3-Bromo­methyl-5-chloro-2-benzothio­phene

The title compound, C₉H₆BrClS, was synthesized in a search for new benzothio­phene compounds with potentially high bioactivity. In the crystal packing, a weak Br...Cl inter­action is present.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C)= 0.004 Å
• R factor = 0.028
• wR factor = 0.075
• Data-to-parameter ratio = 16.7

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S1. Comment

Benzo[b]thiophene derivatives have attracted much interest in organic chemistry (Bianchini & Meli, 1997; Cabiddu et al., 2002) because of their pharmacological activities and chemical properties. They display antibiotic, analgesic, anti-exudative, anti-inflammatory and diuretic activities, and are widely used in the synthesis of thioindigo dyes. In order to search for new benzothiophene compounds with potentially high bioactivity, we have synthesized the title compound, (I), and report its crystal structure here.

The molecular structure of (I) is shown in Fig. 1. The benzothiophene ring system is planar, the maximum deviation from planarity being 0.012 (3) Å for atom C7. Bond lengths and angles (Table 1) are within expected ranges, with the C—S bonds averaging 1.726 (3) Å.

In the crystal packing (Fig. 2), a weak Br···Cl contact [Br1···Cl1ⁱ 3.683 (1) Å; symmetry code: (i) 1 − x, −1/2 + y, 1/2 − z] is observed. No significant hydrogen-bonding or π–π interactions are present.

S2. Experimental

The title compound was prepared according to the method described by Cabiddu et al. (2002). 4-Chlorothiophene (10 mmol) and KOH (11 mmol) were dissolved in EtOH (5 ml) and H₂O (5 ml) at room temperature, then BrCH₂COCH₃ (10 mmol) and ethyl acetate (20 ml) were added dropwise. The mixture was stirred magnetically for 2 h and the resulting white solid product, (4-chlorophenylthio)acetone, was purified by preparative thin-layer chromatography on silica gel with cyclohexane and ethyl acetate (10:1) as eluent. Polyphosphoric acid (PPA, 2.5 mmol) and (4-chlorophenylthio)acetone (3 mmol) were added to dimethylbenzene (5 ml) under a nitrogen atmosphere. The mixture was refluxed for 1 h to give 5-chloro-3-methylthianaphthene. The title compound was prepared by reaction of N-bromosuccinimide (3 mmol) with 5-chloro-3-methylthianaphthene (2 mmol) at 393 K for 3 h, and purified by column chromatography (hexane–EtOAc, 5:1) (yield 85%) (Nandi et al., 2002; Hessian & Flynn, 2003). Single crystals of (I) suitable for X-ray analysis were obtained by slow evaporation at 298 K of a 4:1 (v/v) ethyl acetate–petroleum ether solution. Spectroscopic analysis: IR (KBr, ν, cm⁻¹): 3008, 2898, 1780, 1080, 817; ¹H NMR (CDCl₃, δ, p.p.m.): 7.63 (m, 2H), 7.26 (m, 2H), 4.82 (s, 2H).

S3. Refinement

All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H distances in the range 0.95–1.00 Å and U_iso(H) = 1.2_Ueq(C).

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Bruker, 2002); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A packing diagram of compound (I), viewed down the a axis.

3-Bromomethyl-5-chloro-2-benzothiophene

Crystal data

C9H6BrClS	F(000) = 512
Mr = 261.56	Dx = 1.867 Mg m^−3
Monoclinic, P21/c	Melting point: 409 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 7.2891 (9) Å	Cell parameters from 3579 reflections
b = 13.6044 (16) Å	θ = 1.9–25.3°
c = 9.4539 (12) Å	µ = 4.86 mm^−1
β = 96.946 (2)°	T = 298 K
V = 930.6 (2) Å^3	Prism, colourless
Z = 4	0.28 × 0.20 × 0.13 mm

Data collection

Bruker SMART CCD area-detector diffractometer	1823 independent reflections
Radiation source: fine-focus sealed tube	1566 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.016
ϕ and ω scans	θmax = 26.0°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Bruker, 2002)	h = −8→8
Tmin = 0.325, Tmax = 0.530	k = −16→14
5138 measured reflections	l = −9→11

