research communications
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
1-Methylimidazole 3-N-oxide (NMI-O) crystallizes as a monohydrate, C4H6N2O·H2O, in the monoclinic 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 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.
Keywords: crystal structure; catalysis; aryl N-oxides; 1-methyl-2H-imidazole 3-N-oxide; hydrate; hydrogen bonding.
CCDC reference: 1531714
1. Chemical context
Aryl-N-oxides are an important class of materials acting as highly efficient catalysts for the phosphorylation of (Murray et al., 2015) and also for the site-selective phosphoylation of polyols and (Murray et al. 2014). 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). 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) 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). 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) was the 1-methylimidazole semiperhydrate rather than NMI-O itself. We now present a simplified synthesis of MNI-O and the of its hydrate.
2. Structural commentary
The . 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.
of the title compound is shown in Fig. 13. 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 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, Fig. 2). The NMI-O⋯OH2⋯NMI-O⋯OH2⋯ chains are cross-linked in the by weaker C—H⋯O interactions (Table 1) with H⋯O contacts in the range 2.41–2.56 Å.
4. Database survey
A search of the Cambridge Structural Database (CSD, Version 5.37 update February 2016; Groom et al., 2016) for the imidazole-3-oxide 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). For 1-hydroxy-2,4,5-triphenyl-1H-imidazole 3-oxide (JADNAE; Sánchez-Migallón et al. 2003), the N+— O− bond length was particularly short at 1.276 and 1.278 Å for the two molecules in the 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). The previously reported synthesis also started from glyoxal but required eight steps (Laus et al., 2008). 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 . 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.
details are summarized in Table 2
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Supporting information
CCDC reference: 1531714
https://doi.org/10.1107/S2056989017002079/hb7643sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017002079/hb7643Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989017002079/hb7643Isup3.cml
Data collection: CrysAlis PRO (Rigaku OD, 2015); cell
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).C4H6N2O·H2O | F(000) = 248 |
Mr = 116.12 | Dx = 1.393 Mg m−3 |
Monoclinic, P21 | Cu Kα radiation, λ = 1.54184 Å |
a = 7.5941 (6) Å | Cell parameters from 1007 reflections |
b = 10.0703 (6) Å | θ = 6.3–74.8° |
c = 7.8286 (6) Å | µ = 0.95 mm−1 |
β = 112.402 (9)° | T = 100 K |
V = 553.51 (8) Å3 | Lath, colourless |
Z = 4 | 0.45 × 0.10 × 0.05 mm |
Rigaku SuperNova, Dualflex, AtlasS2 diffractometer | 1386 independent reflections |
Radiation source: fine-focus sealed X-ray tube, Enhance (Cu) X-ray Source | 1241 reflections with I > 2σ(I) |
Detector resolution: 5.2921 pixels mm-1 | Rint = 0.023 |
