Literature DB >> 29850053

Crystal structures of 5,5'-bis(-hydroxy-methyl)-3,3'-biisoxazole and 4,4',5,5'-tetrakis-(hydroxy-methyl)-3,3'-biisoxazole.

Rosario C Sausa1, Leah A Wingard2, Pablo E Guzmán2, Rose A Pesce-Rodriguez1, Jesse J Sabatini2, Peter Y Zavalij3.   

Abstract

The mol-ecular structure of 5,5'-bis(-hydroxy-methyl)-3,3'-biisoxazole, C8H8N2O4 (1), is composed of two trans planar isoxazole rings [r.m.s deviation = 0.006 (1) Å], each connected with a methyl hydroxyl group. Similarly, the structure of 4,4',5,5'-tetrakis-(hydroxy-methyl)-3,3'-biisoxazole, C10H12N2O6 (2), is composed of two planar isoxazole rings [r.m.s. deviation = 0.002 (1) Å], but with four hydroxymethyl groups as substituents. Both mol-ecules sit on a center of inversion, thus Z' = 0.5. The crystal structures are stabilized by networks of O-H⋯N [for (1)] and O-H⋯O hydrogen-bonding inter-actions [for (2)], giving rise to corrugated supra-molecular planes. The isoxazole rings are packed in a slip-stacked fashion, with centroid-to-centroid distances of 4.0652 (1) Å for (1) (along the b-axis direction) and of 4.5379 (Å) for (2) (along the a-axis direction).

Entities:  

Keywords:  FTIR; crystal structure; hy­droxy­methyl-biisoxazole

Year:  2018        PMID: 29850053      PMCID: PMC5956336          DOI: 10.1107/S2056989018000828

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

The five-membered, heterocyclic isoxazole moiety forms the basis for a number of medical and agricultural products, as well as energetic materials (Galenko et al., 2015 ▸; Sausa et al., 2017 ▸; Wingard et al., 2017a ▸,b ▸; Sysak & Obmińska-Mrukowicz, 2017 ▸). Its versatility stems from the electronegative oxygen and nitro­gen atoms, which provide the ring nucleophilic activity, and its three carbon atoms, which afford the addition of a variety of functional groups. The title compounds 5,5′-bis(hydroxy­methyl)-3,3′-biisoxazole (1) and 4,4′,5,5′-tetrakis(hydroxy­methyl)-3,3′-biisoxazole (2) exhibit two isoxazole rings, each attached with one or two hydroxymethy groups. These compounds have been synthesized recently in our laboratory as useful precursors to a new class of energetic materials. The addition of nitric acid to the title compounds results in nitrate esterification, yielding the energetic materials biisoxazole­bis(methyl­ene dinitrate) (3) and biisoxazole­tetra­kis­(methyl nitrate) (4), where a nitrate functional group replaces the hydrogen atom in the hydroxyl groups (Wingard et al., 2017a ▸,b ▸). These derivative compounds are potential energetic plasticizing ingredients in nitro­cellulose or melt-castable formulations because the rings present Lewis-base behavior towards electrophilic nitro­cellulose and the alkyl nitric esters afford miscibility and compatibility with conventional energetic plasticizers.

Structural commentary

The title compounds exhibit mol­ecular structures typical of biisoxazole derivatives. Fig. 1 ▸ reveals that the isoxazole rings of (1) exhibit a trans planar configuration [r.m.s deviation = 0.0009 (1) Å], suggesting a delocalized aromatic π system. The C4 atom is nearly coplanar with the ring (atom-to-mean plane distance = 0.006 Å), whereas the C4—O2 bond is twisted slightly out of the plane, as evidenced by the torsion angles C2—C1—C4—O2 = −13.3 (2)° and O1—C1—C4—O2 = 167.55 (11)°. Atoms C1/C4/O2 form a plane that subtends a dihedral angle of 12.72 (1)° with respect to the isoxazole ring. Similarly, the isoxazole rings of (2) are nearly planar [r.m.s deviation = 0.002 (1) Å]; however, the corresponding O2—C4 bond is twisted more out of plane than that of compound (1), as evidenced by the magnitude of the torsion angle O2—C4—C1—O1 = −54.93 (11)°. For comparison, the torsion angle formed by atoms O3—C5—C2—C1 is −110.02 (11)°. The atoms O2/C4/C1 and O3/C5/C2 form planes subtending dihedral angles of 53.78 (8) and 69.37 (7)° with respect to the isoxazole ring. Superimposition of the ring atoms of both structures (see Fig. 2 ▸) yields an r.m.s. deviation of 0.01 Å. Finally, compound (2) exhibits a weak intra­molecular inter­action involving atoms O3—H3A and N1iii [see Table 2 ▸ for the geometrical parameters; symmetry code: (iii) = −x + 2, −y + 1, −z + 1.]
Figure 1