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.075	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0423P)^2 + 0.2265P] where P = (Fo^2 + 2Fc^2)/3
1823 reflections	(Δ/σ)max = 0.001
109 parameters	Δρmax = 0.34 e Å^−3
0 restraints	Δρmin = −0.53 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.65145 (4)	0.18964 (2)	−0.02590 (3)	0.05367 (13)
Cl1	0.60567 (10)	0.56974 (6)	0.26136 (10)	0.0652 (2)
S1	1.29663 (9)	0.33864 (6)	0.12678 (8)	0.04961 (19)
C1	1.1176 (3)	0.40894 (18)	0.1780 (3)	0.0374 (5)
C2	0.9491 (3)	0.38833 (17)	0.0921 (2)	0.0346 (5)
C3	0.7899 (3)	0.43886 (18)	0.1185 (3)	0.0385 (5)
H3	0.6773	0.4268	0.0638	0.046*
C4	0.8028 (3)	0.50625 (18)	0.2260 (3)	0.0420 (6)
C5	0.9682 (4)	0.5268 (2)	0.3107 (3)	0.0476 (6)
H5	0.9718	0.5736	0.3827	0.057*
C6	1.1265 (4)	0.4771 (2)	0.2869 (3)	0.0457 (6)
H6	1.2377	0.4894	0.3433	0.055*
C7	1.1484 (4)	0.2825 (2)	−0.0039 (3)	0.0477 (6)
H7	1.1868	0.2343	−0.0636	0.057*
C8	0.9719 (4)	0.31392 (17)	−0.0126 (3)	0.0391 (5)
C9	0.8203 (4)	0.2768 (2)	−0.1173 (3)	0.0492 (6)
H9A	0.8722	0.2408	−0.1916	0.059*
H9B	0.7509	0.3319	−0.1613	0.059*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.04749 (19)	0.0526 (2)	0.0589 (2)	−0.00305 (11)	−0.00180 (13)	−0.00422 (12)
Cl1	0.0537 (4)	0.0572 (4)	0.0882 (6)	0.0100 (3)	0.0235 (4)	−0.0142 (4)
S1	0.0355 (3)	0.0558 (4)	0.0577 (4)	0.0060 (3)	0.0058 (3)	0.0009 (3)
C1	0.0339 (12)	0.0387 (13)	0.0404 (13)	−0.0019 (9)	0.0080 (10)	0.0071 (10)
C2	0.0368 (12)	0.0341 (12)	0.0334 (12)	−0.0010 (9)	0.0057 (9)	0.0061 (10)
C3	0.0348 (12)	0.0395 (13)	0.0413 (13)	−0.0007 (10)	0.0046 (10)	0.0034 (10)
C4	0.0416 (13)	0.0359 (13)	0.0512 (15)	0.0010 (10)	0.0159 (11)	−0.0006 (11)
C5	0.0543 (16)	0.0424 (14)	0.0475 (16)	−0.0074 (12)	0.0119 (12)	−0.0074 (12)
C6	0.0432 (14)	0.0498 (15)	0.0434 (15)	−0.0092 (12)	0.0019 (11)	−0.0022 (12)
C7	0.0477 (15)	0.0503 (15)	0.0468 (16)	0.0056 (12)	0.0122 (12)	−0.0044 (12)
C8	0.0434 (14)	0.0410 (13)	0.0338 (12)	0.0019 (10)	0.0091 (10)	0.0021 (10)
C9	0.0539 (16)	0.0548 (15)	0.0390 (14)	0.0003 (13)	0.0057 (12)	−0.0029 (12)

Geometric parameters (Å, º)

Br1—C9	1.981 (3)	C4—C5	1.393 (4)
Cl1—C4	1.744 (3)	C5—C6	1.379 (4)
S1—C7	1.719 (3)	C5—H5	0.9300
S1—C1	1.734 (2)	C6—H6	0.9300
C1—C6	1.382 (4)	C7—C8	1.349 (4)
C1—C2	1.416 (3)	C7—H7	0.9300
C2—C3	1.397 (3)	C8—C9	1.481 (4)
C2—C8	1.440 (3)	C9—H9A	0.9700
C3—C4	1.363 (4)	C9—H9B	0.9700
C3—H3	0.9300
C7—S1—C1	90.97 (12)	C5—C6—C1	119.1 (2)
C6—C1—C2	121.3 (2)	C5—C6—H6	120.5
C6—C1—S1	127.56 (19)	C1—C6—H6	120.5
C2—C1—S1	111.16 (18)	C8—C7—S1	114.5 (2)
C3—C2—C1	118.8 (2)	C8—C7—H7	122.7
C3—C2—C8	129.5 (2)	S1—C7—H7	122.7
C1—C2—C8	111.6 (2)	C7—C8—C2	111.7 (2)
C4—C3—C2	118.7 (2)	C7—C8—C9	124.2 (2)
C4—C3—H3	120.7	C2—C8—C9	124.1 (2)
C2—C3—H3	120.7	C8—C9—Br1	111.44 (18)
C3—C4—C5	122.8 (2)	C8—C9—H9A	109.3
C3—C4—Cl1	119.5 (2)	Br1—C9—H9A	109.3
C5—C4—Cl1	117.8 (2)	C8—C9—H9B	109.3
C6—C5—C4	119.4 (2)	Br1—C9—H9B	109.3
C6—C5—H5	120.3	H9A—C9—H9B	108.0
C4—C5—H5	120.3
C7—S1—C1—C6	179.0 (2)	C4—C5—C6—C1	0.9 (4)
C7—S1—C1—C2	−0.8 (2)	C2—C1—C6—C5	−0.9 (4)
C6—C1—C2—C3	0.4 (4)	S1—C1—C6—C5	179.4 (2)
S1—C1—C2—C3	−179.80 (17)	C1—S1—C7—C8	0.6 (2)
C6—C1—C2—C8	−179.0 (2)	S1—C7—C8—C2	−0.2 (3)
S1—C1—C2—C8	0.8 (3)	S1—C7—C8—C9	179.6 (2)
C1—C2—C3—C4	0.0 (3)	C3—C2—C8—C7	−179.7 (2)
C8—C2—C3—C4	179.3 (2)	C1—C2—C8—C7	−0.4 (3)
C2—C3—C4—C5	0.0 (4)	C3—C2—C8—C9	0.5 (4)
C2—C3—C4—Cl1	−179.67 (18)	C1—C2—C8—C9	179.8 (2)
C3—C4—C5—C6	−0.4 (4)	C7—C8—C9—Br1	106.3 (3)
Cl1—C4—C5—C6	179.2 (2)	C2—C8—C9—Br1	−73.9 (3)