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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 66| Part 4| April 2010| Pages o773-o774

2-[(E)-(3,4-Di­methyl­isoxazol-5-yl)imino­meth­yl]phenol

aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and bDepartment of Chemistry, Faculty of Science, King Abdu Aziz University, Jeddah, Saudi Arabia
*Correspondence e-mail: hkfun@usm.my

(Received 24 February 2010; accepted 3 March 2010; online 6 March 2010)

The title compound, C12H12N2O2, has been synthesized by the reaction of 5-amino-3,4-dimethyl­isoxazole and salicyladehyde. The mol­ecule adopts an E configuration about the central C=N double bond. The dihedral angle between the isoxazole and phenyl rings is 4.2 (2)° and an intra­molecular O—H⋯N hydrogen bond generates an S(6) ring motif. The crystal studied was a non-merohedral twin with a domain ratio of 0.834 (4):0.166 (4).

Related literature

For background to the biological and pharmacological properties of oxazole derivatives, see: Spinelli (1999[Spinelli, O. A. (1999). Ital. Soc. Chem. 3 301-339.]); Conti et al. (1998[Conti, P., Dallanoce, C., Amici, M. D., Micheli, C. D. & Klotz, K. N. (1998). Bioorg. Med. Chem. 6, 401-409.]); Mishra et al. (1998[Mishra, A., Jain, K. J. & Asthana, J. G. (1998). Oriental J. Chem. 14, 151-152.]); Ko et al. (1998[Ko, D. H., Maponya, M. F., Khalil, M. A., Oriaku, E. T. & You, Z. (1998). J. Med. Chem. Res. 8, 313-318.]); Kang et al. (2000[Kang, Y. Y., Shin, K. L., Yoo, K. H., Seo, K. J., Hong, C. Y., Lee, C. S., Park, S. Y., Kim, D. J. & Park, S. W. (2000). Bioorg. Med. Chem. Lett. 10, 95-99.]); Huang & Chen (2005[Huang, L. & Chen, D.-B. (2005). Acta Cryst. E61, o4169-o4170.]). For details of hydrogen bonding and hydrogen-bond motifs, see: Jeffrey & Saenger (1991[Jeffrey, G. A. & Saenger, W. (1991). Hydrogen Bonding in Biological Structures. Berlin: Springer.]); Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]); Jeffrey (1997[Jeffrey, G. A. (1997). An Introduction to Hydrogen Bonding. Oxford University Press.]); Scheiner (1997[Scheiner, S. (1997). Hydrogen Bonding, A Theoretical Perspective. Oxford University Press.]). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986[Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105-107.]).

[Scheme 1]

Experimental

Crystal data
  • C12H12N2O2

  • Mr = 216.24

  • Triclinic, [P \overline 1]

  • a = 5.3475 (14) Å

  • b = 8.615 (2) Å

  • c = 12.321 (3) Å

  • α = 103.696 (5)°

  • β = 91.486 (5)°

  • γ = 94.059 (5)°

  • V = 549.6 (2) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.09 mm−1

  • T = 100 K

  • 0.56 × 0.14 × 0.08 mm

Data collection
  • Bruker APEX DUO CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.951, Tmax = 0.993

  • 2467 measured reflections

  • 2467 independent reflections

  • 1946 reflections with I > 2σ(I)

Refinement
  • R[F2 > 2σ(F2)] = 0.070

  • wR(F2) = 0.203

  • S = 1.06

  • 2467 reflections

  • 152 parameters

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.40 e Å−3

  • Δρmin = −0.34 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O2—H1O2⋯N1 1.00 (9) 1.71 (8) 2.648 (5) 154 (8)

Data collection: APEX2 (Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]).

Supporting information


Comment top

Heterocyclic compounds, especially isoxazoles, are one of the key building elements of natural products. Among the numerous heterocyclic systems of biological and pharmacological interest, the oxazole ring is endowed with various activities, including hypoglycemic (Spinelli, 1999), analgesic (Conti et al., 1998), anti-inflammatory (Mishra et al., 1998), anti-bacterial (Ko et al., 1998) and anti-tumor (Kang et al., 2000) properties. In view of the importance of the title compound as a pharmaceutical intermediate, the paper reports its synthesis and crystal structure.

