organic compounds
1-Vinyl-4-imidazoline-2-thione
aUniversity of Innsbruck, Faculty of Chemistry and Pharmacy, Innrain 80-82, 6020 Innsbruck, Austria
*Correspondence e-mail: herwig.schottenberger@uibk.ac.at
The title compound, C5H6N2S, was obtained by deprotonation of 1-vinylimidazole and subsequent reaction with elemental sulfur. In the crystal, the molecules are linked by N—H⋯S and C—H⋯S hydrogen bonds, and arranged in layers parallel to the ab plane.
Keywords: crystal structure; imidazole; thione; vinyl.
CCDC reference: 1570185
Structure description
Imidazoline-2-thiones (Laus et al., 2013) are versatile and easy-to-synthesize building blocks. The title compound is one of the small molecules whose structure, surprisingly, has not yet been described. Not only is the molecule itself interesting, it also allows further derivatization at the S and N atoms (Hummel et al., 2017; Oberparleiter et al., 2016), and gives access to a plethora of functionalized imidazolium salts. The primary alkylation takes place at the S atom; the resulting salt can then be deprotonated to yield a neutral 2-alkylsulfanyl-1-vinylimidazole, which can then be transformed into a quaternary salt. In addition, the vinyl substituent renders the molecule polymerizable and thus permits a path to imidazole-based polymers (Anderson & Long, 2010; Nakabayashi & Mori, 2013).
The synthesis of the title compound involves deprotonation of 1-vinylimidazole and subsequent reaction with elemental sulfur. Strong bases, such as isopropylmagnesium chloride or hexyllithium, are required. Other reaction conditions, such as sulfur in KOH/DMSO (Yuan et al., 2010), K2CO3/MeOH (Ansell et al., 1970) or Et3N/pyridine (Becker et al., 1973), did not yield the desired product.
The C=S bond length of 1.688 (1) Å is in agreement with the accepted value of 1.68±0.02 Å for imidazoline-2-thiones (Laus et al., 2013), ruling out the possibility of a thiol tautomer. The molecular structure is depicted in Fig. 1. The imidazoline-2-thione molecules are linked by N—H⋯S and C—H⋯S hydrogen bonds (Table 1) to form layers, which are arranged parallel to the ab plane (Fig. 2).
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Related structures, such as 3-(1H,1H,2H,2H-perfluorooctyl)-1-vinylimidazoline-2-thione (Partl, Laus, Gelbrich et al., 2017) and 3,3′-(hexane-1,6-diyl)bis(1-vinylimidazoline-2-thione) (Partl, Laus, Kahlenberg et al., 2017), have been reported recently. Polymorphs of the analogous 1-methylimidazoline-2-thione (`methimazole') have been described (Lodochnikova et al., 2013).
Synthesis and crystallization
Method A: isopropylmagnesium chloride solution (10 ml, 2 M in Et2O, 20.0 mmol) was added to a solution of 1-vinylimidazole (1.52 g, 16.1 mmol) in anhydrous tetrahydrofuran (THF; 15 ml), and the mixture was stirred for 17 h under an argon atmosphere. Elemental sulfur (573 mg, 17.9 mmol) was added to the clear solution and stirring was continued at room temperature. After 28 h, H2O (20 ml) was added and acidified with HCl (30 ml, 1 M, 30.0 mmol). The mixture was extracted with chloroform (3 × 40 ml). The combined organic phases were washed with H2O (2 × 60 ml). The solvent was removed under reduced pressure, yielding 1.43 g (70%) of 1-vinylimidazoline-2-thione as an off-white solid.
Method B: n-hexyllithium (16 ml, 2.3 M in hexanes, 36.8 mmol) was added to a cooled (193 K) solution of 1-vinylimidazole (3.07 g, 32.6 mmol) in anhydrous THF (40 ml) under an argon atmosphere. The mixture was stirred for 2 h at 195 K and then for 1 h at 263 K. Sulfur (1.1 g, 34.2 mmol) was added and stirring was continued for 68 h. The reaction was quenched with H2O (20 ml) and acidified with HCl (51 ml, 1 M, 51.0 mmol). The THF was removed under reduced pressure, and the residue was extracted with CHCl3 (3 × 100 ml) and with EtOAc (100 ml). The combined organic phases were washed with H2O (100 ml). The solution was treated with followed by filtration over celite. The solvent was removed under reduced pressure and the product dried overnight at high vacuum, yielding 2.2 g (54%) of 1-vinylimidazoline-2-thione as an off-white solid. Single crystals were obtained by slow evaporation of a solution in CHCl3 (m.p. 416–418 K; above 396 K). The PXRD (Mo Kα radiation) of the bulk material was an excellent match to that calculated from the single-crystal diffraction data (Fig. 3), indicating phase purity.
