organic compounds
[3-Methoxy-5-(methoxycarbonyl)isoxazol-4-yl](4-methoxyphenyl)iodonium 2,2,2-trifluoroacetate
aFaculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia, and bEaStCHEM School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, United Kingdom
*Correspondence e-mail: abdfatah@uitm.edu.my
A new isoxazole-based iodonoium salt, C13H13INO5+·C2F3O2−, has been synthesized and structurally characterized. In the crystal, ions are linked by short I⋯O contacts to form a neutral tetra-ion aggregate. These combine with C—H⋯F and C—H⋯O interactions to form double-layered two-dimensional sheets in the (001) plane.
Keywords: crystal structure; isoxazole; 4-methoxyphenyl; iodonium; dimer.
CCDC reference: 2253285
Structure description
Hypervalent iodine compounds exhibit attractive features of low cost, mild and selective reagents in organic synthesis (Wirth, 2005; Richardson & Wirth, 2006). These reagents serve as environmentally benign alternatives to toxic heavy-metal-based oxidants and expensive organometallic catalysts (Satam et al., 2010; Wirth, 2001). The application of iodonium reagents in organic transformation encompasses areas such as C—C, C–heteroatom and heteroatom–heteroatom bond formation, oxidations, rearrangements and radical reactions (Frigerio & Santagostino, 1994; Zhdankin & Stang, 2008; Zhdankin, 2009, 2011).
A particularly important application is the reaction of diaryliodonium salts with fluorine anions, allowing the introduction of fluorine into chemical compounds of interest (Tredwell & Gouverneur 2012; Tredwell et al., 2008). Furthermore, by using diaryliodonium salts, both electron-deficient and electron-rich rings can be fluorinated, allowing access to all regioisomers of a particular arene over standard SNAr chemistry (Shah et al., 1998). Moreover, these types of reaction typically require milder conditions than standard SNAr reactions, and they can even take place in wet solvents (Chun et al., 2013). Features which are privileged for the incorporation of radioactive [18F]-fluoride into radiotracer molecules established for Positron Emission Tomography.
The versatility of isoxazoles core components in biologically active compounds, natural products and functional materials (Abdul Manan et al., 2017; Frolund et al., 2002; Lee et al., 2009) led us to examine the synthesis of iodonoum salts bearing an isoxazole motif possessing novel structural features with the possibly of some interest as a precursor to fluoroisoxazole.
The title salt, C13H13INO5+·C2F3O2−, crystallizes in the P with one in the asymmetric-unit (Fig. 1). In the crystal, the ring of the isoxazole group is inclined to the methoxyphenyl ring at an angle of 84.4 (3)° and the C—I—C bond angle is 90.8 (3)°. Short I⋯O contacts of 2.555 (6) and 2.823 (7) Å are observed due to the strong electrostatic interaction between two iodonium cations and two trifluoroacetate counter-ions (Fig. 2). There are also C—H⋯F and C—H⋯O interactions present (Table 1). The C—H⋯O interactions give rise to two-dimensional sheets in the (001) plane, with the C—H⋯F interactions holding the trifluoroacetate anion in place within the sheets (Fig. 3). The combination of the weak hydrogen bonds with the I⋯O interactions gives rise to double-layered sheets, also in the (001) plane. These interactions are comparable to those observed in phenyl(phenylethynyl)iodonium tosylate and phenyl(phenylethynyl)iodonium trifluoroacetate salts (Dixon et al., 2013).
Synthesis and crystallization
m-CPBA (70% active oxidant, 791 mg, 3.21 mmol, 1.3 eq.) was added to a solution of methyl 4-iodo-3-methoxyisoxazole-5-carboxylate (700 mg, 2.47 mmol, 1.0 eq.) in AcOH (20 ml). After stirring at 55°C for 96 h, water (30 ml) was added to the reaction mixture followed by extraction into DCM (3 × 20 ml). The combined organic layers were washed with a saturated aqueous solution of Na2CO3 (60 ml), dried over Na2SO4, filtered and concentrated under reduced pressure to afford a colourless solid, which was used without further purification.
Methyl (4-diacetoxyiodo)-3-methoxyisoxazole-5-carboxylate (281 mg, 0.7 mmol, 1.0 eq.), as a 40% mixture determined by 1H-NMR, with methyl 4-iodo-3-methoxyisoxazole-5-carboxylate, was dissolved in DCM (10 ml) and cooled to −30°C, followed by dropwise addition of TFA (110 ml, 1.40 mmol, 2.0 eq.). The solution was stirred with the exclusion of light for 30 min, followed by 1 h at rt. The reaction mixture was re-cooled to −30°C and tributyl(4-methoxyphenyl)stannane (278 mg, 0.70 mmol, 1.0 eq.) added. The reaction was warmed to rt for the second time and left to stir overnight. The solvent was removed in vacuo. Upon the addition of Et2O, the (3-methoxy-5-(methoxycarbonyl)isoxazol-4-yl)(4-methoxyphenyl)iodonium TFA salt (35 mg, 10%) crystallized. Crystals suitable for X-ray were obtained from the diffusion of diethyl ether into a dichloromethane solution of the title compound.
1H (500 MHz, d6-DMSO), δ: (p.p.m): 8.00 (2H, d, 3JHH 7.2), 7.06 (2H, d, 3JHH 7.2), 4.07 (3H, s), 4.01 (3H, s), 3.80 (3H, s); 13C (125 MHz, d6-DMSO), δ: (p.p.m): 170.1, 162.0, 161.0, 155.3, 137.0, 117.5, 107.0, 83.9, 59.0, 55.7, 54.0; 19F (470 MHz, d6-DMSO), δ: (p.p.m): −73.6 (3 F, s); HRMS m/z (ESI+), [M − TFA]+ calculated (C13H13NO5127I) 389.9833, found 389.9819.