Mol­ecular conformation and atom-numbering scheme of compounds (1) and (2). Non-labeled atoms of both structures are generated by inversion (−x + 2, −y + 1, −z + 1). Non-hydrogen atoms are shown as 50% probability displacement ellipsoids.

Figure 2

An overlay of the asymmetric units of compounds (1) and (2), depicted in red and green, respectively.

Table 2

Hydrogen-bond geometry (Å, °) for (II)

D—H⋯A D—HH⋯A DA D—H⋯A
O2—H2A⋯O3i 0.849 (18)1.849 (18)2.6936 (11)172.8 (16)
O3—H3A⋯O2ii 0.792 (19)2.085 (19)2.7898 (11)148.3 (18)
O3—H3A⋯N1iii 0.792 (19)2.550 (19)3.0728 (12)125.0 (16)

Symmetry codes: (i) ; (ii) ; (iii) .

Supra­molecular features

Inter­molecular hydrogen bonding plays a key role in the stabilization of the crystal structures of the title compounds. Figs. 3 ▸ and 4 ▸ show the packing of (1) and (2), respectively, and Tables 1 ▸ and 2 ▸ list their hydrogen-bonding geometries. Compound (1) displays hydrogen bonding between the oxygen atoms O2, belonging to the hy­droxy groups, and the N1 atoms of the isoxazole rings of adjacent mol­ecules, generating a supra­molecular framework parallel to (01) [O2⋯N1i = 2.8461 (15) Å; symmetry code: (i) x − , −y + , z − ]. In contrast, compound (2) forms a network of hydrogen bonds involving the hy­droxy groups O2—H2A and O3—H3A of adjacent mol­ecules, so that each OH group acts both as donor and acceptor [see Table 2 ▸ and Fig. 4 ▸; O2⋯O3i = 2.694 (1) Å; symmetry code: (i) −x + 1, y + , −z + ; O3⋯O2ii = 2.790 (1) Å; symmetry code: (ii) x + 1, −y + , z + ]. In this way, each mol­ecule forms eight hydrogen bonds with the four closest surrounding analogues, giving rise to corrugated planes parallel to (02).
Figure 3

Crystal packing of (1) viewed along the a-axis direction. Dashed lines represent O2—H2A⋯N1i hydrogen bonds; symmetry code: (i) x − , −y + , z − .

Figure 4

Crystal packing of (2) viewed along the a-axis direction. Dashed lines represent O2—H2A⋯O3i and O3—H3A⋯O2ii hydrogen bonds; symmetry codes: (i) −x + 1, y + , −z + ; (ii) x + 1, −y + , z + .

Table 1

Hydrogen-bond geometry (Å, °) for (I)

D—H⋯A D—HH⋯A DA D—H⋯A
O2—H2A⋯N1i 0.822.032.8461 (15)171

Symmetry code: (i) .

The crystal structure of (1) reveals a slip-stacked geometry of the rings in the b-axis direction, with centroid-to-centroid distances of 4.0652 (1) Å and plane-to-plane shifts of 2.256 (2) Å. In contrast, in compound (2) the rings are stacked along the a-axis direction, with centroid-to-centroid distances of 4.5379 (4) Å and plane-to-plane shifts of 2.683 (2) Å.