1H NMR (300 MHz, DMSO-d6): δ 12.35 (s, 1H), 7.52 (t, J = 2.1 Hz, 1H), 7.38 (dd, J = 16.1, 9.1 Hz, 1H), 7.04 (t, J = 2.6 Hz, 1H), 5.43 (dd, J = 16.2, 1.3 Hz, 1H), 4.92 (dd, J = 9.1, 1.4 Hz, 1H). 13C NMR (75 MHz, DMSO-d6): δ 161.8, 129.0, 116.3, 113.8, 101.0. IR (neat): ν 3120, 3108, 3006, 1646, 1568, 1462, 1414, 1285, 1267, 1244, 1122, 1090, 1022, 960, 875, 772, 742, 682, 651, 545, 491 cm−1.
Refinement
The H atom at N2 was found and refined isotropically with an N—H bond-length restraint of 0.87 (2) Å. Crystal data, data collection and structure .
details are summarized in Table 2Structural data
CCDC reference: 1570185
https://doi.org/10.1107/S241431461701207X/qm4003sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S241431461701207X/qm4003Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S241431461701207X/qm4003Isup3.mol
Supporting information file. DOI: https://doi.org/10.1107/S241431461701207X/qm4003Isup4.cml
Data collection: APEX2 (Bruker, 2014); cell
SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: XT in SHELXTL (Bruker, 2014); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: Mercury (Macrae et al., 2008).C5H6N2S | Dx = 1.387 Mg m−3 |
Mr = 126.18 | Melting point: 418 K |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 10.7775 (3) Å | Cell parameters from 9910 reflections |
b = 9.6848 (3) Å | θ = 2.9–26.4° |
c = 12.1792 (4) Å | µ = 0.42 mm−1 |
β = 108.139 (1)° | T = 173 K |
V = 1208.06 (6) Å3 | Prism, colourless |
Z = 8 | 0.17 × 0.12 × 0.07 mm |
F(000) = 528 |
Bruker D8 QUEST PHOTON 100 diffractometer | 1187 independent reflections |
Radiation source: Incoatec Microfocus | 1114 reflections with I > 2σ(I) |
Multi layered optics monochromator | Rint = 0.026 |
Detector resolution: 10.4 pixels mm-1 | θmax = 26.0°, θmin = 2.9° |
φ and ω scans | h = −13→13 |
Absorption correction: multi-scan (SADABS; Bruker, 2014) | k = −11→11 |
Tmin = 0.864, Tmax = 0.911 | l = −15→15 |
16916 measured reflections |
Refinement on F2 | Hydrogen site location: mixed |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.024 | w = 1/[σ2(Fo2) + (0.0314P)2 + 1.0869P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.065 | (Δ/σ)max < 0.001 |
S = 1.08 | Δρmax = 0.24 e Å−3 |
1187 reflections | Δρmin = −0.22 e Å−3 |
78 parameters | Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
1 restraint | Extinction coefficient: 0.0068 (9) |
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. |
Refinement. Hydrogen atom at N2 were found and refined isotropically with bond restraint (d=87pm). |
x | y | z | Uiso*/Ueq | ||
S1 | 0.11344 (3) | 0.54728 (4) | 0.42718 (3) | 0.02539 (14) | |
N1 | 0.31623 (10) | 0.38500 (11) | 0.41324 (9) | 0.0200 (2) | |
N2 | 0.17797 (11) | 0.43417 (12) | 0.24678 (9) | 0.0225 (2) | |
