
used for indexing and integrating the single crystal reflections. 13
The structure was solved by direct methods using SHELXS-
97, and refined by full matrix least squares on F2, SHELXL-97.14
Minimum and maximum final electron density was 0.319 and 0.378
eA-3. Absorption correction was performed with the programs X-
RED and X-Shape. ISSymmetry 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
The reaction
chloride and pyridine is a general procedure for the synthesis
of benzothiophene derivatives from readily available starting
materials. These compounds can be easily converted to their
corresponding acids, esters and amines.!-4 Being a heterocyclic
of cinnamic
acid derivatives
with thionyl
compound, benzothiophenes
are useful compounds in research
as a starting material for the synthesis of larger structures that
have special properties such as switching units, excellent
thermal stability and pesticidal activity.5-9 They have also
pharmacological properties as antibiotics, analgesics and enzyme
inhibitors! 0,11 and are found within the chemical structures of
some drugs such as raloxifene,!2 zileuton, and sertaconazole.!O
(C-H
= 0.93 A) and constrained to ride on their parent atoms, with
Uiso(H) = 1.2 Ueq(C). Plots were produced with the Diamondl6 and
Mercury programs, and PLATONI7 software was used to prepare
materials for publication. Crystallographic data have been deposited
at the Cambridge Crystal Structure Database (CCDC), with CCDC-
number 713482. 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).
3-CWorobenzo[b ]tbiophene-2-carbonyl cWoride (I) was synthesised
from cinnamic acid and thionyl cWoride (Scheme I). The molecular
structure of (I) and the atom-numbering scheme are shown in Fig. 1.
The structure contains a benzothiophene molecule that has chloride
and acid chloride substitutions in the thiophenic ring. C I-C2 distance
[1.706(4) A] is significantly shorter than C2-C5 distance [1.417(6)
A], indicating its double nature. The bond length C2-Cll [1.706(4)A],
which is connected to the aromatic thiophene ring, is significantly
shorter than C3-C12 [1.792(5)A, see Table 2], due to the conjugation
between the chloride substituent and the aromatic ring. Otherwise,
3-Chlorobenzo[b]thiophene-2-carbonyl
chloride had been
reported several times by different groups.!-3 For the first time, in
1968, Krubsack and Higa synthesised the title compound with a
very low yield.! After that, in 1970, Nakagawa and co-workers
succeeded to improve a little the yield, from 31.4 to 46%.2
In 1971 Wright and Brabander
better yield (69%) of this structure with a slightly different
synthetic method.3 McKenney and co-workers prepared
the title compound as starting material for several larger
structures.4 None of these groups obtained a crystal structure
obtained
a significantly
a
of the compound,
NMR spectroscopy
and their reports were just based on
and elemental analysis. We have now
synthesised
3-chlorobenzo[b ]thiophene-2-carbonyl
chloride,
Table
compound
1
Crystal data and structure refinement for the title
in part to confirm its structure by getting suitable crystals for
crystallography.
CCDC deposit no.
Molecular formula
Molecular weight
Temperature (K)
713482
gH4CI20S
231.09
C
Experimental
IH and l3C NMR spectra were recorded on
spectrometer.
a Broker FT-500
295(2)
Radiation
A
0.71073
Monoclinic
P 21/c
12.219(4)
3.8909(7)
20.345(6)
913.2(4)
4
1.681
0.12 x 0.15 x 0.44
Yellow
0.888
Thionyl chloride (36.5 mL, 0.5 mol) was added to a stirring solution
of cinnamic acid (14.8 g, 0.1 mol) in chlorobenzene (100 mL).
The resulting suspension was stirred for I hour, and then pyridine
(0.8 mL, O.oJ mol) was added dropwise followed by reflux for 3 days.
The insoluble impurities were then filtered out from the hot solution.
Two different procedures were applied for the crystallisation.
Firstly, the excess solvent of filtration was evaporated under reduced
pressure. The residual solid with 75% yield was dissolved in hexane
for recrystallisation. Extremely fine needle crystals appeared after
two days which were not suitable for crystallography. Secondly,
leaving the resulting solution of chlorobenzene to remain undisturbed
and slow evaporation of the mother liquor afforded suitable crystals
for crystallography. IH NMR (500 MHz, CDCI3): OH (ppm) 7.958(d,
14 Hz, H4), 7.893(d, 17 Hz, Hd, 7.536(t, 14 Hz, H23). l3C NMR
(500 MHz, CDCI3): Oc (ppm) 58.31,140.47,137.20,130.75,126.28,
124.81, 122.85. MS, m/z (%): 309 (M+, 53.5), 232 (M+2, 35.7), 234
(W 4, 7.1), 195 (100), 167 (82).
Crystal system
Space group
a/A
b/A
ciA
v/A3
Z
Deale(g cm-3 )
Crystal size (mm)
Crystal colour
Absorption coefficient (cm-1)
Absorption correction Tminand Tmax 0.6748 and 0.8963
F(OOO)
464
Reflections collected/unique
Range/indices (h, k, I)
e limit n
6028/1555 [Rint= 0.13511
-14,14; -4,4; -24,24
1.77-24.99
1070
No. of observed data, I > 2<J(I)
No. of restraints
The X-ray data were collected at ambient temperature by means
of a STOE IPDS II, using graphite-monochromated Mo Ka radiation
(A = 0.71073 A). No intensity variations due to decomposition of the
crystals were observed. Selected crystallographic and experimental
0
Goodness of fit on F
R1,wR2 [12'2<J(I)la
R1,wR2 (all data)
0.998
0.0576,0.1216
0.0934,0.1427
aRvalues are defined as: R1 = EIIFQI-IFcllj2;lFol
wR2 = [E [w(F 02_Fc 2)21/E [w(F 02) '1]]1/2