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

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ISSN: 2056-9890

6-Meth­­oxy-1,3-benzo­thia­zol-2-amine

aDepartment of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan, and bDepartment Chemie, Fakultät fur Naturwissenschaften, Universität Paderborn, Warburgerstrasse 100, D-33098 Paderborn, Germany.
*Correspondence e-mail: aamersaeed@yahoo.com

(Received 13 June 2012; accepted 21 June 2012; online 30 June 2012)

The title compound, C8H8N2OS, is almost planar, the C—C—O—C torsion angle associated with the meth­oxy group being 0.72 (1)°. Inter­molecular amine N—H⋯N hydrogen-bonding inter­actions form inversion dimers [graph set R22(8)] which are extended into chains along the b axis through amine N—H⋯O hydrogen bonds.

Related literature

For information on various important biological activities of amino­benzothia­zoles, see: Hutchinson et al. (2002[Hutchinson, I., Jennings, S. A., Vishnuvajjala, B. R., Westwell, A. D. & Stevens, M. F. G. (2002). J. Med. Chem. 45, 744-747.]); Benavides et al. (1985[Benavides, J., Camelin, J. C., Mitrani, N., Flamand, F., Uzan, A., Legrand, J. J., Guereny, C. & LeFur, G. (1985). Neuropharmacology, 24, 1085-1089.]); La'cova et al. (1991[La'cova, M., Chovancova, J., Hyblova, O. & Varkonda, S. (1991). Chem. Pap. Chem. Zvesti, 45, 411-414.]). For their pharmaceutical applications, see: Suter & Zutter (1967[Suter, H. & Zutter, H. (1967). Helv. Chim. Acta, 50, 1084-1090.]); Sawhney et al. (1978[Sawhney, S. N., Arora, S. K., Singh, J. V., Bansal, O. P. & Singh, S. P. (1978). Indian J. Chem. Sect. B, 16, 605-609.]); Bensimon et al. (1994[Bensimon, G., Lacomblez, L. & Meininger, V. (1994). N. Engl. J. Med. 330, 585-589.]); Foscolos et al. (1977[Foscolos, G., Tsatsas, G., Champagnac, A. & Pommier, M. (1977). Ann. Pharm. Fr. 35, 295-297.]); Shirke et al. (1990[Shirke, V. G., Bobade, K., Bhamaria, R. P., Khadse, B. G. & Sengupta, S. R. (1990). Indian Drugs, 27, 350-354.]); Paget et al. (1969[Paget, C. J., Kisner, K., Stone, R. L. & DeLong, D. C. (1969). J. Med. Chem. 12, 1016-1018.]); Domino et al. (1952[Domino, E. F., Unna, K. R. & Kerwin, J. (1952). J. Pharmacol. Exp. Ther. 105, 486-490.]). For anti­microbial and pesticidal activities, see: Pattan et al. (2002[Pattan, S. R., Babu, S. N. N. & Angadi, J. (2002). Indian J. Heterocycl. Chem. 11, 333-337.]); Kaufmann (1935[Kaufmann, H. P. (1935). Arch. Pharm. 273, 22-26.]). For related structures see: Saeed et al. (2007[Saeed, A., Rafique, H. & Bolte, M. (2007). Acta Cryst. E63, o4247.]); Sun et al. (2011[Sun, D., Li, Y.-H., Hao, H.-J., Liu, F.-J., Wen, Y.-M., Huang, R.-B. & Zheng, L.-S. (2011). Cryst. Growth Des. 11, 3323-3327.]). For graph-set analysis, see: Etter et al. (1990[Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256-262.]).

[Scheme 1]

Experimental

Crystal data
  • C8H8N2OS

  • Mr = 180.23

  • Orthorhombic, P b c a

  • a = 15.060 (2) Å

  • b = 6.6997 (11) Å

  • c = 16.649 (3) Å

  • V = 1679.8 (5) Å3

  • Z = 8

  • Mo Kα radiation

  • μ = 0.33 mm−1

  • T = 130 K

  • 0.47 × 0.23 × 0.14 mm

Data collection
  • Bruker SMART APEX CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 2004[Sheldrick, G. M. (2004). SADABS. University of Göttingen, Germany.]) Tmin = 0.859, Tmax = 0.955

  • 14745 measured reflections

  • 2010 independent reflections

  • 1771 reflections with I > 2σ(I)

  • Rint = 0.029

Refinement
  • R[F2 > 2σ(F2)] = 0.033

  • wR(F2) = 0.094

  • S = 1.06

  • 2010 reflections

  • 110 parameters

  • H-atom parameters constrained

  • Δρmax = 0.40 e Å−3

  • Δρmin = −0.20 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N2—H2A⋯N1i 0.88 2.13 2.9774 (16) 163
N2—H2B⋯O1ii 0.88 2.10 2.9655 (16) 170
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) [x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}].