H2N | 0.1110 (15) | 0.4659 (17) | 0.1942 (13) | 0.034 (4)* | |
C1 | 0.20309 (12) | 0.45566 (12) | 0.36118 (11) | 0.0192 (3) | |
C2 | 0.35897 (13) | 0.32017 (14) | 0.32890 (11) | 0.0241 (3) | |
H2 | 0.4349 | 0.2647 | 0.3421 | 0.029* | |
C3 | 0.27288 (13) | 0.35079 (14) | 0.22622 (11) | 0.0250 (3) | |
H3 | 0.2762 | 0.3209 | 0.1529 | 0.030* | |
C4 | 0.37875 (13) | 0.38285 (14) | 0.53361 (11) | 0.0262 (3) | |
H4 | 0.3320 | 0.4176 | 0.5821 | 0.031* | |
C5 | 0.49716 (14) | 0.33608 (16) | 0.58291 (12) | 0.0327 (3) | |
H5A | 0.5466 | 0.3006 | 0.5369 | 0.039* | |
H5B | 0.5335 | 0.3376 | 0.6647 | 0.039* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.01913 (19) | 0.0318 (2) | 0.0239 (2) | 0.00659 (12) | 0.00469 (13) | −0.00509 (12) |
N1 | 0.0173 (5) | 0.0214 (5) | 0.0203 (5) | 0.0030 (4) | 0.0045 (4) | 0.0000 (4) |
N2 | 0.0179 (5) | 0.0267 (6) | 0.0197 (5) | 0.0030 (4) | 0.0014 (4) | −0.0020 (4) |
C1 | 0.0159 (6) | 0.0192 (6) | 0.0213 (6) | −0.0016 (4) | 0.0042 (5) | −0.0007 (4) |
C2 | 0.0215 (6) | 0.0253 (7) | 0.0260 (7) | 0.0045 (5) | 0.0081 (5) | −0.0034 (5) |
C3 | 0.0226 (6) | 0.0280 (7) | 0.0244 (7) | 0.0015 (5) | 0.0074 (5) | −0.0055 (5) |
C4 | 0.0277 (7) | 0.0303 (7) | 0.0199 (6) | 0.0060 (5) | 0.0066 (5) | 0.0020 (5) |
C5 | 0.0319 (8) | 0.0397 (8) | 0.0227 (7) | 0.0104 (6) | 0.0028 (6) | 0.0026 (6) |
S1—C1 | 1.6884 (13) | C2—C3 | 1.3380 (19) |
N1—C1 | 1.3695 (16) | C2—H2 | 0.9500 |
N1—C2 | 1.3986 (16) | C3—H3 | 0.9500 |
N1—C4 | 1.4102 (16) | C4—C5 | 1.3104 (19) |
N2—C1 | 1.3502 (16) | C4—H4 | 0.9500 |
N2—C3 | 1.3858 (17) | C5—H5A | 0.9500 |
N2—H2N | 0.859 (14) | C5—H5B | 0.9500 |
C1—N1—C2 | 109.49 (10) | N1—C2—H2 | 126.4 |
C1—N1—C4 | 123.85 (11) | C2—C3—N2 | 107.24 (11) |
C2—N1—C4 | 126.64 (11) | C2—C3—H3 | 126.4 |
C1—N2—C3 | 110.74 (11) | N2—C3—H3 | 126.4 |
C1—N2—H2N | 124.5 (11) | C5—C4—N1 | 124.29 (13) |
C3—N2—H2N | 124.7 (11) | C5—C4—H4 | 117.9 |
N2—C1—N1 | 105.33 (11) | N1—C4—H4 | 117.9 |
N2—C1—S1 | 127.71 (10) | C4—C5—H5A | 120.0 |
N1—C1—S1 | 126.95 (10) | C4—C5—H5B | 120.0 |
C3—C2—N1 | 107.21 (11) | H5A—C5—H5B | 120.0 |
C3—C2—H2 | 126.4 | ||
C3—N2—C1—N1 | 0.31 (14) | C1—N1—C2—C3 | −0.01 (15) |
C3—N2—C1—S1 | −178.63 (10) | C4—N1—C2—C3 | −178.69 (12) |
C2—N1—C1—N2 | −0.18 (14) | N1—C2—C3—N2 | 0.19 (15) |
C4—N1—C1—N2 | 178.55 (11) | C1—N2—C3—C2 | −0.32 (15) |
C2—N1—C1—S1 | 178.77 (10) | C1—N1—C4—C5 | −167.81 (14) |
C4—N1—C1—S1 | −2.51 (18) | C2—N1—C4—C5 | 10.7 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2N···S1i | 0.86 (1) | 2.54 (1) | 3.378 (1) | 167 (1) |
C2—H2···S1ii | 0.95 | 2.82 | 3.728 (1) | 160 |
Symmetry codes: (i) −x, y, −z+1/2; (ii) x+1/2, y−1/2, z. |
Acknowledgements
We are grateful to Barbara Schmidt for technical assistance.
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