Database survey

A search of the Cambridge Structural Database (CSD web inter­face, December 2017; Groom et al., 2016 ▸) and the Crystallography Open Database (Gražulis et al., 2009 ▸) yielded the crystal structures of several compounds containing the biisoxazole moiety. For examples, see Cannas & Marongiu (1967 ▸) (CCDC 1111317, BIOXZL); van der Peet et al. (2013 ▸) (CCDC 935274, LIRLEF); Sausa et al. (2017 ▸) (CCDC 1540757, TAXDUU); Wingard et al. (2017b ▸) (CCDC 1529260, WANVEP). Compounds (3) (Sausa et al., 2017 ▸) and (4) (Wingard et al. 2017b ▸) are noteworthy because they are nitrate derivatives of the title compounds (1) and (2), respectively, with the hydrogen atoms in the OH groups replaced by NO2 moieties. A superimposition of the respective isoxazole rings of compound (1) and (3) yields an r.m.s. deviation of 0.004 Å (Fig. 5 ▸A). In both mol­ecules, the rings adopt a trans conformations; however, in (1) the O1 and O2 atoms are in a trans conformation with respect to the C1—C4 bond, whereas in (3) the corresponding O atoms are in a cis conformation. In (1), the plane encompassing the atoms O2, C4, and C1 forms a dihedral angle of 12.72 (1)° with respect to the mean plane of the isoxazole ring, in contrast to a value of 66.8 (2)° in (3) for the corresponding atoms. A similar comparison between (2) and (4) yields an r.m.s. deviation of 0.01 Å for the superimposition of the isoxazole rings, and dihedral angles of 53.78 (8) and 69.37 (7)° for (2) (planes formed by the atoms O2/C4/C1 and O3/C5/C2, respectively) compared to those of 84.54 (14) and 84.81 (18)° or 79.19 (15) and 82.32 (17)° for (4) (Fig. 5 ▸B). The most striking supra­molecular difference between the title compounds and (3) and (4) is that the former exhibit hydrogen bonding, which contributes to the stability of their crystal structure.
Figure 5

Overlays of the asymmetric units of (1) and (3) (A) and (2) and (4) (B).

Synthesis and crystallization

The synthesis of the title compounds has been reported recently (Wingard et al., 2017 ▸). Briefly, they were prepared by [3 + 2] cyclo­addition of di­chloro­glyoxime and alcohol. In the case of compound (1), a saturated solution of sodium bicarbonate was added to a solution of di­chloro­glyoxime (30 g), propargyl alcohol (55.2 ml), and methanol (1900 ml) over 6 h. Once the reaction was complete, the product was stirred for an additional 10 h and the remaining solvent evaporated. A yield of 75% was obtained after the product was washed with distilled water, collected by Büchner filtration, and then dried. Compound (2) was prepared by adding dropwise a di­chloro­glyoxime and butyl alcohol solution (0.8 M) to a refluxing solution comprising NaHCO3 (6.7 g), 2-butyne-1,4-diol (13.72 g), and butyl alcohol (200 ml). Once the reaction was complete, the product was cooled to room temperature and the remaining solvent evaporated. Then, the product was washed with distilled water, filtered, and dried, resulting in a yield of 68%. Slow solvent evaporation of the title compounds in methanol yielded suitable single crystals for the X-ray diffraction experiments at 150K. We note the title compounds have nearly the same density (1.596 vs 1.597 Mg m−3), given that their mol­ecular mass and cell constants are quite different. Fig. 6 ▸ shows the FTIR spectra of (1) and (2) recorded with a Nicolet iS50 spectrophotometer, using attenuated total reflectance. The intense peak frequencies (cm−1) are listed as follows: Compound (1): 3371.83, 3126.65, 1596.96, 1415.14, 1360.62, 1268.13, 1237.16, 1080.70, 1058.61, 1026.40, 993.24, 929.53, 901.95, 828.87, 746.83, 653.69, 621.96, and 424.11. Compound (2): 3234.89, 1623.59, 1456.55, 1418.41, 1354.66, 1261.30, 1185.44, 1128.41, 1046.52, 1011.82, 984.07, 964.14, 931.24, 906.80, 764.50, 725.86, 641.00, 576.90, 475.85, and 449.97.
Figure 6

FTIR spectra of the title compounds.

