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ISSN: 2056-9890

Crystal structure of 1-methylimidazole 3-oxide monohydrate

aWolfson Centre for Materials Processing, Brunel University London, Kingston Lane, Uxbridge, UB8 3PH, UK, and bDepartment of Chemistry, South Kensington Campus, Imperial College London, London, SW7 2AZ, UK
*Correspondence e-mail: chris.frampton@brunel.ac.uk

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 15 December 2016; accepted 8 February 2017; online 14 February 2017)

1-Methylimidazole 3-N-oxide (NMI-O) crystallizes as a monohydrate, C4H6N2O·H2O, in the monoclinic space group P21 with Z′ = 2 (mol­ecules A and B). The imidazole rings display a planar geometry (r.m.s. deviations = 0.0008 and 0.0002 Å) and are linked in the crystal structure into infinite zigzag strands of ⋯NMI-O(A)⋯OH2⋯NMI-O(B)⋯OH2⋯ units by O—H⋯O hydrogen bonds. These chains propagate along the b-axis direction of the unit cell.

1. Chemical context

Aryl-N-oxides are an important class of materials acting as highly efficient catalysts for the phospho­rylation of alcohols (Murray et al., 2015[Murray, J. I., Woscholski, R. & Spivey, A. C. (2015). Synlett, 26, 985-990.]) and also for the site-selective phos­phoyl­ation of polyols and peptides (Murray et al. 2014[Murray, J. I., Woscholski, R. & Spivey, A. C. (2014). Chem. Commun. 50, 13608-13611.]). One material in particular, 1-methylimidazole 3-N-oxide, (NMI-O), has been shown to be a highly efficient catalyst for both sulfonyl­ation and silylation procedures (Murray & Spivey, 2015[Murray, J. I. & Spivey, A. C. (2015). Adv. Synth. Catal. 357, 3825-3830.]). Until recently, NMI-O has been somewhat elusive in the literature. The synthesis of NMI-O and its use as a highly efficient catalyst for certain Morita–Baylis–Hillman reactions has been reported (Lin et al., 2005[Lin, Y.-S., Liu, C.-W. & Tsai, T. Y. R. (2005). Tetrahedron Lett. 46, 1859-1861.]) although no conclusive information on the structural identity of the material synthesized was presented. A recent paper, directed at the synthesis of salts of 1-alkyl-imidazole 3-oxides for use as ionic liquids also reported the synthesis of NMI-O, however all attempts at crystallizing a sample of this material were unsuccessful although two crystalline adducts of NMI-O, a tris (2-thien­yl)borane and a silver carbene hexa­fluorido­phosphate, were structurally characterized (Laus et al., 2008[Laus, G., Schwärtzler, A., Bentivoglioa, G., Hummel, M., Kahlenberg, V., Wurst, K., Kristeva, E., Schütz, J., Kopacka, H., Kreutz, C., Bonn, G., Andriyko, Y., Nauer, G. & Schottenberger, H. (2008). Z. Naturforsch. Teil B, 63, 447-464.]). These authors also demonstrated by NMR and subsequent X-ray structural analysis of a related 1,2-di­methyl­imidazole semiperhydrate material that the likely product reported earlier (Lin et al., 2005[Lin, Y.-S., Liu, C.-W. & Tsai, T. Y. R. (2005). Tetrahedron Lett. 46, 1859-1861.]) was the 1-methylimidazole semiperhydrate rather than NMI-O itself. We now present a simplified synthesis of MNI-O and the crystal structure of its hydrate.

[Scheme 1]

2. Structural commentary

The asymmetric unit of the title compound is shown in Fig. 1[link]. It contains two mol­ecules of NMI-O and two fully occupied and ordered water mol­ecules, making the overall stoichiometry a monohydrate. A calculated least-squares plane through the five atoms of the imidazole ring (C1, N1, C2, C3, N2) for mol­ecules A and B gave r.m.s. deviations from planarity of 0.0008 and 0.0002 Å, respectively, with the oxygen atoms of the N+— O groups also residing close to the ring plane; O1A, −0.021 (4) Å; O1B, −0.008 (4) Å. The methyl groups lie somewhat farther outside the plane of the ring with displacements of −0.073 (5) Å for C4A and −0.116 (1) Å for C4B. The dihedral angle formed between the least-squares planes of the A and B NMI-O mol­ecules is 12.96 (16)°. The present data were not of sufficient quality to determine the absolute structure.