Data collection: SMART (Bruker, 2002[Bruker (2002). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2002[Bruker (2002). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL and local programs.

Supporting information


Comment top

2-Aminobenzothiazoles display a broad spectrum of important pharmaceutical applications and a number of derivatives are therapeutic agents for the treatment of various diseases e.g. diabetes (Suter & Zutter, 1967); inflammation (Sawhney et al., 1978); amyotrophic lateral sclerosis (Bensimon et al., 1994); analgesia (Foscolos et al., 1977); tuberculosis (Shirke et al. 1990); viral infections (Paget et al., 1969), and as central muscle relaxants (Domino et al., 1952). Riluzole [6-(trifluoromethoxy)-2-benzothiazolamine] possesses potent anticonvulsant and neuroprotective effects (Benavides et al., 1985). 6-Nitro or 6-amino 2-substituted benzothiazoles and fluorobenzothiazoles possess significant antimicrobial activity (Pattan et al., 2002) and 6-ethoxy-2-amino benzothiazole is a strong local anesthetic agent (La'cova et al., 1991).

The title compound, C8H8N2OS, is almost planar (Fig. 1) with the C4—C5—O1—C8 torsion angle associated with the methoxy group = 0.72 (1)° and the amine hydrogen atoms lying in the molecular plane. Intermolecular amine N—H···N hydrogen-bonding interactions (Table 1) form centrosymmetric cyclic dimers [graph set R22(8): Etter et al., 1990] which are extended into one-dimensional chains along the b axis, through amine N—H···O hydrogen bonds (Fig. 2).

Related literature top

For information on various important biological activities of aminobenzothiazoles, see: Hutchinson et al. (2002); Benavides et al. (1985); La'cova et al. (1991). For their pharmaceutical applications, see: Suter & Zutter (1967); Sawhney et al. (1978); Bensimon et al. (1994); Foscolos et al. (1977); Shirke et al. (1990); Paget et al. (1969); Domino et al. (1952). For antimicrobial and pesticidal activities, see: Pattan et al. (2002); Kaufmann (1935). For related structures see: Saeed et al. (2007); Sun et al. (2011). For graph-set analysis, see: Etter et al. (1990).

Experimental top

A mixture of p-anisidine (3.7 g, 0.03 mol) and potassium thiocyanate (11.6 g, 0.12 mol) in AcOH (45 ml) was stirred at 20 °C for 10 minutes. A solution of bromine (1.5 ml, 0.03 mol) in AcOH (20 ml) was added over 20 min and the reaction mixture was stirred for 21 h at room temperature. The reaction mixture was poured into cold NH4OH (90 ml) and extracted with EtOAc. The organic phase was washed with water, dried, filtered and evaporated. The crude product obtained was recrystallized using ethanol as solvent. Yield = 83%; m.p. = 145-147 °C; IR (KBr) 3389 (NH), 2733 (C-S), 1644 (C=N), 1585 (C=C), 1442 (C-N) cm-1; 1H NMR (CDCl3, ? p.p.m.): 7.47 (1H, d, J = 8.7 Hz, H-1), 7.14 (1H, d, J = 2.4 Hz, H-2), 6.93 (1H, dd, J = 8.7,2.4 Hz, H-3), 5.41 (1H, bs, -NH), 3.81 (3H, s, -OCH3); 13 C NMR (CDCl3, ppm): 166.2 (S-C=N), 145.1 (C-9), 138.6 (C-6), 126.5 (C-8), 124.6 (C-4), 121.4 (C-5), 116.5 (C-7), 56.8 (-OCH3); EIMS (70 eV): m/z (%); [M+.] 180 (51%); Anal. Calcd. for C8H8N2OS; C, 52.33; H, 4.44; N, 15.55; S, 17.77. Found: C, 52.26; H, 4.35; N, 15.37; S, 17.61..

Refinement top

Hydrogen atoms were clearly identified in difference syntheses, and were refined at idealized positions [C—N = 0.88 Å; C—H(aromatic) = 0.93 Å and C—H(methyl) = 0.96 Å], riding on the nitrogen or carbon atoms with isotropic displacement parameters Uiso(H) = 1.2Ueq(N, Car) or 1.5Ueq(Cmethyl). The hydrogen atoms were allowed to rotate but not to tip.

Computing details top

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and local programs.

Figures top
Fig. 1. Molecular structure of title compound showing atom numbering scheme and displacement ellipsoids drawn at the 50% probability level.

