2-Amino-5-chloro-1,3-benzoxazole

Lynch, D.E.

doi:10.1107/S1600536804021786

organic compounds

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ISSN: 2056-9890

Volume 60| Part 10| October 2004| Pages o1715-o1716

https://doi.org/10.1107/S1600536804021786

2-Amino-5-chloro-1,3-benzoxazole

Daniel E. Lynch ^a ^*

^aSchool of Science and the Environment, Coventry University, Coventry CV1 5FB, England
^*Correspondence e-mail: apx106@coventry.ac.uk

(Received 1 September 2004; accepted 3 September 2004; online 11 September 2004)

The structure of the title compound, C₇H₅ClN₂O, comprises a planar molecule that associates via N—H⋯N interactions to form R₂²(8) graph set hydrogen-bonded dimers, while N—H⋯Cl associations from the second 2-amino H atom create a two-dimensional hydrogen-bonding network containing C₂²(8) helical chains.

Comment

2-Amino-5-chloro-1,3-benzoxazole, or Zoxazolamine, (I), is a human metabolite and a centrally acting myorelaxant that was formerly used as an antispasmodic and uricosuric; current uses for the compound include as a tool for assessing hepatic cytochrome P-450 activity in rodents (The Merck Index, 2001 ). Chemically, (I) is a 2-aminooxazole derivative, the Cambridge Structural Database, version of April 2004 (Allen, 2002 ) lists 22 (in total) 2-aminooxazoles, 2-aminooxazolines, 2-aminooxadiazoles and 2-aminobenzoxazoles, four being co-crystals containing (I) (Lynch, Daly & Parsons, 2000 , Lynch, Singh & Parsons, 2000 ). The structure of (I), reported here, consists of a planar molecule (Fig. 1) that associates via N—H⋯N interactions, forming a R₂²(8) graph set (Etter, 1990 ) hydrogen-bonded dimer (Fig. 2). The second 2-amino N—H donates to an adjacent Cl atom, creating a two-dimensional hydrogen-bonding network that consists of C₂²(8) helical chains. Hydrogen-bonding associations are listed in Table 1. Molecules of (I) are slip-stacked in the b-axis direction, 3.36 (2) Å apart.

Figure 1
The molecular structure and atom-numbering scheme for (I

). Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
Packing diagram for (I

). Dotted lines represent hydrogen bonds. [Symmetry codes (i) −x, −y, −z; (ii) x − ½, ½ − y, z − ½.]

Experimental

The title compound was purchased from Aldrich Chemical Co. and recrystallized from ethanol.

Crystal data

C₇H₅ClN₂O
M_r = 168.58
Monoclinic, P2₁/n
a = 9.4403 (19) Å
b = 3.7390 (7) Å
c = 19.737 (4) Å
β = 101.67 (3)°
V = 682.2 (2) Å³
Z = 4
D_x = 1.641 Mg m⁻³
Mo Kα radiation
Cell parameters from 3789 reflections
θ = 2.9–27.5°
μ = 0.49 mm⁻¹
T = 120 (2) K
Plate, colourless
0.24 × 0.18 × 0.05 mm

Data collection

Bruker–Nonius KappaCCD area-detector diffractometer
φ and ω scans
Absorption correction: multi-scan (SORTAV; Blessing, 1995 ) T_min = 0.806, T_max = 0.978
4816 measured reflections
1526 independent reflections
1360 reflections with I > 2σ(I)
R_int = 0.032
θ_max = 27.5°
h = −12 → 12
k = −4 → 4
l = −22 → 25

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.029
wR(F²) = 0.084
S = 1.06
1526 reflections
100 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.0405P)² + 0.2976P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.30 e Å⁻³

Table 1
Hydrogen-bonding geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N21—H21⋯N3ⁱ	0.88	2.04	2.901 (2)	166
N21—H22⋯Cl5ⁱⁱ	0.88	2.83	3.444 (2)	128
Symmetry codes: (i) -x,-y,-z; (ii) $[x-{\script{1\over 2}},{\script{1\over 2}}-y,z-{\script{1\over 2}}]$ .

All H atoms were included in the refinement at calculated positions, in the riding-model approximation, with aromatic C—H distances of 0.95 Å and N—H distances of 0.88 Å. The isotropic displacement parameters were set equal to 1.25U_eq of the carrier atom.