In the title compound (Fig. 1), the isoxazole ring is essentially planar with a maximum deviation of 0.002 (2) Å for atom C8. The dihedral angle between the isoxazole ring (N2/O1/C8–C10) and the phenyl ring (C1–C6) is 4.30 (15)°. The methyl groups at C9 and C10 deviate from the isoxazole mean plane by 0.056 (3) Å and 0.013 (4) Å , respectively. The C5—O2 and C7N1 bond lengths are 1.353 (4) Å and 1.293 (4) Å, respectively, and agree with the corresponding values in 4-{[(1E)-(3,5-dibromo-2-hydroxyphenyl) methylene]-amino}-1,5-dimethyl-2-phenyl-1,2-dihydro- 3H-pyrazol-3-one [1.344 (3) and 1.292 (4) Å; Huang & Chen, 2005].

In the crystal structure (Fig. 2), the imino N atoms are linked to the phenol O atoms and act as hydrogen-bond acceptors in intramolecular O2—H1O2···N1 interactions (Table 1) (Jeffrey & Saenger, 1991; Jeffrey, 1997; Scheiner, 1997), which generate S(6) ring motifs (Bernstein et al., 1995).

Related literature top

For background to the biological and pharmacological properties of oxazole derivatives, see: Spinelli (1999); Conti et al. (1998); Mishra et al. (1998); Ko et al. (1998); Kang et al. (2000); Huang & Chen (2005). For details of hydrogen bonding and hydrogen-bond motifs see: Jeffrey & Saenger (1991); Bernstein et al. (1995); Jeffrey (1997); Scheiner (1997). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).

Experimental top

A mixture of 5-amino-3,4-dimethylisoxazole (0.50g, 0.0044 mol) and salicyladehyde (0.54g, 0.0044 mol) in methanol (15 mL) was refluxed for 5 h with stirring to give a light yellow precipitate. It was then filtered and washed with methanol to gives the pure Schiff base. Yield: 68%; mp. 116°C. IR (KBr) vmax cm-1: 2922(C—H), 1594 (CO), 1562 (CC), 1152 (C—N). 1H NMR (CDCl3) d: 8.89 (s, 1H, CH olefinic), 7.42 (d, H3, J=1.8Hz), 7.44 (dd, H4, J=7.8Hz), 7.02 (dd, H5, J=7.8Hz), 6.97 (d, H6, J=1.2 Hz), 2.25 (s, CH3), 2.05 (s, CH3).

Refinement top

Atom H1O2 was located from the difference Fourier map and refined freely. The remaining hydrogen atoms were positioned geometrically [C–H = 0.93 Å or 0.96 Å] and were refined using a riding model, with Uiso(H) = 1.2 or 1.5 Ueq(C). A rotating group model was applied to the methyl groups. The crystal is a non-merohedral twin with BASF = 0.166 (4).