Refinement

Crystal data, data collection, structure solution and refinement details are summarized in Table 3 ▸. The hydrogen atoms for compound (1) were refined using a riding model with C—H = 0.93 or 0.98 Å and U iso(H) = 1.2U eq(C) and O—H = 0.74–0.85 Å and U iso(H) = 1.5U eq(O), whereas for compound (2) all the hydrogen atoms were refined independently including isotropic displacement parameters.
Table 3

Experimental details

 (I)(II)
Crystal data
Chemical formulaC8H8N2O4 C10H12N2O6
M r 196.16256.22
Crystal system, space groupMonoclinic, P21/n Monoclinic, P21/c
Temperature (K)150150
a, b, c (Å)7.7824 (3), 4.0652 (1), 13.2109 (5)4.5379 (4), 9.9195 (8), 12.0177 (9)
β (°)102.334 (4)99.9312 (11)
V3)408.31 (2)532.86 (8)
Z 22
Radiation typeMo KαMo Kα
μ (mm−1)0.130.13
Crystal size (mm)0.35 × 0.25 × 0.050.49 × 0.20 × 0.11
 
Data collection
DiffractometerRigaku Oxford DiffractionSuperNova, Dualflex, EosS2Bruker SMART APEXII CCD
Absorption correctionMulti-scan (CrysAlis PRO; Rigaku OD, 2015; Bourhis et al., 2015)Multi-scan (SADABS; Sheldrick, 2008)
T min, T max 0.207, 1.0000.904, 0.985
No. of measured, independent and observed [I > 2σ(I)] reflections3474, 823, 7547638, 1737, 1570
R int 0.0270.019
(sin θ/λ)max−1)0.6240.730
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.033, 0.086, 1.040.034, 0.072, 1.00
No. of reflections8231737
No. of parameters66106
H-atom treatmentH-atom parameters constrainedAll H-atom parameters refined
Δρmax, Δρmin (e Å−3)0.28, −0.150.44, −0.22

Computer programs: CrysAlis PRO (Rigaku OD, 2015 ▸), APEX2, XSHELL and SAINT (Bruker, 2010 ▸), SHELXT (Sheldrick, 2015a ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015b ▸), OLEX2 (Dolomanov et al., 2009 ▸), Mercury (Macrae et al., 2008 ▸) and PLATON (Spek, 2009 ▸).