Data collection: DENZO (Otwinowski & Minor, 1997 ) and COLLECT (Hooft, 1998 ); cell refinement: DENZO and COLLECT; data reduction: DENZO, SCALEPACK (Otwinowski & Minor, 1997) and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON97 (Spek, 2003 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536804021786/rz6001sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536804021786/rz6001Isup2.hkl

Computing details top

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); cell refinement: DENZO and COLLECT; data reduction: DENZO, SCALEPACK (Otwinowski & Minor, 1997) and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON97 (Spek, 2003); software used to prepare material for publication: SHELXL97.

2-Amino-5-chloro-1,3-benzoxazole top

Crystal data top

C₇H₅ClN₂O	F(000) = 344
M_r = 168.58	D_x = 1.641 Mg m⁻³
Monoclinic, P2₁/n	Melting point = 458–458.5 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 9.4403 (19) Å	Cell parameters from 3789 reflections
b = 3.7390 (7) Å	θ = 2.9–27.5°
c = 19.737 (4) Å	µ = 0.49 mm⁻¹
β = 101.67 (3)°	T = 120 K
V = 682.2 (2) Å³	Plate, colourless
Z = 4	0.24 × 0.18 × 0.05 mm

Data collection top

Bruker–Nonius KappaCCD area-detector diffractometer	1526 independent reflections
Radiation source: Bruker–Nonius FR591 rotating anode	1360 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.032
Detector resolution: 9.091 pixels mm^-1	θ_max = 27.5°, θ_min = 3.5°
φ and ω scans	h = −12→12
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	k = −4→4
T_min = 0.806, T_max = 0.978	l = −22→25
4816 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.084	H-atom parameters constrained
S = 1.06	w = 1/[σ²(F_o²) + (0.0405P)² + 0.2976P] where P = (F_o² + 2F_c²)/3
1526 reflections	(Δ/σ)_max < 0.001
100 parameters	Δρ_max = 0.31 e Å⁻³
0 restraints	Δρ_min = −0.30 e Å⁻³

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.35183 (11)	0.2435 (3)	0.01453 (5)	0.0168 (2)
C2	0.21001 (15)	0.1379 (4)	0.00663 (7)	0.0168 (3)
N21	0.12672 (14)	0.1887 (4)	−0.05575 (6)	0.0234 (3)
H21	0.0359	0.1183	−0.0641	0.029*
H22	0.1626	0.2926	−0.0886	0.029*
N3	0.17429 (12)	−0.0105 (3)	0.06061 (6)	0.0165 (3)
C4	0.33211 (14)	−0.1232 (4)	0.17882 (7)	0.0146 (3)
H4	0.2601	−0.2295	0.1997	0.018*
C5	0.47302 (15)	−0.0765 (4)	0.21461 (7)	0.0148 (3)
Cl5	0.51663 (4)	−0.21998 (9)	0.300743 (16)	0.01855 (14)
C6	0.58231 (15)	0.0731 (4)	0.18576 (7)	0.0163 (3)
H6	0.6775	0.0948	0.2127	0.020*
C7	0.55165 (15)	0.1915 (4)	0.11709 (8)	0.0167 (3)
H7	0.6235	0.2957	0.0959	0.021*
C8	0.41178 (15)	0.1480 (4)	0.08232 (7)	0.0147 (3)
C9	0.30223 (14)	−0.0054 (4)	0.11057 (7)	0.0137 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0157 (5)	0.0231 (6)	0.0112 (5)	−0.0035 (4)	0.0015 (4)	0.0023 (4)
C2	0.0164 (7)	0.0184 (7)	0.0149 (7)	−0.0024 (6)	0.0015 (5)	−0.0012 (5)
N21	0.0190 (7)	0.0374 (8)	0.0123 (6)	−0.0066 (5)	−0.0008 (5)	0.0067 (5)
N3	0.0158 (6)	0.0203 (6)	0.0123 (5)	−0.0015 (5)	0.0001 (4)	0.0014 (5)
C4	0.0159 (7)	0.0140 (7)	0.0142 (7)	0.0004 (5)	0.0038 (5)	−0.0002 (5)
C5	0.0190 (7)	0.0126 (7)	0.0121 (6)	0.0012 (5)	0.0012 (5)	−0.0010 (5)
Cl5	0.0210 (2)	0.0211 (2)	0.0118 (2)	0.00004 (13)	−0.00093 (15)	0.00199 (12)
C6	0.0147 (7)	0.0161 (7)	0.0166 (6)	−0.0005 (5)	−0.0001 (5)	−0.0017 (5)
C7	0.0161 (7)	0.0173 (7)	0.0172 (7)	−0.0026 (5)	0.0045 (6)	−0.0015 (5)
C8	0.0184 (7)	0.0151 (7)	0.0102 (6)	0.0000 (6)	0.0023 (5)	−0.0004 (5)
C9	0.0139 (6)	0.0131 (7)	0.0137 (6)	−0.0003 (5)	0.0017 (5)	−0.0021 (5)

