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Crystallographic and spectroscopic characterization of 5-chloro­pyridine-2,3-di­amine

aDepartment of Chemistry, Vassar College, Poughkeepsie, NY 12604, USA
*Correspondence e-mail: jotanski@vassar.edu

Edited by L. Fabian, University of East Anglia, England (Received 21 June 2017; accepted 14 July 2017; online 21 July 2017)

The two ortho-amino groups of the title compound, C5H6ClN3, twist out of the plane of the mol­ecule to minimize intra­molecular inter­action between the amino hydrogen atoms. In the crystal, the amino groups and the pyridine N atom engage in inter­molecular hydrogen bonding. The mol­ecules pack into spiral hydrogen-bonded columns with offset face-to-face π-stacking.

1. Chemical context

The title compound, 5-chloro­pyridine-2,3-di­amine, is a tri­sub­stituted pyridine featuring ortho-amino groups and a chlorine atom. While all of the sixteen isomers of 5-chloro­pyridine-2,3-di­amine are commercially available, none of their crystal structures have been reported in the literature. 5-Chloro­pyridine-2,3-di­amine may be produced by nitrating 2-amino-5-chloro­pyridine with nitric acid to give 2-amino-3-nitro-5-chloro­pyridine, which is then reduced with sodium di­thio­nite (Israel & Day, 1959[Israel, M. & Day, A. R. (1959). J. Org. Chem. 24, 1455-1460.]). The reduction may also be accomplished with hydrogen gas and Pd/C (Xie et al., 2016[Xie, D., Lu, J., Xie, J., Cui, J., Li, T.-F., Wang, Y.-C., Chen, Y., Gong, N., Li, X.-Y., Fu, L. & Wang, Y.-X. (2016). Eur. J. Med. Chem. 117, 19-32.]). 5-Chloro­pyridine-2,3-di­amine has proven useful as a reagent in complex syntheses, such as in the synthesis of aldose reductase inhibitors with anti­oxidant activity (Han et al., 2016[Han, Z., Hao, X., Ma, B. & Zhu, C. (2016). Eur. J. Med. Chem. 121, 308-317.]), the regioselective functionalization of imidazo­pyridines via alkenylation catalyzed by a Pd/Cu catalyst (Baladi et al., 2016[Baladi, T., Granzhan, A. & Piguel, S. (2016). Eur. J. Org. Chem. pp. 2421-2434.]), the preparation of amino acid oxidase inhibitors (Xie et al., 2016[Xie, D., Lu, J., Xie, J., Cui, J., Li, T.-F., Wang, Y.-C., Chen, Y., Gong, N., Li, X.-Y., Fu, L. & Wang, Y.-X. (2016). Eur. J. Med. Chem. 117, 19-32.]), the preparation of β-glucuronidase inhibitors (Taha et al., 2016[Taha, M., Ismail, N. H., Imran, S., Rashwan, H., Jamil, W., Ali, S., Kashif, S. M., Rahim, F., Salar, U. & Khan, K. M. (2016). Bioorg. Chem. 65, 48-56.]), the preparation of imidazo­pyridine derivatives with activity against MCF-7 breast adenocarcinoma (Püsküllü et al., 2015[Püsküllü, M. O., Karaaslan, C., Bakar, F. & Göker, H. (2015). Chem. Heterocycl. Compd. 51, 723-733.]) and the preparation of di­hydroxy­arene-substituted benzimidazoles, quinazolines and larger rings via cyclo­condensation of di­amines (Los et al., 2012[Los, R., Wesołowska-Trojanowska, M., Malm, A., Karpińska, M. M., Matysiak, J., Niewiadomy, A. & Głaszcz, U. (2012). Heteroat. Chem. 23, 265-275.]).

[Scheme 1]

2. Structural commentary

The mol­ecular structure of the title compound 5-chloro­pyridine-2,3-di­amine (Fig. 1[link]) shows that the mol­ecule is nearly planar with r.m.s deviation from the mean plane of all non-hydrogen atoms of 0.013 (3) Å. The amino groups ortho and meta to the pyridine nitro­gen atom twist out of the plane of the mol­ecule in such a way as to minimize contact with one another, with NH2 plane to mol­ecular plane angles of 45 (3) and 34 (3)° for N2 and N3, respectively. It is notable that the achiral title compound crystallizes in a non-enanti­ogenic (Söhncke) space group, although not a polar space group.

[Figure 1]
Figure 1
A view of 5-chloro­pyridine-2,3-di­amine (I)[link] with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level.