ω scans | θmax = 74.3°, θmin = 6.1° |
Absorption correction: multi-scan (CrysAlis PRO; Rigaku OD, 2015) | h = −9→8 |
Tmin = 0.419, Tmax = 1.000 | k = −12→5 |
2067 measured reflections | l = −9→7 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: mixed |
R[F2 > 2σ(F2)] = 0.042 | H 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 reflections | Δρmax = 0.21 e Å−3 |
163 parameters | Δρmin = −0.23 e Å−3 |
1 restraint |
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. |
x | y | z | Uiso*/Ueq | ||
O1A | 0.5193 (3) | 0.2133 (2) | 0.5360 (3) | 0.0218 (5) | |
N1A | 0.3842 (3) | 0.2757 (3) | 0.3934 (3) | 0.0176 (6) | |
N2A | 0.2057 (4) | 0.4269 (3) | 0.2161 (4) | 0.0189 (6) | |
C1A | 0.3553 (4) | 0.4046 (3) | 0.3747 (4) | 0.0193 (6) | |
H1A | 0.4276 | 0.4707 | 0.4589 | 0.023* | |
C2A | 0.2517 (4) | 0.2107 (3) | 0.2439 (4) | 0.0185 (6) | |
H2A | 0.2413 | 0.1176 | 0.2231 | 0.022* | |
C3A | 0.1392 (4) | 0.3066 (3) | 0.1325 (4) | 0.0185 (6) | |
H3A | 0.0348 | 0.2931 | 0.0187 | 0.022* | |
C4A | 0.1200 (4) | 0.5563 (3) | 0.1484 (5) | 0.0231 (7) | |
H4AA | 0.0184 | 0.5739 | 0.1936 | 0.035* | |
H4AB | 0.0667 | 0.5562 | 0.0130 | 0.035* | |
H4AC | 0.2176 | 0.6256 | 0.1934 | 0.035* | |
O2A | 0.7412 (3) | 0.3868 (2) | 0.8081 (3) | 0.0237 (5) | |
H2AA | 0.675 (7) | 0.410 (6) | 0.898 (7) | 0.063 (16)* | |
H2AB | 0.669 (6) | 0.335 (5) | 0.729 (6) | 0.039 (13)* | |
O1B | 0.5360 (3) | 0.4513 (2) | 1.0200 (3) | 0.0226 (5) | |
N1B | 0.3895 (4) | 0.5126 (3) | 0.8873 (3) | 0.0188 (6) | |
N2B | 0.2080 (4) | 0.6632 (3) | 0.7115 (4) | 0.0183 (6) | |
C1B | 0.3733 (4) | 0.6430 (3) | 0.8560 (4) | 0.0203 (7) | |
H1B | 0.4617 | 0.7092 | 0.9231 | 0.024* | |
C2B | 0.2336 (4) | 0.4478 (3) | 0.7620 (4) | 0.0201 (6) | |
H2B | 0.2105 | 0.3548 | 0.7544 | 0.024* | |
C3B | 0.1191 (4) | 0.5435 (3) | 0.6509 (4) | 0.0194 (6) | |
H3B | 0.0007 | 0.5300 | 0.5510 | 0.023* | |
C4B | 0.1431 (4) | 0.7915 (3) | 0.6217 (5) | 0.0222 (7) | |
H4BA | 0.1842 | 0.8624 | 0.7144 | 0.033* | |
H4BB | 0.0038 | 0.7916 | 0.5622 | 0.033* | |
H4BC | 0.1978 | 0.8065 | 0.5284 | 0.033* | |
O2B | 0.7272 (3) | 0.6268 (2) | 1.2987 (3) | 0.0242 (6) | |
H2BA | 0.663 (6) | 0.585 (5) | 1.205 (5) | 0.023 (10)* | |
H2BB | 0.638 (7) | 0.648 (6) | 1.351 (7) | 0.057 (15)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1A | 0.0226 (10) | 0.0189 (12) | 0.0202 (12) | 0.0033 (9) | 0.0039 (10) | 0.0048 (10) |
N1A | 0.0212 (12) | 0.0148 (13) | 0.0171 (12) | 0.0005 (9) | 0.0075 (10) | 0.0015 (10) |
N2A | 0.0236 (12) | 0.0108 (14) | 0.0229 (13) | 0.0007 (10) | 0.0095 (11) | 0.0008 (10) |
C1A | 0.0210 (13) | 0.0169 (16) | 0.0196 (15) | −0.0029 (12) | 0.0071 (12) | −0.0001 (11) |
C2A | 0.0228 (14) | 0.0103 (15) | 0.0223 (15) | −0.0013 (12) | 0.0084 (13) | −0.0007 (12) |
C3A | 0.0227 (14) | 0.0101 (14) | 0.0219 (15) | −0.0012 (11) | 0.0077 (12) | −0.0025 (12) |
C4A | 0.0290 (15) | 0.0107 (15) | 0.0300 (16) | 0.0013 (12) | 0.0117 (14) | 0.0027 (13) |
O2A | 0.0248 (11) | 0.0177 (13) | 0.0263 (12) | −0.0010 (9) | 0.0071 (10) | −0.0023 (10) |
O1B | 0.0256 (11) | 0.0192 (11) | 0.0185 (10) | 0.0039 (9) | 0.0032 (9) | −0.0010 (9) |