Crystal structure: contains datablock(s) 1, 2. DOI: 10.1107/S2056989018000828/xi2007sup1.cif Structure factors: contains datablock(s) 1, 2. DOI: 10.1107/S2056989018000828/xi20071sup3.hkl Structure factors: contains datablock(s) 2. DOI: 10.1107/S2056989018000828/xi20072sup2.hkl Click here for additional data file. Supporting information file. DOI: 10.1107/S2056989018000828/xi20071sup4.cml Click here for additional data file. Supporting information file. DOI: 10.1107/S2056989018000828/xi20072sup5.cml CCDC references: 1816712, 1816711 Additional supporting information: crystallographic information; 3D view; checkCIF report
C8H8N2O4F(000) = 204
Mr = 196.16Dx = 1.596 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 7.7824 (3) ÅCell parameters from 1980 reflections
b = 4.0652 (1) Åθ = 2.8–26.2°
c = 13.2109 (5) ŵ = 0.13 mm1
β = 102.334 (4)°T = 150 K
V = 408.31 (2) Å3Block, colorless
Z = 20.35 × 0.25 × 0.05 mm
Rigaku Oxford DiffractionSuperNova, Dualflex, EosS2 diffractometer823 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Mo) X-ray Source754 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.027
Detector resolution: 8.0945 pixels mm-1θmax = 26.3°, θmin = 2.8°
ω scansh = −9→9
Absorption correction: multi-scan CrysAlisPro (Rigaku OD, 2015; Bourhis et al., 2015)k = −5→5
Tmin = 0.207, Tmax = 1.000l = −16→16
3474 measured reflections
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.033w = 1/[σ2(Fo2) + (0.040P)2 + 0.183P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.086(Δ/σ)max < 0.001
S = 1.03Δρmax = 0.28 e Å3
823 reflectionsΔρmin = −0.15 e Å3
66 parametersExtinction correction: SHELXL-2016/4 (Sheldrick 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.041 (8)
Primary atom site location: dual
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.
xyzUiso*/Ueq
C10.64217 (17)0.3456 (3)0.39844 (9)0.0193 (3)
C20.78918 (17)0.5023 (3)0.38810 (10)0.0207 (3)
H20.8081280.6214130.3313700.025*
C30.90869 (16)0.4449 (3)0.48325 (9)0.0188 (3)
C40.46651 (17)0.3002 (3)0.32830 (10)0.0230 (3)
H4A0.4537880.0762290.3024460.028*
H4B0.3738260.3437340.3652860.028*
N10.83872 (14)0.2665 (3)0.54646 (8)0.0238 (3)
O10.66636 (12)0.2010 (2)0.49285 (7)0.0240 (3)
O20.45577 (14)0.5241 (3)0.24526 (7)0.0304 (3)
H2A0.4125480.4315900.1905840.046*
U11U22U33U12U13U23
C10.0199 (7)0.0198 (7)0.0165 (6)0.0029 (5)0.0004 (5)−0.0032 (5)
C20.0194 (7)0.0238 (7)0.0174 (6)0.0007 (5)0.0009 (5)−0.0005 (5)
C30.0173 (7)0.0209 (7)0.0174 (6)0.0021 (5)0.0019 (5)−0.0029 (5)
C40.0190 (7)0.0249 (7)0.0226 (7)−0.0005 (5)−0.0009 (5)−0.0054 (5)
N10.0173 (6)0.0315 (7)0.0198 (6)−0.0029 (5)−0.0019 (4)−0.0002 (5)
O10.0180 (5)0.0319 (6)0.0199 (5)−0.0052 (4)−0.0008 (4)0.0003 (4)
O20.0342 (6)0.0275 (6)0.0230 (5)−0.0011 (4)−0.0087 (4)−0.0024 (4)
C1—C21.3419 (19)C3—N11.3093 (17)
C1—C41.4901 (17)C4—H4A0.9700
C1—O11.3550 (15)C4—H4B0.9700
C2—H20.9300C4—O21.4142 (17)
C2—C31.4143 (18)N1—O11.4021 (14)
C3—C3i1.465 (2)O2—H2A0.8200
C2—C1—C4133.19 (12)C1—C4—H4A110.3
C2—C1—O1110.24 (11)C1—C4—H4B110.3
O1—C1—C4116.57 (11)H4A—C4—H4B108.5
C1—C2—H2127.9O2—C4—C1107.28 (11)
C1—C2—C3104.14 (11)O2—C4—H4A110.3
C3—C2—H2127.9O2—C4—H4B110.3
C2—C3—C3i129.00 (15)C3—N1—O1105.45 (10)
N1—C3—C2111.97 (11)C1—O1—N1108.21 (10)
N1—C3—C3i119.03 (14)C4—O2—H2A109.5
C1—C2—C3—C3i179.69 (17)C3—N1—O1—C10.23 (14)
C1—C2—C3—N1−0.03 (15)C4—C1—C2—C3−179.05 (14)
C2—C1—C4—O2−13.3 (2)C4—C1—O1—N1179.11 (11)
C2—C1—O1—N1−0.26 (14)O1—C1—C2—C30.18 (14)
C2—C3—N1—O1−0.12 (15)O1—C1—C4—O2167.55 (11)
C3i—C3—N1—O1−179.87 (14)
D—H···AD—HH···AD···AD—H···A
O2—H2A···N1ii0.822.032.8461 (15)171
C10H12N2O6F(000) = 268