3. Supra­molecular features

Notable inter­molecular inter­actions observed in the structure of 5-chloro­pyridine-2,3-di­amine (I)[link] include Namine—H⋯Npyr and Namine—H⋯Namine hydrogen bonding inter­actions and offset face-to-face π-stacking. The mol­ecules connect into a one-dimensional strip running parallel to the crystallographic b axis (Fig. 2[link]) with long N3amine—H21⋯N2iiamine [symmetry code (ii) −x + 2, y − [{1\over 2}], −z + [{3\over 2}]] and N3amine—H22⋯N1iiipyr [symmetry code (iii) −x + 2, y + [{1\over 2}], −z + [{3\over 2}]] hydrogen bonding inter­actions with donor–acceptor distances of 3.250 (4) and 3.075 (4) Å, respectively (Table 1[link]). A third Namine—H⋯Npyr hydrogen-bonding contact and offset face-to-face π-stacking can be seen to extend along the crystallographic a axis (Fig. 3[link]), acting to link the one-dimensional strips into two-dimensional sheets. The N2amine—H12⋯N1pyri [symmetry code (i) −x + 1, y + [{1\over 2}], −z + [{3\over 2}]] contact exhibits a donor–acceptor distance 3.264 (3) Å. The π-stacking is characterized by a centroid-to-centroid distance of 3.756 (1) Å, plane-to-plane distances of 3.414 (2) Å and a ring offset of 1.568 (3) Å (Hunter & Saunders, 1990[Hunter, C. A. & Sanders, J. K. M. (1990). J. Am. Chem. Soc. 112, 5525-5534.]; Lueckheide et al., 2013[Lueckheide, M., Rothman, N., Ko, B. & Tanski, J. M. (2013). Polyhedron, 58, 79-84.]). Alternatively, the three hydrogen-bonding contacts and the π-stacking taken together can be seen to form a spiral of 5-chloro­pyridine-2,3-di­amine (I)[link] mol­ecules extending along the a-axis direction (Fig. 4[link]).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N2—H12⋯N1i 0.86 (2) 2.48 (3) 3.264 (3) 151 (3)
N3—H21⋯N2ii 0.89 (2) 2.38 (2) 3.250 (4) 166 (3)
N3—H22⋯N1iii 0.90 (2) 2.19 (2) 3.075 (4) 167 (3)
Symmetry codes: (i) [-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]; (ii) [-x+2, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]; (iii) [-x+2, y+{\script{1\over 2}}, -z+{\script{3\over 2}}].
[Figure 2]
Figure 2
A view of the inter­molecular N3amine—H21⋯N2iiamine and N3amine—H22⋯N1iiipyr one-dimensional hydrogen bonding in 5-chloro­pyridine-2,3-di­amine (I)[link]. [Symmetry codes: (ii) −x + 2, y − [{1\over 2}], −z + [{3\over 2}]; (iii) −x + 2, y + [{1\over 2}], −z + [{3\over 2}].]
[Figure 3]
Figure 3
A view of the packing in 5-chloro­pyridine-2,3-di­amine (I)[link] indicating hydrogen bonding connecting the one-dimensional strips into two-dimensional sheets along with offset face-to-face π-stacking.
[Figure 4]
Figure 4
A view of the spiral hydrogen-bonded chain in 5-chloro­pyridine-2,3-di­amine (I)[link] highlighting the N2amine—H12⋯N1ipyr contact. [Symmetry code: (i) −x + 1, y + [{1\over 2}], −z + [{3\over 2}].]