N1B | 0.0243 (13) | 0.0137 (14) | 0.0187 (13) | 0.0015 (10) | 0.0086 (11) | −0.0017 (9) |
N2B | 0.0229 (12) | 0.0110 (13) | 0.0220 (12) | 0.0005 (10) | 0.0097 (10) | −0.0001 (10) |
C1B | 0.0230 (15) | 0.0181 (16) | 0.0209 (14) | −0.0025 (12) | 0.0097 (13) | −0.0020 (12) |
C2B | 0.0263 (15) | 0.0111 (14) | 0.0224 (14) | −0.0015 (12) | 0.0087 (12) | −0.0012 (11) |
C3B | 0.0217 (13) | 0.0139 (15) | 0.0210 (13) | −0.0024 (12) | 0.0063 (12) | −0.0032 (12) |
C4B | 0.0280 (15) | 0.0108 (15) | 0.0279 (16) | 0.0015 (13) | 0.0107 (14) | 0.0025 (12) |
O2B | 0.0265 (12) | 0.0200 (14) | 0.0251 (11) | −0.0013 (10) | 0.0086 (10) | −0.0053 (10) |
O1A—N1A | 1.350 (3) | O1B—N1B | 1.348 (3) |
N1A—C1A | 1.315 (4) | N1B—C1B | 1.332 (4) |
N1A—C2A | 1.384 (4) | N1B—C2B | 1.380 (4) |
N2A—C1A | 1.344 (4) | N2B—C1B | 1.348 (4) |
N2A—C3A | 1.378 (4) | N2B—C3B | 1.374 (4) |
N2A—C4A | 1.463 (4) | N2B—C4B | 1.464 (4) |
C1A—H1A | 0.9500 | C1B—H1B | 0.9500 |
C2A—C3A | 1.362 (4) | C2B—C3B | 1.366 (4) |
C2A—H2A | 0.9500 | C2B—H2B | 0.9500 |
C3A—H3A | 0.9500 | C3B—H3B | 0.9500 |
C4A—H4AA | 0.9800 | C4B—H4BA | 0.9800 |
C4A—H4AB | 0.9800 | C4B—H4BB | 0.9800 |
C4A—H4AC | 0.9800 | C4B—H4BC | 0.9800 |
O2A—H2AA | 1.03 (6) | O2B—H2BA | 0.83 (4) |
O2A—H2AB | 0.83 (5) | O2B—H2BB | 0.94 (5) |
C1A—N1A—O1A | 126.5 (3) | C1B—N1B—O1B | 125.7 (3) |
C1A—N1A—C2A | 109.6 (3) | C1B—N1B—C2B | 110.0 (3) |
O1A—N1A—C2A | 123.9 (3) | O1B—N1B—C2B | 124.3 (3) |
C1A—N2A—C3A | 108.6 (3) | C1B—N2B—C3B | 109.6 (3) |
C1A—N2A—C4A | 125.8 (3) | C1B—N2B—C4B | 124.9 (3) |
C3A—N2A—C4A | 125.4 (3) | C3B—N2B—C4B | 125.3 (3) |
N1A—C1A—N2A | 108.3 (3) | N1B—C1B—N2B | 107.1 (3) |
N1A—C1A—H1A | 125.8 | N1B—C1B—H1B | 126.4 |
N2A—C1A—H1A | 125.8 | N2B—C1B—H1B | 126.4 |
C3A—C2A—N1A | 106.4 (3) | C3B—C2B—N1B | 106.5 (3) |
C3A—C2A—H2A | 126.8 | C3B—C2B—H2B | 126.7 |
N1A—C2A—H2A | 126.8 | N1B—C2B—H2B | 126.7 |
C2A—C3A—N2A | 107.0 (3) | C2B—C3B—N2B | 106.8 (3) |
C2A—C3A—H3A | 126.5 | C2B—C3B—H3B | 126.6 |
N2A—C3A—H3A | 126.5 | N2B—C3B—H3B | 126.6 |
N2A—C4A—H4AA | 109.5 | N2B—C4B—H4BA | 109.5 |
N2A—C4A—H4AB | 109.5 | N2B—C4B—H4BB | 109.5 |
H4AA—C4A—H4AB | 109.5 | H4BA—C4B—H4BB | 109.5 |
N2A—C4A—H4AC | 109.5 | N2B—C4B—H4BC | 109.5 |
H4AA—C4A—H4AC | 109.5 | H4BA—C4B—H4BC | 109.5 |
H4AB—C4A—H4AC | 109.5 | H4BB—C4B—H4BC | 109.5 |
H2AA—O2A—H2AB | 107 (4) | H2BA—O2B—H2BB | 103 (4) |
O1A—N1A—C1A—N2A | −178.9 (2) | O1B—N1B—C1B—N2B | 179.6 (2) |
C2A—N1A—C1A—N2A | 0.2 (3) | C2B—N1B—C1B—N2B | 0.0 (4) |
C3A—N2A—C1A—N1A | −0.1 (3) | C3B—N2B—C1B—N1B | 0.0 (3) |
C4A—N2A—C1A—N1A | 176.4 (3) | C4B—N2B—C1B—N1B | −174.4 (3) |
C1A—N1A—C2A—C3A | −0.2 (3) | C1B—N1B—C2B—C3B | 0.0 (4) |
O1A—N1A—C2A—C3A | 179.0 (2) | O1B—N1B—C2B—C3B | −179.6 (2) |
N1A—C2A—C3A—N2A | 0.1 (3) | N1B—C2B—C3B—N2B | 0.0 (3) |
C1A—N2A—C3A—C2A | 0.0 (3) | C1B—N2B—C3B—C2B | 0.0 (3) |
C4A—N2A—C3A—C2A | −176.6 (3) | C4B—N2B—C3B—C2B | 174.4 (3) |
D—H···A | D—H | H···A | D···A | 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+1/2, −z+2; (ii) −x+1, y+1/2, −z+1; (iii) −x+1, y−1/2, −z+2. |
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