[Figure 1]
Figure 1
View of the asymmetric unit of the title compound with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The O—H⋯O hydrogen bonds are shown as dashed lines.

3. Supra­molecular features

In the crystal, the NMI-O and water mol­ecules are linked by O—H⋯O hydrogen bonds to form an infinite NMI-O⋯OH2⋯NMI-O⋯OH2⋯ chain propagating along the b-axis direction of the unit cell. Each water mol­ecule forms two hydrogen bonds, one to each of the N+— O groups of NMI-O mol­ecules A and B with the oxygen atoms of these groups acting as double acceptors from both water mol­ecules (Table 1[link], Fig. 2[link]). The NMI-O⋯OH2⋯NMI-O⋯OH2⋯ chains are cross-linked in the crystal structure by weaker C—H⋯O inter­actions (Table 1[link]) with H⋯O contacts in the range 2.41–2.56 Å.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O2A—H2AA⋯O1B 1.03 (6) 1.73 (6) 2.752 (3) 172 (4)
O2A—H2AB⋯O1A 0.83 (5) 1.94 (5) 2.773 (3) 175 (4)
O2B—H2BA⋯O1B 0.83 (4) 1.94 (4) 2.752 (3) 167 (4)
O2B—H2BB⋯O1Ai 0.94 (5) 1.86 (5) 2.790 (3) 171 (5)
C1A—H1A⋯O1Aii 0.95 2.47 3.248 (4) 139
C4A—H4AC⋯O1Aii 0.98 2.46 3.308 (4) 145
C4B—H4BC⋯O1Aii 0.98 2.56 3.336 (4) 136
C1B—H1B⋯O1Bi 0.95 2.48 3.248 (4) 138
C2B—H2B⋯O2Biii 0.95 2.41 3.298 (4) 155
C4B—H4BA⋯O1Bi 0.98 2.50 3.345 (4) 144
Symmetry codes: (i) [-x+1, y+{\script{1\over 2}}, -z+2]; (ii) [-x+1, y+{\script{1\over 2}}, -z+1]; (iii) [-x+1, y-{\script{1\over 2}}, -z+2].
[Figure 2]
Figure 2
View of the crystal packing down the a axis. The O—H⋯O hydrogen bonds (see Table 1[link]) are shown as dotted lines.

4. Database survey

A search of the Cambridge Structural Database (CSD, Version 5.37 update February 2016; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) for the imidazole-3-oxide substructure yielded 16 hits, all of which were genuine examples of substituted imidazole-3-oxides. Closely related examples include 1-hy­droxy­imidazole-3-oxide (DOJKUJ), 1-hy­droxy-2-methyl­imidazole-3-oxide (DOJLAQ), 3-hy­droxy-1,2-di­methyl­imidazolium 1,2-di­meth­yl­imidazolium-3-oxide iodide (DOJMUL) and 1,2-di­methyl­imidazole-3-oxide (DOJNAS) (Laus et al., 2008[Laus, G., Schwärtzler, A., Bentivoglioa, G., Hummel, M., Kahlenberg, V., Wurst, K., Kristeva, E., Schütz, J., Kopacka, H., Kreutz, C., Bonn, G., Andriyko, Y., Nauer, G. & Schottenberger, H. (2008). Z. Naturforsch. Teil B, 63, 447-464.]). For 1-hy­droxy-2,4,5-triphenyl-1H-imidazole 3-oxide (JADNAE; Sánchez-Migallón et al. 2003[Sánchez-Migallón, A., de la Hoz, A., López, C., Claramunt, R. M., Infantes, L., Motherwell, S., Shankland, K., Nowell, H., Alkorta, I. & Elguero, J. (2003). Helv. Chim. Acta, 86, 1026-1039.]), the N+— O bond length was particularly short at 1.276 and 1.278 Å for the two mol­ecules in the asymmetric unit. For the title compound, the N+—O bond lengths are 1.350 (3) and 1.348 (3)Å for mol­ecules A and B, respectively. These values are within the range exhibited for the remaining 15 database entries (1.326–1.368 Å).