4. Database survey

The Cambridge Structural Database (Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) contains about fifty structurally similar compounds to 5-chloro­pyridine-2,3-di­amine (I)[link], with 2-amino-5-chloro­pyridine (AMCLPY12) (Pourayoubi et al., 2007[Pourayoubi, M., Ghadimi, S. & Ebrahimi Valmoozi, A. A. (2007). Acta Cryst. E63, o4631.]) and 2-amino-3-chloro­pyridine (URAXER) (Hu et al., 2011[Hu, Z.-N., Yang, H.-B., Luo, H. & Li, B. (2011). Acta Cryst. E67, o1138.]) being the most chemically and structurally similar. The C—Cl bond length in the title compound, with distance 1.748 (3) Å, is comparable to those in 2-amino-5-chloro­pyridine (AMCLPY12) and 2-amino-3-chloro­pyridine (URAXER), with distances 1.7404 (14) and 1.735 (3) Å, respectively. The C—Namine distances in the title compound, 1.406 (4) and 1.385 (4) Å, however, are somewhat longer than in 2-amino-5-chloro­pyridine (AMCLPY12) [1.3602 (19) Å] and 2-amino-3-chloro­pyridine (URAXER) [1.351 (4) Å]. 2-amino-5-chloro­pyridine (AMCLPY12), which does not have the meta-NH2 substitution of the title compound, packs in a herringbone formation featuring centrosymmetric head-to-tail Namine—H⋯Npyr hydrogen bonding dimers with donor–acceptor distance 3.031 (2) Å. 2-Amino-3-chloro­pyridine (URAXER), has a meta-Cl substitution in place of the meta-NH2 in the title compound. Like 2-amino-5-chloro­pyridine (AMCLPY12), 2-amino-3-chloro­pyridine (URAXER) features a herringbone packing with centrosymmetric head-to-tail Namine—H⋯Npyr hydrogen-bonded dimer with a similar donor–acceptor distance of 3.051 (5) Å. The similar hydrogen-bonding motif in these two related compounds differs from the title compound, which does not exhibit centrosymmetric hydrogen-bonding dimerization. 2-Amino-3-chloro­pyridine (URAXER) also has short inter­molecular Cl⋯Cl inter­actions of 3.278 (3) Å, where no such short halogen–halogen contact was observed in 2-amino-5-chloro­pyridine (AMCLPY12) or the title compound.

5. Synthesis and crystallization

5-Chloro­pyridine-2,3-di­amine (97%) was purchased from Aldrich Chemical Company, USA. A single crystal suitable for analysis was selected from the purchased sample and used as received.

6. Analytical data

1H NMR (Bruker Avance 400 MHz, DMSO d6): δ 4.99 (br s, 2 H, NH2), 5.55 (br s, 2 H, NH2), 6.69 (d, 1 H, J = 2.3 Hz, Car­ylH), 7.21 (d, 1 H, J = 2.3 Hz, Car­ylH). 13C NMR (13C{1H}, 100.6 MHz, DMSO d6): δ 116.58 (Car­ylH), 118.38 (Car­yl), 131.32 (Car­yl), 131.66 (Car­ylH), 147.10 (Car­yl). IR (Thermo Nicolet iS50, ATR, cm−1): 3392 (m, N—H str), 3309 (m, N—H str), 3172 (m, aryl C—H str), 1637 (s, aryl C=C str), 1572 (m), 1472 (s), 1421 (m), 1347 (w), 1307 (w), 1280 (w), 1240 (m), 1068 (m), 939 (w), 887 (w), 861 (m), 792 (m), 770 (m), 680 (s), 630 (s), 568 (s), 490 (s), 449 (s). GC/MS (Hewlett-Packard MS 5975/GC 7890): M+ = 143 (calc. exact mass = 143.03).

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms on carbon were included in calculated positions and refined using a riding model with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C) of the aryl C-atoms. The positions of the four amino hydrogen atoms were found in the difference map and they were refined semi-freely using a distance restraint d(N—H) = 0.91 Å, and Uiso(H) = 1.2Ueq(N).

Table 2
Experimental details

Crystal data
Chemical formula C5H6ClN3
Mr 143.58
Crystal system, space group Orthorhombic, P212121
Temperature (K) 125
a, b, c (Å) 3.7565 (8), 8.7002 (17), 18.350 (4)
V3) 599.7 (2)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.53
Crystal size (mm) 0.10 × 0.05 × 0.04
 
Data collection
Diffractometer Bruker APEXII CCD
Absorption correction Multi-scan (SADABS; Bruker, 2013[Bruker (2013). SAINT, SADABS and APEX2. Bruxer AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.75, 0.98
No. of measured, independent and observed [I > 2σ(I)] reflections 14989, 1845, 1477
Rint 0.087
(sin θ/λ)max−1) 0.714
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.084, 1.07
No. of reflections 1845
No. of parameters 94
No. of restraints 4
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.37, −0.38
Absolute structure Flack x determined using 511 quotients [(I+)−(I)]/[(I+)+(I)] (Parsons et al., 2013[Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249-259.])
Absolute structure parameter 0.01 (6)
Computer programs: APEX2 and SAINT (Bruker, 2013[Bruker (2013). SAINT, SADABS and APEX2. Bruxer AXS Inc., Madison, Wisconsin, USA.]), SHELXT2014 (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), SHELXTL2014 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]) and Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]).

Supporting information


Computing details top

Data collection: APEX2 (Bruker, 2013); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: SHELXTL2014 (Sheldrick, 2008); software used to prepare material for publication: SHELXTL2014 (Sheldrick, 2008), OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2008).