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. The asymmetric unit of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme.
[Figure 2] Fig. 2. The crystal packing of the title compound (I).
2-[(E)-(3,4-Dimethylisoxazol-5-yl)iminomethyl]phenol top
Crystal data top
C12H12N2O2Z = 2
Mr = 216.24F(000) = 228
Triclinic, P1Dx = 1.307 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 5.3475 (14) ÅCell parameters from 2862 reflections
b = 8.615 (2) Åθ = 2.4–29.7°
c = 12.321 (3) ŵ = 0.09 mm1
α = 103.696 (5)°T = 100 K
β = 91.486 (5)°Plate, yellow
γ = 94.059 (5)°0.56 × 0.14 × 0.08 mm
V = 549.6 (2) Å3
Data collection top
Bruker APEX DUO CCD area-detector
diffractometer
2467 independent reflections
Radiation source: fine-focus sealed tube1946 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.000
ϕ and ω scansθmax = 27.5°, θmin = 1.7°
Absorption correction: multi-scan
(SADABS; Bruker, 2009)
h = 66
Tmin = 0.951, Tmax = 0.993k = 1110
2467 measured reflectionsl = 615
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)] = 0.070Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.203H atoms treated by a mixture of independent and constrained refinement
S = 1.06 w = 1/[σ2(Fo2) + (0.0657P)2 + 1.1217P]
where P = (Fo2 + 2Fc2)/3
2467 reflections(Δ/σ)max = 0.001
152 parametersΔρmax = 0.40 e Å3
0 restraintsΔρmin = 0.34 e Å3
Crystal data top
C12H12N2O2γ = 94.059 (5)°
Mr = 216.24V = 549.6 (2) Å3
Triclinic, P1Z = 2
a = 5.3475 (14) ÅMo Kα radiation
b = 8.615 (2) ŵ = 0.09 mm1
c = 12.321 (3) ÅT = 100 K
α = 103.696 (5)°0.56 × 0.14 × 0.08 mm
β = 91.486 (5)°
Data collection top
Bruker APEX DUO CCD area-detector
diffractometer
2467 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2009)
1946 reflections with I > 2σ(I)
Tmin = 0.951, Tmax = 0.993Rint = 0.000
2467 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0700 restraints
wR(F2) = 0.203H atoms treated by a mixture of independent and constrained refinement
S = 1.06Δρmax = 0.40 e Å3
2467 reflectionsΔρmin = 0.34 e Å3
152 parameters
Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
O11.0387 (4)1.1305 (2)0.41739 (17)0.0228 (5)
O20.6135 (4)0.7350 (3)0.08828 (18)0.0262 (5)
N10.8330 (5)0.9521 (3)0.2591 (2)0.0194 (5)
N21.2481 (5)1.2478 (3)0.4414 (2)0.0252 (6)
C10.2930 (5)0.7387 (3)0.3499 (3)0.0201 (6)
H1A0.30820.78920.42560.024*
C20.0960 (5)0.6240 (3)0.3108 (3)0.0221 (6)
H2A0.02240.59900.35930.026*
C30.0782 (6)0.5468 (4)0.1976 (3)0.0249 (7)
H3A0.05290.46910.17100.030*
C40.2512 (6)0.5831 (4)0.1235 (3)0.0250 (7)
H4A0.23620.52960.04840.030*
C50.4491 (5)0.7008 (3)0.1626 (2)0.0199 (6)
C60.4711 (5)0.7802 (3)0.2771 (2)0.0186 (6)
C70.6723 (5)0.9024 (3)0.3225 (2)0.0191 (6)
H7A0.68590.94620.39920.023*
C81.0225 (5)1.0682 (3)0.3052 (2)0.0176 (6)
C91.2091 (5)1.1366 (3)0.2539 (2)0.0192 (6)
C101.3428 (5)1.2479 (3)0.3446 (2)0.0195 (6)
C111.2629 (6)1.1010 (4)0.1327 (3)0.0276 (7)
H11A1.14571.01630.09210.041*
H11C1.43051.06850.12290.041*
H11D1.24701.19530.10510.041*
C121.5687 (5)1.3582 (4)0.3386 (3)0.0243 (7)
H12A1.61911.42020.41240.036*
H12D1.52851.42870.29200.036*
H12B1.70341.29630.30750.036*