5. Synthesis and crystallization

The title compound was synthesized in a three-step, one-pot process in which aqueous glyoxal was condensed with hydroxyl­amine hydro­chloride in the presence of sodium carbonate to afford the mono-oxime. This inter­mediate was immediately condensed with methyl­amine to give the corres­ponding imine, which cyclo-condenses upon exposure to aqueous formaldehyde to give NMI-O after acidic workup in ∼68% yield (Murray & Spivey, 2016[Murray, J. I. & Spivey, A. C. (2016). Org. Synth. 93, 331-340.]). The previously reported synthesis also started from glyoxal but required eight steps (Laus et al., 2008[Laus, G., Schwärtzler, A., Bentivoglioa, G., Hummel, M., Kahlenberg, V., Wurst, K., Kristeva, E., Schütz, J., Kopacka, H., Kreutz, C., Bonn, G., Andriyko, Y., Nauer, G. & Schottenberger, H. (2008). Z. Naturforsch. Teil B, 63, 447-464.]). The material was concentrated in vacuo to afford a brown oil, which crystallized overnight as colourless laths in the freezer after exposure to air, forming a monohydrate species. The crystals as prepared were extremely hygroscopic, necessitating a rapid transfer to the cold stream of the diffractometer.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. The four water H atoms were located in a Fourier difference map and freely refined. All the remaining H atoms were placed geometrically in idealized positions and allowed to ride on their parent atoms: C—H = 0.95–0.98Å with Uiso(H) = 1.5Ueq(C-meth­yl) and Uiso(H) = 1.2Ueq(C) for other H atoms. The data were not of a sufficient quality to reliably determine the absolute structure.

Table 2
Experimental details

Crystal data
Chemical formula C4H6N2O·H2O
Mr 116.12
Crystal system, space group Monoclinic, P21
Temperature (K) 100
a, b, c (Å) 7.5941 (6), 10.0703 (6), 7.8286 (6)
β (°) 112.402 (9)
V3) 553.51 (8)
Z 4
Radiation type Cu Kα
μ (mm−1) 0.95
Crystal size (mm) 0.45 × 0.10 × 0.05
 
Data collection
Diffractometer Rigaku SuperNova, Dualflex, AtlasS2
Absorption correction Multi-scan (CrysAlis PRO; Rigaku OD, 2015[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Oxford, UK.])
Tmin, Tmax 0.419, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 2067, 1386, 1241
Rint 0.023
(sin θ/λ)max−1) 0.624
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.119, 1.01
No. of reflections 1386
No. of parameters 163
No. of restraints 1
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.21, −0.23
Computer programs: CrysAlis PRO (Rigaku OD, 2015[Rigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Oxford, UK.]), SHELXD2014 (Sheldrick et al., 2001[Sheldrick, G. M., Hauptman, H. A., Weeks, C. M., Miller, M. & Usón, I. (2001). International Tables for Crystallography, Vol. F, edited by E. Arnold & M. Rossmann, pp. 333-351. Dordrecht: Kluwer.]), SHELXL2014 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), 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.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2015); cell refinement: CrysAlis PRO (Rigaku OD, 2015); data reduction: CrysAlis PRO (Rigaku OD, 2015); program(s) used to solve structure: SHELXD2014 (Sheldrick et al., 2001); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: SHELXTL (Sheldrick, 2008) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008), Mercury (Macrae et al., 2008) and publCIF (Westrip, 2010).