5-Chloropyridine-2,3-diamine top
Crystal data top
C5H6ClN3Dx = 1.590 Mg m3
Mr = 143.58Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121Cell parameters from 4306 reflections
a = 3.7565 (8) Åθ = 2.6–29.7°
b = 8.7002 (17) ŵ = 0.53 mm1
c = 18.350 (4) ÅT = 125 K
V = 599.7 (2) Å3Plate, colourless
Z = 40.10 × 0.05 × 0.04 mm
F(000) = 296
Data collection top
Bruker APEXII CCD
diffractometer
1845 independent reflections
Radiation source: fine-focus sealed tube1477 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.087
Detector resolution: 8.3333 pixels mm-1θmax = 30.5°, θmin = 2.2°
φ and ω scansh = 55
Absorption correction: multi-scan
(SADABS; Bruker, 2013)
k = 1212
Tmin = 0.75, Tmax = 0.98l = 2626
14989 measured reflections
Refinement top
Refinement on F2Hydrogen site location: mixed
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.041 w = 1/[σ2(Fo2) + (0.0308P)2 + 0.2158P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.084(Δ/σ)max < 0.001
S = 1.07Δρmax = 0.37 e Å3
1845 reflectionsΔρmin = 0.38 e Å3
94 parametersAbsolute structure: Flack x determined using 511 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
4 restraintsAbsolute structure parameter: 0.01 (6)
Special details top

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cl10.5035 (2)0.46707 (8)0.47194 (3)0.01872 (16)
N10.8538 (6)0.4647 (3)0.67658 (12)0.0148 (5)
N20.5894 (7)0.8717 (3)0.67694 (14)0.0153 (5)
H110.464 (9)0.928 (3)0.6466 (14)0.018*
H120.530 (10)0.872 (3)0.7224 (12)0.018*
N30.8976 (7)0.6490 (3)0.76777 (13)0.0154 (5)
H211.032 (9)0.580 (3)0.7905 (15)0.018*
H220.955 (10)0.748 (3)0.7772 (16)0.018*
C10.7608 (8)0.4231 (3)0.60820 (16)0.0157 (6)
H10.79770.31990.59310.019*
C20.6148 (7)0.5258 (4)0.56011 (14)0.0138 (5)
C30.5497 (7)0.6759 (3)0.58152 (14)0.0121 (6)
H30.4450.7470.54860.015*
C40.6388 (7)0.7209 (3)0.65122 (15)0.0122 (6)
C50.8035 (7)0.6100 (3)0.69716 (15)0.0125 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0204 (3)0.0220 (3)0.0138 (3)0.0021 (4)0.0034 (3)0.0035 (3)
N10.0154 (11)0.0144 (11)0.0145 (11)0.0014 (11)0.0007 (9)0.0001 (11)
N20.0182 (14)0.0137 (12)0.0140 (11)0.0036 (9)0.0003 (9)0.0000 (9)
N30.0162 (14)0.0152 (12)0.0148 (11)0.0009 (10)0.0036 (9)0.0004 (10)
C10.0176 (15)0.0126 (14)0.0171 (14)0.0008 (11)0.0014 (12)0.0019 (11)
C20.0101 (12)0.0202 (13)0.0112 (11)0.0036 (12)0.0002 (9)0.0016 (12)
C30.0061 (14)0.0157 (12)0.0146 (12)0.0022 (10)0.0009 (10)0.0040 (10)
C40.0064 (12)0.0142 (14)0.0160 (14)0.0003 (10)0.0026 (11)0.0004 (11)
C50.0066 (13)0.0184 (15)0.0125 (13)0.0017 (11)0.0021 (10)0.0011 (11)
Geometric parameters (Å, º) top
Cl1—C21.748 (3)N3—H220.90 (2)
N1—C51.333 (4)C1—C21.371 (4)
N1—C11.352 (4)C1—H10.95
N2—C41.406 (4)C2—C31.385 (4)
N2—H110.88 (2)C3—C41.379 (4)
N2—H120.86 (2)C3—H30.95
N3—C51.385 (4)C4—C51.423 (4)
N3—H210.89 (2)
C5—N1—C1118.7 (3)C1—C2—Cl1120.1 (2)
C4—N2—H11112 (2)C3—C2—Cl1119.7 (2)
C4—N2—H12111 (2)C4—C3—C2119.2 (3)
H11—N2—H12118 (3)C4—C3—H3120.4
C5—N3—H21115 (2)C2—C3—H3120.4
C5—N3—H22118 (2)C3—C4—N2123.0 (3)
H21—N3—H22114 (3)C3—C4—C5117.5 (3)
N1—C1—C2121.8 (3)N2—C4—C5119.4 (3)
N1—C1—H1119.1N1—C5—N3117.5 (3)
C2—C1—H1119.1N1—C5—C4122.5 (2)
C1—C2—C3120.2 (3)N3—C5—C4119.9 (3)
C5—N1—C1—C20.5 (4)C1—N1—C5—N3179.3 (2)
N1—C1—C2—C31.7 (4)C1—N1—C5—C43.3 (4)
N1—C1—C2—Cl1179.3 (2)C3—C4—C5—N14.0 (4)
C1—C2—C3—C41.0 (4)N2—C4—C5—N1179.0 (3)
Cl1—C2—C3—C4180.0 (2)C3—C4—C5—N3179.8 (3)
C2—C3—C4—N2178.5 (3)N2—C4—C5—N33.2 (4)
C2—C3—C4—C51.7 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H12···N1i0.86 (2)2.48 (3)3.264 (3)151 (3)
N3—H21···N2ii0.89 (2)2.38 (2)3.250 (4)166 (3)
N3—H22···N1iii0.90 (2)2.19 (2)3.075 (4)167 (3)
Symmetry codes: (i) x+1, y+1/2, z+3/2; (ii) x+2, y1/2, z+3/2; (iii) x+2, y+1/2, z+3/2.
 

