Crystal structure of ethyl (E)-2-cyano-3-(thio-phen-2-yl)acrylate: two conformers forming a discrete disorder.

In the title compound, C10H9NO2S, all the non-H atoms, except for the ethyl fragment, lie nearly in the same plane. Despite the mol-ecular planarity, the ethyl fragment presents more than one conformation, giving rise to a discrete disorder, which was modelled with two different crystallographic sites for the eth-oxy O and eth-oxy α-C atoms, with occupancy values of 0.5. In the crystal, the three-dimensional array is mainly directed by C-H⋯(O,N) inter-actions, giving rise to inversion dimers with R22(10) and R22(14) motifs and infinite chains running along the [100] direction.

Chemical context

Cyano­acrylate derivatives are organic compounds with a very important industrial inter­est due to their use as monomers in the production of adhesives and polymer materials (Gololobov & Krylova, 1995 ▸). Furthermore, these compounds have been described as promissory inter­mediates for heterocycle synthesis (Gololobov et al., 1995 ▸) and as nitrile-activated precursors in bioreduction reactions (Winkler et al., 2014 ▸). Still, their most outstanding application is related to their very attractive absorption properties in the UV–Vis region. This capability has been widely described in the literature where cyano­acrylates were employed as precursors for the synthesis of dye-sensitized photovoltaic materials (Chen et al., 2013 ▸; Zietz et al., 2014 ▸; Lee et al., 2009 ▸) and sensors (Zhang et al., 2010 ▸). Considering that the absorption properties are related to the mol­ecular structure of cyano­acrylate compounds (Ma et al., 2014 ▸), it is therefore very useful to know their crystal structures in detail in order to have a better understanding of the link between the structures and properties of these derivatives. In this contribution, we present the crystal structure of a thio­phene-based cyano­acrylate derivative with promising applications in the synthesis of ligands for metal sensing.

Structural commentary

Fig. 1 ▸ shows the mol­ecule of the title compound. The near planarity of the mol­ecule (r.m.s. deviation of 0.006 Å) means that nearly all atoms lie in the same plane perpendicular to [010] except for the ethyl ester fragment (O2/C2/O1/C1/C1A), which presents a discrete disorder due to the existence of two conformations of the ethyl moiety that overlay in the same crystallographic site. This disorder was modelled using two sites for the O1, C1 and C1A atoms with occupancy values of 0.5. The split fragment is observed as a reflection of two ethyl moieties in the two opposite sides of the mirror plane that contains the mol­ecule. These atoms lie, respectively, 0.21 (2), 0.340 (7) and −1.010 (10) Å out of this plane. The planarity allows the formation of a weak intra­molecular C5—H5⋯O2 close contact (Fig. 1 ▸ and Table 1 ▸), which generates an S(6) motif. This mol­ecule is similar to (E)-ethyl-2-cyano-3-(furan-2-yl)acrylate (Kalkhambkar et al., 2012 ▸), differing in the five-membered ring, which is a furanyl in this compound, and presenting a distorted planarity compared with the title compound [dihedral angles of 177.5–179.0° in the two molecules of the asymmetric unit compared with the value of 180.0° in the C6-C5-C3-C2 fragment of the title compound]. Also, no mol­ecular disorder was reported in the furanyl mol­ecule.

Figure 1

The mol­ecular structure of the title compound, showing anisotropic displacement ellipsoids drawn at the 50% probability level. The intra­molecular C—H⋯O hydrogen bond is shown as a dashed line (see Table 1 ▸) and the discrete disorder in the ethyl moiety is also observed.

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5⋯O2	0.93	2.42	2.799 (3)	104
C7—H7⋯O2i	0.93	2.55	3.363 (3)	147
C5—H5⋯O2i	0.93	2.57	3.425 (3)	153
C9—H9⋯N2ii	0.93	2.60	3.520 (4)	172

Symmetry codes: (i) ; (ii) .

Supra­molecular features

In the crystal, the packing is directed by C5—H5⋯O2i and C7—H7⋯O2i [symmetry code: (i) −x + 1, −y + 1, −z] (see Table 1 ▸ and Fig. 2 ▸) inter­actions, which connect pairs of inversion-related mol­ecules, forming slabs of infinite chains running along [100] with (10) and (14) motifs, respectively (see Fig. 2 ▸). These slabs are further linked by weak C9—H9⋯N2ii [symmetry code: (ii) −x, −y + 1, −z] inter­actions along the a-axis direction (Table 1 ▸). Neighboring chains inter­act along [001] direction by van der Waals forces, forming (010) sheets. In the [010] direction, only weak dipolar inter­actions or van der Waals forces act between neighboring sheets to consolidate the three-dimensional array of the crystal structure. Despite the mol­ecular similarity with (E)-ethyl-2-cyano-3-(furan-2-yl)acrylate (Kalkhambkar et al., 2012 ▸), the inversion-related molecules in Kalkhambkar’s structure, joined by similar intermolecular hydrogen bonds, are further connected by different sorts of C—H⋯O and C—H⋯N weaker interactions involving the furanyl ring.