1-Methylimidazole 3-N-oxide monohydrate top
Crystal data top
C4H6N2O·H2OF(000) = 248
Mr = 116.12Dx = 1.393 Mg m3
Monoclinic, P21Cu Kα radiation, λ = 1.54184 Å
a = 7.5941 (6) ÅCell parameters from 1007 reflections
b = 10.0703 (6) Åθ = 6.3–74.8°
c = 7.8286 (6) ŵ = 0.95 mm1
β = 112.402 (9)°T = 100 K
V = 553.51 (8) Å3Lath, colourless
Z = 40.45 × 0.10 × 0.05 mm
Data collection top
Rigaku SuperNova, Dualflex, AtlasS2
diffractometer
1386 independent reflections
Radiation source: fine-focus sealed X-ray tube, Enhance (Cu) X-ray Source1241 reflections with I > 2σ(I)
Detector resolution: 5.2921 pixels mm-1Rint = 0.023
ω scansθmax = 74.3°, θmin = 6.1°
Absorption correction: multi-scan
(CrysAlis PRO; Rigaku OD, 2015)
h = 98
Tmin = 0.419, Tmax = 1.000k = 125
2067 measured reflectionsl = 97
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.042H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.119 w = 1/[σ2(Fo2) + (0.075P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
1386 reflectionsΔρmax = 0.21 e Å3
163 parametersΔρmin = 0.23 e Å3
1 restraint
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
O1A0.5193 (3)0.2133 (2)0.5360 (3)0.0218 (5)
N1A0.3842 (3)0.2757 (3)0.3934 (3)0.0176 (6)
N2A0.2057 (4)0.4269 (3)0.2161 (4)0.0189 (6)
C1A0.3553 (4)0.4046 (3)0.3747 (4)0.0193 (6)
H1A0.42760.47070.45890.023*
C2A0.2517 (4)0.2107 (3)0.2439 (4)0.0185 (6)
H2A0.24130.11760.22310.022*
C3A0.1392 (4)0.3066 (3)0.1325 (4)0.0185 (6)
H3A0.03480.29310.01870.022*
C4A0.1200 (4)0.5563 (3)0.1484 (5)0.0231 (7)
H4AA0.01840.57390.19360.035*
H4AB0.06670.55620.01300.035*
H4AC0.21760.62560.19340.035*
O2A0.7412 (3)0.3868 (2)0.8081 (3)0.0237 (5)
H2AA0.675 (7)0.410 (6)0.898 (7)0.063 (16)*
H2AB0.669 (6)0.335 (5)0.729 (6)0.039 (13)*
O1B0.5360 (3)0.4513 (2)1.0200 (3)0.0226 (5)
N1B0.3895 (4)0.5126 (3)0.8873 (3)0.0188 (6)
N2B0.2080 (4)0.6632 (3)0.7115 (4)0.0183 (6)
C1B0.3733 (4)0.6430 (3)0.8560 (4)0.0203 (7)
H1B0.46170.70920.92310.024*
C2B0.2336 (4)0.4478 (3)0.7620 (4)0.0201 (6)
H2B0.21050.35480.75440.024*
C3B0.1191 (4)0.5435 (3)0.6509 (4)0.0194 (6)
H3B0.00070.53000.55100.023*
C4B0.1431 (4)0.7915 (3)0.6217 (5)0.0222 (7)
H4BA0.18420.86240.71440.033*
H4BB0.00380.79160.56220.033*
H4BC0.19780.80650.52840.033*
O2B0.7272 (3)0.6268 (2)1.2987 (3)0.0242 (6)
H2BA0.663 (6)0.585 (5)1.205 (5)0.023 (10)*
H2BB0.638 (7)0.648 (6)1.351 (7)0.057 (15)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O1A0.0226 (10)0.0189 (12)0.0202 (12)0.0033 (9)0.0039 (10)0.0048 (10)
N1A0.0212 (12)0.0148 (13)0.0171 (12)0.0005 (9)0.0075 (10)0.0015 (10)
N2A0.0236 (12)0.0108 (14)0.0229 (13)0.0007 (10)0.0095 (11)0.0008 (10)
C1A0.0210 (13)0.0169 (16)0.0196 (15)0.0029 (12)0.0071 (12)0.0001 (11)
C2A0.0228 (14)0.0103 (15)0.0223 (15)0.0013 (12)0.0084 (13)0.0007 (12)
C3A0.0227 (14)0.0101 (14)0.0219 (15)0.0012 (11)0.0077 (12)0.0025 (12)
C4A0.0290 (15)0.0107 (15)0.0300 (16)0.0013 (12)0.0117 (14)0.0027 (13)