Acknowledgements

This work was supported by Vassar College. X-ray facilities were provided by the US National Science Foundation (grants Nos. 0521237 and 0911324 to JMT). NMR facilities were provided by the US National Science Foundation (grant No. 1526982 to JMT and TG). We acknowledge the Salmon Fund of Vassar College for funding publication expenses.

Funding information

Funding for this research was provided by: National Science Foundation, Directorate for Mathematical and Physical Sciences (grant No. 0521237 to Joseph M. Tanski); National Science Foundation, Directorate for Mathematical and Physical Sciences (grant No. 0911324 to Joseph M. Tanski); National Science Foundation, Directorate for Mathematical and Physical Sciences (grant No. 1526982 to Joseph M. Tanski, Teresa A. Garrett).

References

First citationBaladi, T., Granzhan, A. & Piguel, S. (2016). Eur. J. Org. Chem. pp. 2421–2434.  CrossRef Google Scholar
First citationBruker (2013). SAINT, SADABS and APEX2. Bruxer AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationDolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationGroom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationHan, Z., Hao, X., Ma, B. & Zhu, C. (2016). Eur. J. Med. Chem. 121, 308–317.  CrossRef CAS PubMed Google Scholar
First citationHu, Z.-N., Yang, H.-B., Luo, H. & Li, B. (2011). Acta Cryst. E67, o1138.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationHunter, C. A. & Sanders, J. K. M. (1990). J. Am. Chem. Soc. 112, 5525–5534.  CrossRef CAS Web of Science Google Scholar
First citationIsrael, M. & Day, A. R. (1959). J. Org. Chem. 24, 1455–1460.  CrossRef CAS Google Scholar
First citationLos, R., Wesołowska-Trojanowska, M., Malm, A., Karpińska, M. M., Matysiak, J., Niewiadomy, A. & Głaszcz, U. (2012). Heteroat. Chem. 23, 265–275.  CrossRef CAS Google Scholar
First citationLueckheide, M., Rothman, N., Ko, B. & Tanski, J. M. (2013). Polyhedron, 58, 79–84.  Web of Science CSD CrossRef CAS Google Scholar
First citationMacrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
First citationParsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationPourayoubi, M., Ghadimi, S. & Ebrahimi Valmoozi, A. A. (2007). Acta Cryst. E63, o4631.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationPüsküllü, M. O., Karaaslan, C., Bakar, F. & Göker, H. (2015). Chem. Heterocycl. Compd. 51, 723–733.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015a). Acta Cryst. A71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015b). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationTaha, M., Ismail, N. H., Imran, S., Rashwan, H., Jamil, W., Ali, S., Kashif, S. M., Rahim, F., Salar, U. & Khan, K. M. (2016). Bioorg. Chem. 65, 48–56.  CrossRef CAS PubMed Google Scholar
First citationXie, D., Lu, J., Xie, J., Cui, J., Li, T.-F., Wang, Y.-C., Chen, Y., Gong, N., Li, X.-Y., Fu, L. & Wang, Y.-X. (2016). Eur. J. Med. Chem. 117, 19–32.  CrossRef CAS PubMed Google Scholar

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