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organic papers
Acta Crystallographica Section E

Structure Reports Online
ISSN 1600-5368

5-(4-Bromophenyl)-1,3-oxazol-2-amine

Victor B. Rybakov,* Vadim L. Alifanov and Eugene V. Babaev
Department of Chemistry, Moscow State University, 119992 Moscow, Russian Federation Correspondence e-mail: rybakov20021@yandex.ru

The title compound, C9H7BrN2O, was synthesized by the hydrazinolysis of 2-(4-bromophenyl)oxazolo[3,2-a]pyrimidinium perchlorate. In the molecule, the oxazole and benzene rings make a dihedral angle of 9.68 (7) . The crystal packing is stabilized by intermolecular N HСССN hydrogen bonds and van der Waals forces.

Received 15 September 2006 Accepted 22 September 2006

Comment
In our previous communication (Rybakov et al., 2006) we have reported the synthesis and crystal structure of 2-(4-bromophenyl)oxazolo[3,2-a]pyrimidinium perchlorate, (1). Investigating the reaction of (1) with hydrazine we have found that the cation of (1) underwent selective cleavage of the pyrimidine fragment resulting in the title compound, (2). This type of conversion, unknown in the literature, provides an efficient method of synthesis of 2-aminooxazoles. The title compound, (2), was obtained in 96% yield, which is much better than the known synthetic routes, where (2) has been synthesized either by the reaction of cyanourea with p-bromophenacyl bromide (Beiling et al., 1965; Beyer & Schilling, 1966; van Leusen et al., 1981) or by the Curtius rearrangement of the hydrazide of oxazolyl-2-carboxylic acid (Tanaka & Nishiki, 1967). We report here the crystal structure of (2).

Key indicators Single-crystal X-ray study T = 293 K А Mean (C-C) = 0.002 A R factor = 0.049 wR factor = 0.091 Data-to-parameter ratio = 14.6 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

In (2) (Fig. 1), all bonds lengths and angles show normal values (Allen et al., 1987). The oxazole and benzene rings make a dihedral angle of 9.68 (7) . There is one exocyclic C N bond involving an amino group (N5). Although amino imino tautomerism is possible for -aminoheterocycles, X-ray data confirm the amino form in (2). A search for this amino group in 2-aminooxazoles collected in the Cambridge Structural Database (Version 5.27; Allen, 2002) resulted in only four hits only: 2-amino-6-ethyl-4,5,7,8-tetrahydro-6H-oxazolo(5,4-d)azepine (Carpy et al., 1982), 6-allyl-2-amino-5,6,7,8tetrahydro-4H-oxazolo(5,4-d)azepine (Luger et al., 1986), ethyl-2-amino-oxazole-5-carboxylate (Kennedy et al., 2001) and 2-amino-4,5-dimethyl-3-(ethoxycarbonylmethyl)-1,3oxazolium bromide (Peters et al., 1999). The mean exocyclic А C N bond length for these hits is 1.327 (17) A, while in (2) А. C5 N5 is 1.2910 (18) A The crystal packing (Fig. 2) is stabilized by intermolecular N HСССN hydrogen bonds (Table 1), which link the molecules into centrosymmetric dimers, and van der Waals forces.
doi:10.1107/S1600536806038918 Acta Cryst. (2006). E62, o4746 o4747

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organic papers

Figure 1
The molecular structure of the title compound, showing the atom numbering scheme and displacement ellipsoids at the 50% probability level.

Figure 2
The packing, showing the hydrogen bonds as dashed lines.

Experimental
Compound (1) (0.01 mol) was suspended in 50 ml of acetonitrile, and 5 ml of hydrazine hydrate was added with stirring. The reaction mixture was refluxed for 0.5 h, cooled to room temperature and poured into 200 ml of water. The product was isolated by suction and recrystallized from ethanol. Crystal data
C9H7BrN2O Mr = 239.07 Orthorhombic, Pccn А a = 39.344 (3) A А b = 7.5684 (8) A А c = 6.0571 (8) A А V = 1803.6 (3) A3 Z=8 Dx = 1.761 Mg m 3 Cu K radiation = 5.88 mm 1 T = 293 (2) K Plate, yellow 0.12 Т 0.12 Т 0.02 mm

The C bound H atoms were positioned geometrically (C H А 0.93 A) and refined as riding, with Uiso(H) 1.2Ueq(C). The amino H atoms H5A and H5B were initially placed in calculated positions, and then refined isotropically. 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 MERCURY (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 1999).

The authors are indebted to the Russian Foundation for Basic Research for covering the licence fee for use of the Cambridge Structural Database.

References
Allen, F. H. (2002). Acta Cryst. B58, 380 388. Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1 19. Beiling, H., Barth, P. & Beyer, H. (1965). Z. Chem. 5, 182 183. Beyer, H. & Schilling, H. (1966). Chem. Ber. 99, 2110 2117. Carpy, A., Leger, J.-M. & Colleter, J.-C. (1982). Cryst. Struct. Commun. 11, 53 55. Enraf Nonius (1994). CAD-4 Software. Version 5.0. 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. Kennedy, A. R., Khalaf, A. I., Suckling, C. J. & Waigh, R. D. (2001). Acta Cryst. E57, o832 o833. Leusen, A. van, Jeuring, H. & Widelmann, J. (1981). J. Org. Chem. 46, 2069 2072. Luger, P., Griss, G., Hurnaus, R. & Trummlitz, G. (1986). Acta Cryst. B42, 478 490. Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453 457. North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351 359. Peters, K., Peters, E.-M., Ventzke, B. & Hetzheim, A. (1999). Z. Kristallogr. New Cryst. Struct. 214, 353 354. Rybakov, V. B., Alifanov, V. L. & Babaev, E. V. (2006). Acta Cryst. E62, o4578 o4580. Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of ? Gottingen, Germany. Tanaka, C. & Nishiki, H. (1967). Yakugaku Zasshi, 87, 10 21 (in Japanese); Chem. Abstr. 1967, 94930.

Data collection
Enraf Nonius CAD-4 diffractometer ! scans Absorption correction: scan (North et al., 1968) Tmin = 0.539, Tmax = 0.891 1860 measured reflections 1860 independent reflections 1644 reflections with I > 2 (I) max = 75.0 1 standard reflection frequency: 60 min intensity decay: 3%

Refinement
Refinement on F 2 R[F 2 > 2 (F 2)] = 0.049 wR(F 2) = 0.091 S = 1.03 1860 reflections 127 parameters H atoms treated by a mixture of independent and constrained refinement w = 1/[ 2(Fo2) + (0.0753P)2] where P = (Fo2 + 2Fc2)/3 (С/ )max = 0.001 А Сmax = 0.56 e A 3 А Сmin = 0.78 e A 3 Extinction correction: SHELXL97 Extinction coefficient: 0.0021 (2)

Table 1

А Hydrogen bond geometry (A, ).
D--HСССA N5--H5AСС СN1
i

D--H 0.84 (3)

HСС СA 2.12 (3)

DСС СA 2.947 (2)

D--HСС СA 165 (3)

Symmetry code: (i)

x ? 1; y ? 2; z ? 2.

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