Mr = 256.22Dx = 1.597 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 4.5379 (4) ÅCell parameters from 3988 reflections
b = 9.9195 (8) Åθ = 2.7–32.1°
c = 12.0177 (9) ŵ = 0.13 mm1
β = 99.9312 (11)°T = 150 K
V = 532.86 (8) Å3Needle, colourless
Z = 20.49 × 0.20 × 0.11 mm
Bruker SMART APEXII CCD diffractometer1737 independent reflections
Radiation source: sealed tube1570 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.019
Detector resolution: 8.333 pixels mm-1θmax = 31.3°, θmin = 2.7°
φ and ω scansh = −6→6
Absorption correction: multi-scan (SADABS; Sheldrick, 2008)k = −14→14
Tmin = 0.904, Tmax = 0.985l = −17→17
7638 measured reflections
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.034Hydrogen site location: difference Fourier map
wR(F2) = 0.072All H-atom parameters refined
S = 1.00w = 1/[σ2(Fo2) + (0.010P)2 + 0.3955P] where P = (Fo2 + 2Fc2)/3
1737 reflections(Δ/σ)max < 0.001
106 parametersΔρmax = 0.44 e Å3
0 restraintsΔρmin = −0.22 e Å3
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.
xyzUiso*/Ueq
O10.58044 (17)0.58291 (7)0.30718 (6)0.01981 (16)
O20.23448 (16)0.42300 (8)0.13078 (6)0.01890 (15)
H2A0.174 (4)0.5035 (18)0.1182 (14)0.039 (4)*
O30.93528 (19)0.17777 (8)0.42532 (7)0.02252 (17)
H3A1.037 (4)0.1801 (18)0.4858 (16)0.045 (5)*
N10.7277 (2)0.60707 (9)0.41811 (7)0.02010 (18)
C10.6765 (2)0.46292 (10)0.27170 (8)0.01576 (17)
C20.8810 (2)0.40630 (9)0.35428 (8)0.01513 (17)
C30.9048 (2)0.50244 (10)0.44419 (8)0.01585 (18)
C40.5528 (2)0.42337 (10)0.15275 (8)0.01753 (18)
H4A0.631 (3)0.4856 (14)0.1016 (12)0.022 (3)*
H4B0.622 (3)0.3337 (14)0.1391 (11)0.021 (3)*
C51.0376 (2)0.27405 (10)0.35134 (9)0.01875 (19)
H5A1.255 (3)0.2866 (14)0.3717 (12)0.024 (3)*
H5B0.992 (3)0.2362 (14)0.2760 (11)0.021 (3)*
U11U22U33U12U13U23
O10.0240 (4)0.0166 (3)0.0163 (3)0.0036 (3)−0.0036 (3)−0.0010 (3)
O20.0163 (3)0.0169 (3)0.0216 (3)−0.0003 (3)−0.0019 (3)−0.0014 (3)
O30.0302 (4)0.0154 (3)0.0187 (4)−0.0019 (3)−0.0050 (3)0.0026 (3)
N10.0253 (4)0.0171 (4)0.0153 (4)0.0022 (3)−0.0038 (3)−0.0019 (3)
C10.0171 (4)0.0143 (4)0.0154 (4)−0.0012 (3)0.0015 (3)−0.0003 (3)
C20.0167 (4)0.0136 (4)0.0148 (4)−0.0008 (3)0.0017 (3)0.0001 (3)
C30.0183 (4)0.0139 (4)0.0145 (4)−0.0012 (3)0.0003 (3)0.0001 (3)
C40.0171 (4)0.0199 (4)0.0147 (4)−0.0007 (3)0.0001 (3)−0.0006 (3)
C50.0219 (4)0.0161 (4)0.0176 (4)0.0030 (3)0.0015 (3)−0.0006 (3)
O1—N11.4050 (11)C3—C21.4312 (13)
O2—H2A0.849 (18)C3—C3i1.4657 (18)
O2—C41.4229 (12)C4—C11.4952 (13)
O3—H3A0.792 (19)C4—H4A0.980 (14)
N1—C31.3171 (12)C4—H4B0.966 (14)
C1—O11.3612 (12)C5—O31.4354 (13)
C1—C21.3577 (13)C5—H5A0.982 (14)
C2—C51.4953 (13)C5—H5B0.969 (14)
C1—O1—N1108.71 (7)O2—C4—C1112.33 (8)
C4—O2—H2A108.4 (11)O2—C4—H4A110.6 (8)
C5—O3—H3A110.4 (13)O2—C4—H4B108.3 (8)
C3—N1—O1105.20 (8)C1—C4—H4A108.5 (8)
O1—C1—C4116.17 (8)C1—C4—H4B108.9 (8)
C2—C1—O1110.38 (8)H4A—C4—H4B108.1 (11)
C2—C1—C4133.38 (9)O3—C5—C2111.30 (8)
C1—C2—C3103.26 (8)O3—C5—H5A110.3 (8)
C1—C2—C5127.83 (9)O3—C5—H5B106.3 (8)
C3—C2—C5128.91 (9)C2—C5—H5A110.1 (8)
N1—C3—C2112.45 (8)C2—C5—H5B109.7 (8)
N1—C3—C3i118.88 (11)H5A—C5—H5B109.0 (11)
C2—C3—C3i128.67 (11)
O1—N1—C3—C2−0.53 (11)C1—C2—C5—O3−110.02 (11)
O1—N1—C3—C3i179.26 (10)C2—C1—O1—N10.05 (11)
O1—C1—C2—C3−0.35 (10)C3—C2—C5—O368.82 (13)
O1—C1—C2—C5178.72 (9)C3i—C3—C2—C1−179.21 (12)
O2—C4—C1—O1−54.93 (11)C3i—C3—C2—C51.74 (19)
O2—C4—C1—C2128.39 (11)C4—C1—O1—N1−177.38 (8)
N1—C3—C2—C10.56 (11)C4—C1—C2—C3176.48 (10)
N1—C3—C2—C5−178.49 (10)C4—C1—C2—C5−4.46 (18)
C1—O1—N1—C30.30 (10)
D—H···AD—HH···AD···AD—H···A
O2—H2A···O3ii0.849 (18)1.849 (18)2.6936 (11)172.8 (16)
O3—H3A···O2iii0.792 (19)2.085 (19)2.7898 (11)148.3 (18)
O3—H3A···N1i0.792 (19)2.550 (19)3.0728 (12)125.0 (16)
  9 in total