O2A0.0248 (11)0.0177 (13)0.0263 (12)0.0010 (9)0.0071 (10)0.0023 (10)
O1B0.0256 (11)0.0192 (11)0.0185 (10)0.0039 (9)0.0032 (9)0.0010 (9)
N1B0.0243 (13)0.0137 (14)0.0187 (13)0.0015 (10)0.0086 (11)0.0017 (9)
N2B0.0229 (12)0.0110 (13)0.0220 (12)0.0005 (10)0.0097 (10)0.0001 (10)
C1B0.0230 (15)0.0181 (16)0.0209 (14)0.0025 (12)0.0097 (13)0.0020 (12)
C2B0.0263 (15)0.0111 (14)0.0224 (14)0.0015 (12)0.0087 (12)0.0012 (11)
C3B0.0217 (13)0.0139 (15)0.0210 (13)0.0024 (12)0.0063 (12)0.0032 (12)
C4B0.0280 (15)0.0108 (15)0.0279 (16)0.0015 (13)0.0107 (14)0.0025 (12)
O2B0.0265 (12)0.0200 (14)0.0251 (11)0.0013 (10)0.0086 (10)0.0053 (10)
Geometric parameters (Å, º) top
O1A—N1A1.350 (3)O1B—N1B1.348 (3)
N1A—C1A1.315 (4)N1B—C1B1.332 (4)
N1A—C2A1.384 (4)N1B—C2B1.380 (4)
N2A—C1A1.344 (4)N2B—C1B1.348 (4)
N2A—C3A1.378 (4)N2B—C3B1.374 (4)
N2A—C4A1.463 (4)N2B—C4B1.464 (4)
C1A—H1A0.9500C1B—H1B0.9500
C2A—C3A1.362 (4)C2B—C3B1.366 (4)
C2A—H2A0.9500C2B—H2B0.9500
C3A—H3A0.9500C3B—H3B0.9500
C4A—H4AA0.9800C4B—H4BA0.9800
C4A—H4AB0.9800C4B—H4BB0.9800
C4A—H4AC0.9800C4B—H4BC0.9800
O2A—H2AA1.03 (6)O2B—H2BA0.83 (4)
O2A—H2AB0.83 (5)O2B—H2BB0.94 (5)
C1A—N1A—O1A126.5 (3)C1B—N1B—O1B125.7 (3)
C1A—N1A—C2A109.6 (3)C1B—N1B—C2B110.0 (3)
O1A—N1A—C2A123.9 (3)O1B—N1B—C2B124.3 (3)
C1A—N2A—C3A108.6 (3)C1B—N2B—C3B109.6 (3)
C1A—N2A—C4A125.8 (3)C1B—N2B—C4B124.9 (3)
C3A—N2A—C4A125.4 (3)C3B—N2B—C4B125.3 (3)
N1A—C1A—N2A108.3 (3)N1B—C1B—N2B107.1 (3)
N1A—C1A—H1A125.8N1B—C1B—H1B126.4
N2A—C1A—H1A125.8N2B—C1B—H1B126.4
C3A—C2A—N1A106.4 (3)C3B—C2B—N1B106.5 (3)
C3A—C2A—H2A126.8C3B—C2B—H2B126.7
N1A—C2A—H2A126.8N1B—C2B—H2B126.7
C2A—C3A—N2A107.0 (3)C2B—C3B—N2B106.8 (3)
C2A—C3A—H3A126.5C2B—C3B—H3B126.6
N2A—C3A—H3A126.5N2B—C3B—H3B126.6
N2A—C4A—H4AA109.5N2B—C4B—H4BA109.5
N2A—C4A—H4AB109.5N2B—C4B—H4BB109.5
H4AA—C4A—H4AB109.5H4BA—C4B—H4BB109.5
N2A—C4A—H4AC109.5N2B—C4B—H4BC109.5
H4AA—C4A—H4AC109.5H4BA—C4B—H4BC109.5
H4AB—C4A—H4AC109.5H4BB—C4B—H4BC109.5
H2AA—O2A—H2AB107 (4)H2BA—O2B—H2BB103 (4)
O1A—N1A—C1A—N2A178.9 (2)O1B—N1B—C1B—N2B179.6 (2)
C2A—N1A—C1A—N2A0.2 (3)C2B—N1B—C1B—N2B0.0 (4)
C3A—N2A—C1A—N1A0.1 (3)C3B—N2B—C1B—N1B0.0 (3)
C4A—N2A—C1A—N1A176.4 (3)C4B—N2B—C1B—N1B174.4 (3)
C1A—N1A—C2A—C3A0.2 (3)C1B—N1B—C2B—C3B0.0 (4)
O1A—N1A—C2A—C3A179.0 (2)O1B—N1B—C2B—C3B179.6 (2)
N1A—C2A—C3A—N2A0.1 (3)N1B—C2B—C3B—N2B0.0 (3)
C1A—N2A—C3A—C2A0.0 (3)C1B—N2B—C3B—C2B0.0 (3)
C4A—N2A—C3A—C2A176.6 (3)C4B—N2B—C3B—C2B174.4 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2A—H2AA···O1B1.03 (6)1.73 (6)2.752 (3)172 (4)
O2A—H2AB···O1A0.83 (5)1.94 (5)2.773 (3)175 (4)
O2B—H2BA···O1B0.83 (4)1.94 (4)2.752 (3)167 (4)
O2B—H2BB···O1Ai0.94 (5)1.86 (5)2.790 (3)171 (5)
C1A—H1A···O1Aii0.952.473.248 (4)139
C4A—H4AC···O1Aii0.982.463.308 (4)145
C4B—H4BC···O1Aii0.982.563.336 (4)136
C1B—H1B···O1Bi0.952.483.248 (4)138
C2B—H2B···O2Biii0.952.413.298 (4)155
C4B—H4BA···O1Bi0.982.503.345 (4)144
Symmetry codes: (i) x+1, y+1/2, z+2; (ii) x+1, y+1/2, z+1; (iii) x+1, y1/2, z+2.
 