Fig. 2. Crystal packing viewed along (010) with intermolecular hydrogen bonds indicated as dashed lines. H-atoms not involved in hydrogen bonding are omitted.
6-Methoxy-1,3-benzothiazol-2-amine top
Crystal data top
C8H8N2OSDx = 1.425 Mg m3
Mr = 180.23Melting point = 418–420 K
Orthorhombic, PbcaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2abCell parameters from 3739 reflections
a = 15.060 (2) Åθ = 2.5–28.3°
b = 6.6997 (11) ŵ = 0.33 mm1
c = 16.649 (3) ÅT = 130 K
V = 1679.8 (5) Å3Prism, colourless
Z = 80.47 × 0.23 × 0.14 mm
F(000) = 752
Data collection top
Bruker SMART APEX CCD
diffractometer
2010 independent reflections
Radiation source: sealed tube1771 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.029
ϕ and ω scansθmax = 27.9°, θmin = 2.5°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2004)
h = 1919
Tmin = 0.859, Tmax = 0.955k = 88
14745 measured reflectionsl = 2120
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.033Hydrogen site location: difference Fourier map
wR(F2) = 0.094H-atom parameters constrained
S = 1.06 w = 1/[σ2(Fo2) + (0.0541P)2 + 0.5583P]
where P = (Fo2 + 2Fc2)/3
2010 reflections(Δ/σ)max = 0.001
110 parametersΔρmax = 0.40 e Å3
0 restraintsΔρmin = 0.20 e Å3
Crystal data top
C8H8N2OSV = 1679.8 (5) Å3
Mr = 180.23Z = 8
Orthorhombic, PbcaMo Kα radiation
a = 15.060 (2) ŵ = 0.33 mm1
b = 6.6997 (11) ÅT = 130 K
c = 16.649 (3) Å0.47 × 0.23 × 0.14 mm
Data collection top
Bruker SMART APEX CCD
diffractometer
2010 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2004)
1771 reflections with I > 2σ(I)
Tmin = 0.859, Tmax = 0.955Rint = 0.029
14745 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0330 restraints
wR(F2) = 0.094H-atom parameters constrained
S = 1.06Δρmax = 0.40 e Å3
2010 reflectionsΔρmin = 0.20 e Å3
110 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
S10.67080 (2)0.21698 (5)0.37026 (2)0.02447 (13)
O10.68079 (6)0.55013 (14)0.09070 (6)0.0234 (2)
N10.56180 (7)0.50795 (17)0.40573 (6)0.0217 (2)
N20.58824 (8)0.28778 (19)0.51177 (7)0.0292 (3)
H2A0.55250.35360.54420.035*
H2B0.61600.18050.52900.035*
C10.60027 (9)0.3510 (2)0.43608 (8)0.0220 (3)
C20.58749 (8)0.53507 (19)0.32593 (8)0.0191 (3)
C30.56017 (9)0.6894 (2)0.27627 (8)0.0225 (3)
H3A0.52110.78920.29620.027*
C40.58993 (9)0.6982 (2)0.19719 (8)0.0220 (3)
H4A0.57100.80360.16300.026*
C50.64762 (8)0.55186 (19)0.16817 (8)0.0193 (3)
C60.67681 (8)0.3964 (2)0.21681 (8)0.0209 (3)
H6A0.71620.29730.19680.025*
C70.64648 (8)0.39071 (19)0.29540 (8)0.0193 (3)
C80.65274 (10)0.7074 (2)0.03804 (9)0.0281 (3)
H8A0.58780.70680.03400.042*
H8B0.67860.68670.01530.042*
H8C0.67260.83600.05950.042*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0272 (2)0.0253 (2)0.0208 (2)0.00985 (13)0.00107 (13)0.00191 (12)
O10.0249 (5)0.0256 (5)0.0195 (5)0.0008 (4)0.0041 (4)0.0015 (4)
N10.0242 (5)0.0232 (5)0.0177 (5)0.0041 (4)0.0009 (4)0.0017 (4)
N20.0358 (7)0.0314 (7)0.0203 (6)0.0133 (5)0.0027 (5)0.0039 (5)
C10.0220 (6)0.0253 (7)0.0187 (6)0.0030 (5)0.0011 (5)0.0028 (5)
C20.0178 (6)0.0215 (6)0.0180 (6)0.0010 (5)0.0013 (5)0.0027 (5)
C30.0230 (6)0.0224 (6)0.0223 (6)0.0058 (5)0.0005 (5)0.0014 (5)
C40.0220 (6)0.0220 (6)0.0220 (7)0.0020 (5)0.0016 (5)0.0017 (5)
C50.0177 (6)0.0222 (6)0.0181 (6)0.0034 (5)0.0012 (5)0.0020 (5)
C60.0182 (6)0.0217 (6)0.0229 (7)0.0026 (5)0.0010 (5)0.0027 (5)
C70.0182 (6)0.0196 (6)0.0202 (6)0.0018 (5)0.0027 (5)0.0012 (5)
C80.0339 (8)0.0290 (8)0.0213 (7)0.0006 (6)0.0037 (6)0.0052 (6)
Geometric parameters (Å, º) top
S1—C71.7443 (13)C3—C41.3920 (19)
S1—C11.7705 (14)C3—H3A0.9500
O1—C51.3832 (16)C4—C51.3962 (18)
O1—C81.4342 (17)C4—H4A0.9500
N1—C11.3028 (18)C5—C61.3908 (18)
N1—C21.3956 (17)C6—C71.3864 (18)
N2—C11.3417 (18)C6—H6A0.9500
N2—H2A0.8800C8—H8A0.9800
N2—H2B0.8800C8—H8B0.9800
C2—C31.3864 (18)C8—H8C0.9800
C2—C71.4083 (18)
C7—S1—C188.73 (6)C5—C4—H4A120.1
C5—O1—C8117.23 (10)O1—C5—C6114.99 (11)
C1—N1—C2110.55 (11)O1—C5—C4123.59 (12)
C1—N2—H2A120.0C6—C5—C4121.42 (12)
C1—N2—H2B120.0C7—C6—C5117.76 (12)
H2A—N2—H2B120.0C7—C6—H6A121.1
N1—C1—N2123.98 (13)C5—C6—H6A121.1
N1—C1—S1115.86 (10)C6—C7—C2121.99 (12)
N2—C1—S1120.15 (11)C6—C7—S1128.57 (10)
C3—C2—N1125.63 (12)C2—C7—S1109.44 (10)
C3—C2—C7118.96 (12)O1—C8—H8A109.5
N1—C2—C7115.41 (11)O1—C8—H8B109.5
C2—C3—C4120.01 (12)H8A—C8—H8B109.5
C2—C3—H3A120.0O1—C8—H8C109.5
C4—C3—H3A120.0H8A—C8—H8C109.5
C3—C4—C5119.86 (12)H8B—C8—H8C109.5
C3—C4—H4A120.1
C2—N1—C1—N2179.99 (13)C3—C4—C5—C60.3 (2)
C2—N1—C1—S10.87 (15)O1—C5—C6—C7179.48 (11)
C7—S1—C1—N10.50 (11)C4—C5—C6—C70.19 (19)
C7—S1—C1—N2179.67 (12)C5—C6—C7—C20.6 (2)
C1—N1—C2—C3178.88 (13)C5—C6—C7—S1179.95 (10)
C1—N1—C2—C70.90 (17)C3—C2—C7—C61.2 (2)
N1—C2—C3—C4179.23 (12)N1—C2—C7—C6179.05 (12)
C7—C2—C3—C41.0 (2)C3—C2—C7—S1179.27 (10)
C2—C3—C4—C50.3 (2)N1—C2—C7—S10.53 (15)
C8—O1—C5—C6180.00 (11)C1—S1—C7—C6179.51 (13)
C8—O1—C5—C40.72 (18)C1—S1—C7—C20.04 (10)
C3—C4—C5—O1179.55 (12)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···N1i0.882.132.9774 (16)163
N2—H2B···O1ii0.882.102.9655 (16)170
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC8H8N2OS
Mr180.23
Crystal system, space groupOrthorhombic, Pbca
Temperature (K)130
a, b, c (Å)15.060 (2), 6.6997 (11), 16.649 (3)
V3)1679.8 (5)
Z8
Radiation typeMo Kα
µ (mm1)0.33
Crystal size (mm)0.47 × 0.23 × 0.14
Data collection
DiffractometerBruker SMART APEX CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2004)
Tmin, Tmax0.859, 0.955
No. of measured, independent and
observed [I > 2σ(I)] reflections
14745, 2010, 1771
Rint0.029
(sin θ/λ)max1)0.658
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.033, 0.094, 1.06
No. of reflections2010
No. of parameters110
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.40, 0.20

Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and local programs.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···N1i0.882.132.9774 (16)162.5
N2—H2B···O1ii0.882.102.9655 (16)169.6
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y+1/2, z+1/2.
 

Acknowledgements

AS gratefully acknowledges a research grant from the Higher Education Commission of Pakistan under the project No. 4-279/PAK-US/HEC 2010-917 (Pakistan–US Science and Technology Cooperation Program).

References

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