1.  A short history of SHELX.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr A       Date:  2007-12-21       Impact factor: 2.290

Review 2.  Isoxazole ring as a useful scaffold in a search for new therapeutic agents.

Authors:  Angelika Sysak; Bożena Obmińska-Mrukowicz
Journal:  Eur J Med Chem       Date:  2017-06-02       Impact factor: 6.514

3.  A click chemistry approach to 5,5'-disubstituted-3,3'-bisisoxazoles from dichloroglyoxime and alkynes: luminescent organometallic iridium and rhenium bisisoxazole complexes.

Authors:  Phillip L van der Peet; Timothy U Connell; Christian Gunawan; Jonathan M White; Paul S Donnelly; Spencer J Williams
Journal:  J Org Chem       Date:  2013-07-02       Impact factor: 4.354

4.  Crystallography Open Database - an open-access collection of crystal structures.

Authors:  Saulius Gražulis; Daniel Chateigner; Robert T Downs; A F T Yokochi; Miguel Quirós; Luca Lutterotti; Elena Manakova; Justas Butkus; Peter Moeck; Armel Le Bail
Journal:  J Appl Crystallogr       Date:  2009-05-30       Impact factor: 3.304

5.  SHELXT - integrated space-group and crystal-structure determination.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr A Found Adv       Date:  2015-01-01       Impact factor: 2.290

6.  Crystal structure refinement with SHELXL.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr C Struct Chem       Date:  2015-01-01       Impact factor: 1.172

7.  Structure validation in chemical crystallography.

Authors:  Anthony L Spek
Journal:  Acta Crystallogr D Biol Crystallogr       Date:  2009-01-20

8.  The anatomy of a comprehensive constrained, restrained refinement program for the modern computing environment - Olex2 dissected.

Authors:  Luc J Bourhis; Oleg V Dolomanov; Richard J Gildea; Judith A K Howard; Horst Puschmann
Journal:  Acta Crystallogr A Found Adv       Date:  2015-01-01       Impact factor: 2.290

9.  The Cambridge Structural Database.

Authors:  Colin R Groom; Ian J Bruno; Matthew P Lightfoot; Suzanna C Ward
Journal:  Acta Crystallogr B Struct Sci Cryst Eng Mater       Date:  2016-04-01
  9 in total

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