Geometric parameters (Å, º) top

O1—C2	1.3742 (17)	C4—H4	0.95
O1—C8	1.3898 (17)	C5—C6	1.3926 (19)
C2—N3	1.3045 (18)	C5—Cl5	1.7504 (14)
C2—N21	1.3335 (19)	C6—C7	1.399 (2)
N21—H21	0.88	C6—H6	0.95
N21—H22	0.88	C7—C8	1.369 (2)
N3—C9	1.3962 (18)	C7—H7	0.95
C4—C5	1.385 (2)	C8—C9	1.3937 (19)
C4—C9	1.3908 (19)

C2—O1—C8	103.47 (11)	C6—C5—Cl5	118.17 (11)
N3—C2—N21	127.81 (13)	C5—C6—C7	119.86 (13)
N3—C2—O1	115.88 (13)	C5—C6—H6	120.1
N21—C2—O1	116.28 (12)	C7—C6—H6	120.1
C2—N21—H21	120.0	C8—C7—C6	115.94 (13)
C2—N21—H22	120.0	C8—C7—H7	122.0
H21—N21—H22	120.0	C6—C7—H7	122.0
C2—N3—C9	103.97 (11)	C7—C8—O1	127.99 (12)
C5—C4—C9	116.09 (12)	C7—C8—C9	124.53 (13)
C5—C4—H4	122.0	O1—C8—C9	107.47 (12)
C9—C4—H4	122.0	C4—C9—C8	119.75 (13)
C4—C5—C6	123.82 (13)	C4—C9—N3	131.05 (12)
C4—C5—Cl5	118.01 (10)	C8—C9—N3	109.21 (12)

C8—O1—C2—N3	−0.01 (16)	C2—O1—C8—C7	179.64 (14)
C8—O1—C2—N21	−177.95 (13)	C2—O1—C8—C9	−0.43 (14)
N21—C2—N3—C9	178.10 (15)	C5—C4—C9—C8	0.2 (2)
O1—C2—N3—C9	0.43 (16)	C5—C4—C9—N3	−179.91 (13)
C9—C4—C5—C6	−1.0 (2)	C7—C8—C9—C4	0.6 (2)
C9—C4—C5—Cl5	179.99 (10)	O1—C8—C9—C4	−179.34 (11)
C4—C5—C6—C7	1.0 (2)	C7—C8—C9—N3	−179.36 (13)
Cl5—C5—C6—C7	−179.90 (11)	O1—C8—C9—N3	0.71 (15)
C5—C6—C7—C8	−0.3 (2)	C2—N3—C9—C4	179.37 (14)
C6—C7—C8—O1	179.40 (13)	C2—N3—C9—C8	−0.68 (15)
C6—C7—C8—C9	−0.5 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N21—H21···N3ⁱ	0.88	2.04	2.901 (2)	166
N21—H22···Cl5ⁱⁱ	0.88	2.83	3.444 (2)	128

Symmetry codes: (i) −x, −y, −z; (ii) x−1/2, −y+1/2, z−1/2.

Acknowledgements

The author thanks the EPSRC National Crystallography Service (Southampton, England) and the EPSRC Chemical Database Service at Daresbury.

References

Allen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
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Etter, M. C. (1990). Acc. Chem. Res. 23, 120–126. CrossRef CAS Web of Science Google Scholar
Hooft, R. W. W. (1998). COLLECT. Nonius BV, Delft, The Netherlands. Google Scholar
Lynch, D. E., Daly, D. & Parsons, S. (2000). Acta Cryst. C56, 1478–1479. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Lynch, D. E., Singh, M. & Parsons, S. (2000). Cryst. Eng. 3, 71–79. CSD CrossRef CAS Google Scholar
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr and R. M. Sweet, pp. 307–326. New York: Academic Press. Google Scholar
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany. Google Scholar
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CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 60| Part 10| October 2004| Pages o1715-o1716

https://doi.org/10.1107/S1600536804021786

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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

2-Amino-5-chloro-1,3-benzoxazole

Comment

Experimental

Crystal data

Data collection

Refinement

Supporting information

Acknowledgements

References

organic compounds