Figure 2

The crystal structure of the title compound, showing the C—H⋯(O, N) hydrogen-bonding inter­actions (dotted lines) along the [100] direction.

Database survey

A search of the Cambridge Structural Database (CSD Version 5.37 with two updates, Groom et al., 2016 ▸) for the complete mol­ecule given the option for any substituent in the five-membered ring and/or allowing a saturated chain longer than the ethyl fragment gave three hits, all of them forming parts of mol­ecules bigger than the title compound, giving different supra­molecular inter­actions due not only to the loss of planarity, as in the case of the ethyl-3-(3-chloro-4-cyano-5-{[4-(di­methyl­amino)­phen­yl]diazen­yl}-2-thien­yl)-2-cyano­acrylate (Xu et al., 2016 ▸), but also due to an increase in the saturated chains as in the case of octyl-2-cyano-3-(4,6-di­bromo-7,7-dimethyl-7H-thieno[3′,4′:4,5]silolo[2,3-b]thio­phen-2-yl)acryl­ate (Liu et al., 2016 ▸) and ethyl-2-cyano-3-(3,3′′′-dihexyl-2,2′:5′,2′′:5′′,2′′′-quaterthio­phen-5-yl)acrylate (Miyazaki et al., 2011 ▸). A search considering any heteroatom in the place of S1 gave six hits. Among them, the more similar compounds correspond to ethyl-(2E)-2-cyano-3-(1-methyl-1H-pyrrol-2-yl)prop-2-enoate (Asiri et al., 2011 ▸), (E)-ethyl-2-cyano-3-(1H-pyrrol-2-yl)acrylate (Yuvaraj et al., 2011 ▸) and (E)-ethyl-2-cyano-3-(furan-2-yl)acrylate (Kalkhambkar et al., 2012 ▸), the last one being the most similar compound since its mol­ecular conformation is also planar, with the ethyl fragment out of the plane and a furanyl forming the five-membered ring.

Synthesis and crystallization

All reagents and solvents were purchased from commercial sources and used as received. In a two-necked round-bottom flask equipped with a condenser, thio­phene-2-carboxaldehyde (740 mg, 6.6 mmol), cyano­acetic acid ethyl ester (753 mg, 6.6 mmol) and piperidine (6,8 µL, 1% mol) were stirred in ethanol for three h. A yellowish brown solid was obtained and recrystallized from ethanol solution (see Fig. 3 ▸). The product was filtered out and then dried under vacuum. The yellowish brown solid was dissolved in methanol and yellow crystals were grown through slow evaporation of the solvent at room temperature with 80% yield. Melting point: 366–367 K, reported: 365–367 K (Jia et al. 2015 ▸). 1H NMR: (DMSO-d 6, 400 MHz, d, ppm): 1,41 (t, 2H), 4,38 (q, 3H), 7.25 (dd, 1H), 7,81 (d, 1H), 7,85 (d, 1H), 8.36 (s, 1H). 13C NMR (DMSO-d, 100 MHz, d, ppm): 14.19, 62.54, 99.3, 115.6, 128.6, 135.1, 136.1, 137.1, 146.6, 162.8.

Figure 3

Schematic representation of the synthetic pathway of ethyl (E)-2-cyano-3-(thio­phen-2-yl)acrylate.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. H atoms were placed in calculated positions (C—H: 0.93–0.97 Å) and included as riding contributions with isotropic displacement parameters set at 1.2–1.5 times the U eq value of the parent atom.

Table 2

Experimental details

Crystal data
Chemical formula	C10H9NO2S
M r	207.24
Crystal system, space group	Monoclinic, C2/m
Temperature (K)	298
a, b, c (Å)	13.637 (2), 6.8965 (16), 11.817 (3)
β (°)	109.28 (2)
V (Å3)	1049.0 (4)
Z	4
Radiation type	Mo Kα
μ (mm−1)	0.28
Crystal size (mm)	0.19 × 0.12 × 0.07
Data collection
Diffractometer	Agilent SuperNova, Dual, Cu at zero, Atlas
Absorption correction	Multi-scan (CrysAlis PRO; Agilent, 2014 ▸)
T min, T max	0.760, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	9896, 1171, 1049
R int	0.068
(sin θ/λ)max (Å−1)	0.625
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.047, 0.126, 1.14
No. of reflections	1171
No. of parameters	96
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	0.35, −0.24

Computer programs: CrysAlis PRO (Agilent, 2014 ▸), SUPERFLIP (Palatinus & Chapuis, 2007 ▸), SHELXL2014 (Sheldrick, 2015 ▸) and Mercury (Macrae et al., 2008 ▸).