H1O20.722 (11)0.820 (7)0.132 (5)0.080 (18)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0194 (11)0.0238 (11)0.0233 (11)0.0060 (8)0.0019 (8)0.0042 (8)
O20.0250 (12)0.0281 (11)0.0232 (11)0.0040 (9)0.0061 (9)0.0028 (9)
N10.0170 (12)0.0148 (11)0.0261 (13)0.0009 (9)0.0020 (9)0.0041 (9)
N20.0207 (13)0.0246 (13)0.0290 (14)0.0061 (10)0.0003 (10)0.0062 (10)
C10.0155 (14)0.0176 (13)0.0270 (15)0.0054 (10)0.0036 (11)0.0036 (11)
C20.0152 (14)0.0204 (14)0.0318 (16)0.0021 (11)0.0054 (11)0.0078 (12)
C30.0159 (14)0.0225 (14)0.0353 (17)0.0013 (11)0.0012 (12)0.0063 (12)
C40.0247 (16)0.0227 (15)0.0246 (15)0.0006 (12)0.0007 (12)0.0004 (12)
C50.0164 (14)0.0194 (14)0.0242 (14)0.0026 (11)0.0021 (11)0.0052 (11)
C60.0154 (13)0.0155 (13)0.0256 (14)0.0033 (10)0.0019 (11)0.0054 (11)
C70.0199 (14)0.0158 (13)0.0216 (14)0.0058 (11)0.0019 (11)0.0034 (10)
C80.0140 (13)0.0163 (13)0.0237 (14)0.0051 (10)0.0029 (10)0.0056 (10)
C90.0159 (13)0.0169 (13)0.0262 (15)0.0037 (10)0.0033 (11)0.0074 (11)
C100.0136 (13)0.0169 (13)0.0296 (15)0.0038 (10)0.0020 (11)0.0079 (11)
C110.0272 (16)0.0291 (16)0.0260 (16)0.0009 (13)0.0080 (12)0.0055 (12)
C120.0137 (13)0.0215 (14)0.0392 (17)0.0005 (11)0.0038 (12)0.0100 (12)
Geometric parameters (Å, º) top
O1—C81.357 (3)C4—H4A0.9300
O1—N21.429 (3)C5—C61.412 (4)
O2—C51.353 (4)C6—C71.452 (4)
O2—H1O20.95 (6)C7—H7A0.9300
N1—C71.293 (4)C8—C91.367 (4)
N1—C81.381 (4)C9—C101.426 (4)
N2—C101.308 (4)C9—C111.491 (4)
C1—C21.385 (4)C10—C121.498 (4)
C1—C61.410 (4)C11—H11A0.9600
C1—H1A0.9300C11—H11C0.9600
C2—C31.394 (4)C11—H11D0.9600
C2—H2A0.9300C12—H12A0.9600
C3—C41.387 (4)C12—H12D0.9600
C3—H3A0.9300C12—H12B0.9600
C4—C51.404 (4)
C8—O1—N2107.7 (2)N1—C7—H7A119.1
C5—O2—H1O2103 (3)C6—C7—H7A119.1
C7—N1—C8120.3 (2)O1—C8—C9110.8 (2)
C10—N2—O1105.3 (2)O1—C8—N1119.7 (2)
C2—C1—C6121.2 (3)C9—C8—N1129.5 (3)
C2—C1—H1A119.4C8—C9—C10103.2 (3)
C6—C1—H1A119.4C8—C9—C11128.4 (3)
C1—C2—C3118.9 (3)C10—C9—C11128.4 (3)
C1—C2—H2A120.6N2—C10—C9112.9 (3)
C3—C2—H2A120.6N2—C10—C12119.8 (3)
C4—C3—C2121.6 (3)C9—C10—C12127.3 (3)
C4—C3—H3A119.2C9—C11—H11A109.5
C2—C3—H3A119.2C9—C11—H11C109.5
C3—C4—C5119.7 (3)H11A—C11—H11C109.5
C3—C4—H4A120.2C9—C11—H11D109.5
C5—C4—H4A120.2H11A—C11—H11D109.5
O2—C5—C4118.4 (3)H11C—C11—H11D109.5
O2—C5—C6121.9 (3)C10—C12—H12A109.5
C4—C5—C6119.6 (3)C10—C12—H12D109.5
C1—C6—C5119.0 (3)H12A—C12—H12D109.5
C1—C6—C7118.8 (3)C10—C12—H12B109.5
C5—C6—C7122.2 (3)H12A—C12—H12B109.5
N1—C7—C6121.8 (3)H12D—C12—H12B109.5
C8—O1—N2—C100.3 (3)N2—O1—C8—C90.3 (3)
C6—C1—C2—C31.3 (4)N2—O1—C8—N1179.4 (2)
C1—C2—C3—C40.6 (5)C7—N1—C8—O10.3 (4)
C2—C3—C4—C50.3 (5)C7—N1—C8—C9179.9 (3)
C3—C4—C5—O2179.3 (3)O1—C8—C9—C100.2 (3)
C3—C4—C5—C60.5 (4)N1—C8—C9—C10179.4 (3)
C2—C1—C6—C51.1 (4)O1—C8—C9—C11178.7 (3)
C2—C1—C6—C7179.4 (3)N1—C8—C9—C111.7 (5)
O2—C5—C6—C1180.0 (3)O1—N2—C10—C90.1 (3)
C4—C5—C6—C10.2 (4)O1—N2—C10—C12179.8 (2)
O2—C5—C6—C70.5 (4)C8—C9—C10—N20.0 (3)
C4—C5—C6—C7179.7 (3)C11—C9—C10—N2178.9 (3)
C8—N1—C7—C6179.7 (2)C8—C9—C10—C12180.0 (3)
C1—C6—C7—N1176.1 (3)C11—C9—C10—C121.1 (5)
C5—C6—C7—N14.4 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H1O2···N11.00 (9)1.71 (8)2.648 (5)154 (8)