References

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 citationLaus, G., Schwärtzler, A., Bentivoglioa, G., Hummel, M., Kahlenberg, V., Wurst, K., Kristeva, E., Schütz, J., Kopacka, H., Kreutz, C., Bonn, G., Andriyko, Y., Nauer, G. & Schottenberger, H. (2008). Z. Naturforsch. Teil B, 63, 447–464.  CAS Google Scholar
First citationLin, Y.-S., Liu, C.-W. & Tsai, T. Y. R. (2005). Tetrahedron Lett. 46, 1859–1861.  Web of Science 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 citationMurray, J. I. & Spivey, A. C. (2016). Org. Synth. 93, 331–340.  Web of Science CrossRef CAS Google Scholar
First citationMurray, J. I. & Spivey, A. C. (2015). Adv. Synth. Catal. 357, 3825–3830.  Web of Science CrossRef CAS Google Scholar
First citationMurray, J. I., Woscholski, R. & Spivey, A. C. (2014). Chem. Commun. 50, 13608–13611.  Web of Science CrossRef CAS Google Scholar
First citationMurray, J. I., Woscholski, R. & Spivey, A. C. (2015). Synlett, 26, 985–990.  CAS Google Scholar
First citationRigaku OD (2015). CrysAlis PRO. Rigaku Oxford Diffraction, Oxford, UK.  Google Scholar
First citationSánchez-Migallón, A., de la Hoz, A., López, C., Claramunt, R. M., Infantes, L., Motherwell, S., Shankland, K., Nowell, H., Alkorta, I. & Elguero, J. (2003). Helv. Chim. Acta, 86, 1026–1039.  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. (2015). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M., Hauptman, H. A., Weeks, C. M., Miller, M. & Usón, I. (2001). International Tables for Crystallography, Vol. F, edited by E. Arnold & M. Rossmann, pp. 333–351. Dordrecht: Kluwer.  Google Scholar
First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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