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989017010799/ff2150sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989017010799/ff2150Isup2.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S2056989017010799/ff2150Isup3.cml

CCDC reference: 1563845

Additional supporting information: crystallographic information; 3D view; checkCIF report

C10H9NO2S	F(000) = 432
Mr = 207.24	Dx = 1.312 Mg m−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
a = 13.637 (2) Å	Cell parameters from 2818 reflections
b = 6.8965 (16) Å	θ = 4.5–26.3°
c = 11.817 (3) Å	µ = 0.28 mm−1
β = 109.28 (2)°	T = 298 K
V = 1049.0 (4) Å3	Parallelepiped, yellow
Z = 4	0.19 × 0.12 × 0.07 mm

Agilent SuperNova, Dual, Cu at zero, Atlas diffractometer	1171 independent reflections
Radiation source: SuperNova (Mo) X-ray Source	1049 reflections with I > 2σ(I)
Detector resolution: 5.3072 pixels mm-1	Rint = 0.068
ω scans	θmax = 26.4°, θmin = 3.1°
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2014)	h = −16→16
Tmin = 0.760, Tmax = 1.000	k = −8→8
9896 measured reflections	l = −14→14

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.047	H-atom parameters constrained
wR(F2) = 0.126	w = 1/[σ2(Fo2) + (0.053P)2 + 0.7374P] where P = (Fo2 + 2Fc2)/3
S = 1.14	(Δ/σ)max < 0.001
1171 reflections	Δρmax = 0.35 e Å−3
96 parameters	Δρmin = −0.24 e Å−3
0 restraints	Extinction correction: SHELXL2016 (Sheldrick, 2016), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: iterative	Extinction coefficient: 0.007 (2)

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.

	x	y	z	Uiso*/Ueq	Occ. (<1)
S1	0.11266 (5)	0.500000	−0.02961 (7)	0.0560 (3)
N2	0.2293 (2)	0.500000	0.2653 (2)	0.0733 (9)
O2	0.53999 (15)	0.500000	0.1743 (2)	0.0732 (7)
C2	0.4730 (2)	0.500000	0.2195 (3)	0.0568 (7)
C3	0.36045 (19)	0.500000	0.1505 (2)	0.0480 (6)
C4	0.2879 (2)	0.500000	0.2153 (3)	0.0531 (7)
C7	0.2120 (2)	0.500000	−0.1795 (3)	0.0555 (7)
H7	0.264802	0.500000	−0.213002	0.067*
C6	0.22929 (19)	0.500000	−0.0583 (2)	0.0470 (6)
C5	0.33082 (19)	0.500000	0.0298 (2)	0.0468 (6)
H5	0.385193	0.500000	−0.001307	0.056*
C8	0.1056 (2)	0.500000	−0.2475 (3)	0.0630 (8)
H8	0.080614	0.500000	−0.330873	0.076*
C9	0.0436 (2)	0.500000	−0.1786 (3)	0.0616 (8)
H9	−0.028547	0.500000	−0.209250	0.074*
O1	0.48964 (18)	0.531 (3)	0.3371 (2)	0.064 (3)	0.5
C1	0.5976 (3)	0.5493 (10)	0.4143 (4)	0.073 (3)	0.5
H1A	0.600898	0.615277	0.487917	0.088*	0.5
H1B	0.636145	0.625544	0.374142	0.088*	0.5
C1A	0.6446 (5)	0.3535 (15)	0.4422 (6)	0.127 (3)	0.5
H1AA	0.641144	0.288738	0.369077	0.191*	0.5
H1AB	0.607205	0.279578	0.483442	0.191*	0.5
H1AC	0.715902	0.365498	0.492230	0.191*	0.5