Experimental details

Crystal data
Chemical formulaC12H12N2O2
Mr216.24
Crystal system, space groupTriclinic, P1
Temperature (K)100
a, b, c (Å)5.3475 (14), 8.615 (2), 12.321 (3)
α, β, γ (°)103.696 (5), 91.486 (5), 94.059 (5)
V3)549.6 (2)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.56 × 0.14 × 0.08
Data collection
DiffractometerBruker APEX DUO CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2009)
Tmin, Tmax0.951, 0.993
No. of measured, independent and
observed [I > 2σ(I)] reflections
2467, 2467, 1946
Rint0.000
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.070, 0.203, 1.06
No. of reflections2467
No. of parameters152
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.40, 0.34

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H1O2···N11.00 (9)1.71 (8)2.648 (5)154 (8)
 

Footnotes

Thomson Reuters ResearcherID: A-3561-2009.

§On secondment to: The Center of Excellence for Advanced Materials Research, King Abdu Aziz University, Jeddah 21589, Saudi Arabia.

Acknowledgements

HKF and MH thank the Malaysian Government and Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012. MH thanks Universiti Sains Malaysia for a post-doctoral research fellowship. AMA, SAK and KAK thank the Chemistry Department, King Abdul Aziz University, Jeddah, Saudi Arabia, for providing research facilities. AMA would also like to thank the deanship of scientific research at KAU for grant No. 171/428.

References

First citationBernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573.  CrossRef CAS Web of Science Google Scholar
First citationBruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationConti, P., Dallanoce, C., Amici, M. D., Micheli, C. D. & Klotz, K. N. (1998). Bioorg. Med. Chem. 6, 401–409.  Web of Science CrossRef CAS PubMed Google Scholar
First citationCosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationHuang, L. & Chen, D.-B. (2005). Acta Cryst. E61, o4169–o4170.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationJeffrey, G. A. (1997). An Introduction to Hydrogen Bonding. Oxford University Press.  Google Scholar
First citationJeffrey, G. A. & Saenger, W. (1991). Hydrogen Bonding in Biological Structures. Berlin: Springer.  Google Scholar
First citationKang, Y. Y., Shin, K. L., Yoo, K. H., Seo, K. J., Hong, C. Y., Lee, C. S., Park, S. Y., Kim, D. J. & Park, S. W. (2000). Bioorg. Med. Chem. Lett. 10, 95–99.  Web of Science CrossRef PubMed CAS Google Scholar
First citationKo, D. H., Maponya, M. F., Khalil, M. A., Oriaku, E. T. & You, Z. (1998). J. Med. Chem. Res. 8, 313–318.  Google Scholar
First citationMishra, A., Jain, K. J. & Asthana, J. G. (1998). Oriental J. Chem. 14, 151–152.  CAS Google Scholar
First citationScheiner, S. (1997). Hydrogen Bonding, A Theoretical Perspective. Oxford University Press.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpinelli, O. A. (1999). Ital. Soc. Chem. 3 301–339.  Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 66| Part 4| April 2010| Pages o773-o774
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds