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organic papers
Acta Crystallographica Section E

Structure Reports Online
ISSN 1600-5368

4-Benzoyl-5-(4-chlorophenyl)-2-(methylsulfanyl)1H-imidazole

Dmitry V. Albov,* Victor B. Rybakov, Eugene V. Babaev and Alexander A. Tsisevich
Department of Chemistry, Moscow State University, 119992 Moscow, Russian Federation Correspondence e-mail: albov@struct.chem.msu.ru

The title imidazole, C17H13ClN2OS, was obtained by unusual rearrangement of the pyrimidinium salt. The structure was characterized by 1H NMR spectroscopy and X-ray diffraction. A mechanism of transformation (pyrimidinium salt ! title imidazole) is proposed.

Received 27 January 2006 Accepted 2 February 2006

Comment
We observed the unusual formation of the title substituted imidazole, (1), in the reaction of the pyrimidinium salt (2) with a secondary amine.

Key indicators Single-crystal X-ray study T = 293 K А Mean (C-C) = 0.004 A R factor = 0.048 wR factor = 0.059 Data-to-parameter ratio = 15.9 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

# 2006 International Union of Crystallography All rights reserved

Although the general class of N-phenacyl-2-(methylsulfanyl)pyrimidinium salts is known (Liebscher & Hassoun, 1988), few data are available on their reactivity. As was reported by Liebscher & Hassoun (1988), salts like (2) react with pyridine, leading to oxazolo[3,2-a]pyrimidinium salts. The suggested structure of imidazole (1) was proved by elemental analysis, X-ray diffraction, and NMR and mass spectroscopy. According to the 1H NMR data, there are two NH peaks as well as two SMe singlets, and this clearly confirms that the imidazole exists as the expected mixture of two NH tautomers. However, only one tautomer, namely the 4benzoyl-5-(4-chlorophenyl)-1H tautomer, is visible in the single-crystal structure according to the X-ray data. The five-membered heterocycle (N1/C2/N3/C4/C5) (Fig. 1) is nearly planar and the attached chlorophenyl ring (C13 C18) makes a dihedral angle of 36.0 (1) . The second phenyl ring (C7 C12) of the benzoyl group forms a dihedral angle of 50.6 (1) with the five-membered heterocycle, indicating a low degree of conjugation between these rings. This phenomenon may be explained by steric effects of the packing of both phenyl rings. An N HСССN intermolecular hydrogen bond (Table 2) links the molecules in the crystal structure into extended chains (Fig. 2). From the formal viewpoint, the structure of (1) has two C atoms fewer than (2). The mechanism of this unexpected transformation may be rationalized in terms of rearrangement of pyrimidine to imidazole. Indeed, if the secondary amine
doi:10.1107/S1600536806004120 Albov et al.


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caused ring cleavage leading to open form (3), the methylene group of the intermediate, (3), is acidic enough to lose a proton, giving the anion (4). In this case, the closure of the five-membered ring [intermediate (5)] may naturally follow from the polarity distribution along the chain. Final aromatization of the imidazole ring is associated with the elimination of the stable group the enamine of the acetaldehyde from (5) to (1).

Figure 1
The molecular structure of (1) and the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

Experimental
The pyrimidinium salt, (2), was obtained by the published method of Liebscher & Hassoun (1988). To synthesize compound (1), piperidine (2 ml, 0.02 mmol) was added to a suspension of salt (2) (0.965 g, 0.002 mmol) in acetonitrile (5 ml). The mixture immediately turned red, and the precipitate dissolved. The mixture was refluxed for 3 h. After cooling to room temperature, the mixture was poured into water (30 ml). The product was extracted with CHCl3 (3 Т 30 ml), and the extract was dried over CaCl2. The solvent was evaporated and the product was purified by column chromatography (SiO2, benzene acetone, 15:1). Single crystals of (1) were formed from the mother solution after chromatography (yield 0.41 g, 43%; m.p. 466 469 K). Spectroscopic analysis: 1H NMR (DMSO d6, , p.p.m.): 12.96 + 12.91 (s + s, 1H, NH), 8.12 8.10 (m, 1H, Ar), 7.73 7.71 (m, 1H, Ar), 7.55 7.32 (m, 5H, Ar), 7.26 7.22 (m, 1H, Ar), 7.09 7.07 (m, 1H, Ar), 2.69 + 2.63 (s + s, 3H, CH3); MS, m/z (%): 329 (15), 328/330 (57/22) [M+], 327 (12), 295/297 (31/10), 158 (12), 137 (14), 123 (27), 105 (88), 86 (11), 77 (100), 51 (21). Analysis, found: C 61.85, H 4.00, N 8.32%; calculated for C17H13ClN2OS: C 62.10, H 3.99, N 8.52%.

Figure 2
A plot showing the N H N hydrogen bonded (dashed lines) chain.

Crystal data
C17H13ClN2OS Mr = 328.81 Monoclinic, P21 =c А a = 7.2814 (15) A А b = 23.650 (3) A А c = 9.752 (5) A  = 110.46 (3) А V = 1573.4 (9) A3 Z=4 Dx = 1.388 Mg m 3 Cu K radiation Cell parameters from 25 reflections = 32 35 = 3.41 mm 1 T = 293 (2) K Prism, colourless 0.1 Т 0.1 Т 0.1 mm

Data collection
Enraf Nonius CAD4 diffractometer Non profiled ! scans Absorption correction: none 3236 measured reflections 3236 independent reflections 1639 reflections with I > 2 (I) max = 74.9 h= 9!8 k = 0 ! 29 l = 0 ! 12 1 standard reflection frequency: 120 min intensity decay: 2%

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Refinement
Refinement on F R[F 2 > 2 (F 2)] = 0.048 wR(F 2) = 0.059 S = 0.86 3236 reflections 204 parameters
2

Table 2
H atoms treated by a mixture of independent and constrained refinement w = 1/[ 2(Fo2) + (0.0051P)2] where P = (Fo2 + 2Fc2)/3 (С/ )max = 0.001 А Сmax = 0.23 e A 3 А Сmin = 0.21 e A 3

А Hydrogen bond geometry (A, ).
D--HСССA N1--H1СССN3
i

D--H 0.86 (3)
1 2

HСССA 2.09 (3)
.

DСССA 2.952 (3)

D--HСС СA 172 (3)

Symmetry code: (i) x; y ? 3; z 2

Table 1

А Selected geometric parameters (A, ).
S1--C2 S1--C19 Cl1--C16 O1--C6 N1--C2 N1--C5 C2--N3 N3--C4 C4--C5 C4--C6 C5--C13 C6--C7 C2--S1--C19 C2--N1--C5 N3--C2--N1 N3--C2--S1 N1--C2--S1 C2--N3--C4 C5--C4--N3 C5--C4--C6 N3--C4--C6 C4--C5--N1 C4--C5--C13 N1--C5--C13 O1--C6--C4 O1--C6--C7 C4--C6--C7 C8--C7--C12 C8--C7--C6 1.735 1.776 1.749 1.221 1.367 1.379 1.324 1.390 1.378 1.477 1.465 1.482 (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) C7--C8 C7--C12 C8--C9 C9--C10 C10--C11 C11--C12 C13--C18 C13--C14 C14--C15 C15--C16 C16--C17 C17--C18 C12--C7--C6 C9--C8--C7 C10--C9--C8 C9--C10--C11 C10--C11--C12 C11--C12--C7 C18--C13--C14 C18--C13--C5 C14--C13--C5 C15--C14--C13 C16--C15--C14 C15--C16--C17 C15--C16--Cl1 C17--C16--Cl1 C18--C17--C16 C17--C18--C13 1.384 1.395 1.371 1.365 1.375 1.391 1.387 1.400 1.378 1.365 1.381 1.370 118.5 120.9 120.5 119.9 120.5 119.4 117.8 122.1 120.1 121.0 119.2 121.6 119.1 119.3 118.7 121.7 (3) (3) (3) (4) (4) (4) (3) (3) (3) (3) (3) (3)

The H atom involved in the hydrogen bond was found in a difference Fourier map and refined independently. H atoms bonded to C atoms were included in calculated positions and refined as riding А atoms, with calculated C H bond lengths in the range 0.93 0.97 A. For methyl H atoms, Uiso(H) 1.5Ueq(C), while for other H atoms, Uiso(H) 1.2Ueq(C). Data collection: CAD 4 EXPRESS (Enraf Nonius, 1994); cell refinement: CAD 4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP 3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: WinGX (Farrugia, 1999).

99.66 (14) 107.2 (2) 111.9 (3) 126.7 (2) 121.4 (2) 105.0 (2) 110.2 (2) 132.4 (3) 117.4 (2) 105.6 (2) 133.5 (3) 120.9 (2) 118.8 (3) 120.3 (3) 120.8 (2) 118.8 (3) 122.4 (3)

(3) (3) (3) (3) (3) (3) (3) (2) (3) (3) (3) (3) (2) (2) (3) (3)

The authors are indebted to the Russian Foundation for Basic Research for covering the licence fee for the use of the Cambridge Structural Database (Version 1.8; Allen, 2002).

References
Allen, F. H. (2002). Acta Cryst. B58, 380 388. Enraf Nonius (1994). CAD-4 EXPRESS. Version 5.1/1.2. Enraf Nonius, Delft, The Netherlands. Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837 838. Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany. Liebscher, J. & Hassoun, A. (1988). Synthesis, pp. 816 820. Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of ? Gottingen, Germany. Spek, A. L. (2003). J. Appl. Cryst. 36, 7 13.

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