	U11	U22	U33	U12	U13	U23
S1	0.0331 (4)	0.0805 (6)	0.0559 (5)	0.000	0.0168 (3)	0.000
N2	0.0468 (14)	0.122 (3)	0.0570 (16)	0.000	0.0246 (12)	0.000
O2	0.0353 (10)	0.130 (2)	0.0567 (13)	0.000	0.0184 (9)	0.000
C2	0.0379 (14)	0.082 (2)	0.0506 (16)	0.000	0.0144 (12)	0.000
C3	0.0353 (13)	0.0627 (16)	0.0477 (15)	0.000	0.0161 (11)	0.000
C4	0.0373 (13)	0.0740 (19)	0.0472 (15)	0.000	0.0127 (12)	0.000
C7	0.0428 (14)	0.0724 (19)	0.0527 (16)	0.000	0.0179 (12)	0.000
C6	0.0334 (12)	0.0580 (15)	0.0512 (15)	0.000	0.0161 (11)	0.000
C5	0.0332 (12)	0.0559 (15)	0.0530 (15)	0.000	0.0167 (11)	0.000
C8	0.0491 (16)	0.088 (2)	0.0462 (16)	0.000	0.0074 (12)	0.000
C9	0.0368 (14)	0.079 (2)	0.0622 (18)	0.000	0.0069 (13)	0.000
O1	0.0410 (11)	0.103 (10)	0.0458 (12)	−0.003 (2)	0.0122 (9)	−0.008 (2)
C1	0.046 (2)	0.112 (9)	0.055 (2)	−0.005 (2)	0.0070 (17)	−0.019 (3)
C1A	0.093 (5)	0.188 (9)	0.077 (4)	0.053 (5)	−0.004 (3)	−0.019 (5)

S1—C9	1.700 (3)	C5—H5	0.9300
S1—C6	1.732 (3)	C8—C9	1.354 (5)
N2—C4	1.139 (4)	C8—H8	0.9300
O2—C2	1.200 (3)	C9—H9	0.9300
C2—O1	1.350 (5)	O1—C1	1.459 (5)
C2—C3	1.482 (4)	C1—C1A	1.485 (11)
C3—C5	1.347 (4)	C1—H1A	0.9700
C3—C4	1.437 (4)	C1—H1B	0.9700
C7—C6	1.372 (4)	C1A—H1AA	0.9600
C7—C8	1.407 (4)	C1A—H1AB	0.9600
C7—H7	0.9300	C1A—H1AC	0.9600
C6—C5	1.431 (4)
C9—S1—C6	91.57 (14)	C9—C8—H8	123.6
O2—C2—O1	124.3 (3)	C7—C8—H8	123.6
O2—C2—C3	123.9 (3)	C8—C9—S1	112.4 (2)
O1—C2—C3	111.0 (2)	C8—C9—H9	123.8
C5—C3—C4	123.0 (2)	S1—C9—H9	123.8
C5—C3—C2	118.5 (2)	C2—O1—C1	116.7 (3)
C4—C3—C2	118.5 (2)	O1—C1—C1A	109.5 (8)
N2—C4—C3	179.1 (3)	O1—C1—H1A	109.8
C6—C7—C8	112.7 (3)	C1A—C1—H1A	109.8
C6—C7—H7	123.6	O1—C1—H1B	109.8
C8—C7—H7	123.6	C1A—C1—H1B	109.8
C7—C6—C5	123.4 (2)	H1A—C1—H1B	108.2
C7—C6—S1	110.6 (2)	C1—C1A—H1AA	109.5
C5—C6—S1	126.0 (2)	C1—C1A—H1AB	109.5
C3—C5—C6	130.5 (3)	H1AA—C1A—H1AB	109.5
C3—C5—H5	114.7	C1—C1A—H1AC	109.5
C6—C5—H5	114.7	H1AA—C1A—H1AC	109.5
C9—C8—C7	112.8 (3)	H1AB—C1A—H1AC	109.5
O2—C2—C3—C5	0.000 (1)	C2—C3—C5—C6	180.000 (1)
O1—C2—C3—C5	170.1 (8)	C7—C6—C5—C3	180.000 (1)
O2—C2—C3—C4	180.000 (1)	S1—C6—C5—C3	0.000 (1)
O1—C2—C3—C4	−9.9 (8)	C6—C7—C8—C9	0.000 (1)
C8—C7—C6—C5	180.000 (1)	C7—C8—C9—S1	0.000 (1)
C8—C7—C6—S1	0.000 (1)	C6—S1—C9—C8	0.000 (1)
C9—S1—C6—C7	0.000 (1)	O2—C2—O1—C1	−5.6 (17)
C9—S1—C6—C5	180.0	C3—C2—O1—C1	−175.6 (9)
C4—C3—C5—C6	0.000 (1)	C2—O1—C1—C1A	−79.5 (13)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···O2	0.93	2.42	2.799 (3)	104
C7—H7···O2i	0.93	2.55	3.363 (3)	147
C5—H5···O2i	0.93	2.57	3.425 (3)	153
C9—H9···N2ii	0.93	2.60	3.520 (4)	172