Refinement
Crystal data, data collection and structure . The maximum residual electron density peak of 1.48 e Å−3 was located 1.01 Å from the I4 atom.
details are summarized in Table 2Structural data
CCDC reference: 2253285
https://doi.org/10.1107/S2414314623003000/tk4090sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314623003000/tk4090Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2414314623003000/tk4090Isup3.mol
Supporting information file. DOI: https://doi.org/10.1107/S2414314623003000/tk4090Isup4.cml
Data collection: CrystalClear (Rigaku, 2014); cell
CrystalClear (Rigaku, 2014); data reduction: CrystalClear (Rigaku, 2014); program(s) used to solve structure: DIRDIF99 (Beurskens et al., 1999); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: Olex2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2020); software used to prepare material for publication: CrystalStructure (Rigaku, 2018), enCIFer (Allen et al., 2004) and publCIF (Westrip, 2010).C13H13INO5+·C2F3O2− | Z = 2 |
Mr = 503.17 | F(000) = 492.00 |
Triclinic, P1 | Dx = 1.842 Mg m−3 |
a = 8.436 (2) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 10.750 (3) Å | Cell parameters from 1722 reflections |
c = 11.338 (3) Å | θ = 2.0–25.3° |
α = 113.913 (5)° | µ = 1.83 mm−1 |
β = 97.392 (4)° | T = 173 K |
γ = 98.975 (5)° | Plate, colourless |
V = 907.2 (4) Å3 | 0.16 × 0.03 × 0.01 mm |
Rigaku XtaLAB P200 diffractometer | 3270 independent reflections |
Radiation source: Rotating Anode, Rigaku FR-X | 2423 reflections with F2 > 2.0σ(F2) |
Rigaku Osmic Confocal Optical System monochromator | Rint = 0.053 |
Detector resolution: 5.814 pixels mm-1 | θmax = 25.4°, θmin = 2.0° |
ω scans | h = −10→10 |
Absorption correction: multi-scan (CrystalClear; Rigaku, 2014) | k = −12→12 |
Tmin = 0.862, Tmax = 0.982 | l = −13→13 |
11079 measured reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.060 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.145 | H-atom parameters constrained |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0635P)2 + 4.1326P] where P = (Fo2 + 2Fc2)/3 |
3270 reflections | (Δ/σ)max < 0.001 |
246 parameters | Δρmax = 1.49 e Å−3 |
0 restraints | Δρmin = −0.65 e Å−3 |
Primary atom site location: structure-invariant direct methods |
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. |
Refinement. Carbon-bound H atoms were included in calculated positions (C—H = 0.95–0.98 Å) and refined as riding atoms with Uiso(H) = 1.2Ueq (sp2) or Uiso(H) = 1.5Ueq (sp3). |
x | y | z | Uiso*/Ueq | ||
I4 | 0.20970 (6) | 0.42981 (5) | 0.12013 (5) | 0.0509 (2) | |
F16 | 0.2459 (9) | 0.9270 (9) | 0.2807 (8) | 0.152 (4) | |
F17 | 0.0378 (8) | 0.9854 (6) | 0.3427 (6) | 0.111 (3) | |
F18 | 0.1490 (12) | 0.8548 (8) | 0.4008 (6) | 0.136 (3) | |
O1 | 0.4332 (8) | 0.6834 (6) | 0.5238 (5) | 0.0632 (16) | |
O3 | 0.5054 (8) | 0.7371 (7) | 0.2570 (7) | 0.0717 (18) | |
O6 | 0.1162 (9) | 0.3812 (7) | 0.3838 (7) | 0.0777 (19) | |
O7 | 0.2682 (9) | 0.4996 (8) | 0.5853 (7) | 0.081 (2) | |
O12 | 0.7116 (10) | 0.0695 (8) | 0.1381 (8) | 0.094 (2) | |
O17 | −0.0913 (8) | 0.7775 (6) | 0.1053 (6) | 0.076 (2) | |
O18 | 0.0342 (9) | 0.6423 (7) | 0.1656 (7) | 0.086 (2) | |
N2 | 0.5171 (10) | 0.7647 (9) | 0.4715 (8) | 0.074 (2) | |
C3 | 0.4577 (11) | 0.6993 (9) | 0.3442 (9) | 0.061 (3) | |
C4 | 0.3342 (10) | 0.5742 (9) | 0.3109 (8) | 0.057 (2) | |
C5 | 0.3256 (11) | 0.5714 (10) | 0.4265 (9) | 0.064 (2) | |
C6 | 0.2232 (12) | 0.4716 (11) | 0.4574 (9) | 0.064 (3) | |
C7 | 0.1665 (14) | 0.4074 (13) | 0.6255 (13) | 0.095 (4) | |
H7A | 0.165550 | 0.309983 | 0.568918 | 0.143* | |
H7B | 0.054106 | 0.421058 | 0.616962 | 0.143* | |
H7C | 0.211381 | 0.429339 | 0.717581 | 0.143* | |
C8 | 0.6252 (12) | 0.8788 (11) | 0.3162 (11) | 0.084 (3) | |
H8A | 0.723922 | 0.876368 | 0.370487 | 0.126* | |
H8B | 0.573436 | 0.950570 | 0.371279 | 0.126* | |
H8C | 0.655593 | 0.900916 | 0.245180 | 0.126* | |
C9 | 0.3799 (11) | 0.3064 (9) | 0.1113 (8) | 0.055 (2) | |
C10 | 0.3599 (15) | 0.2162 (11) | 0.1705 (9) | 0.080 (3) | |
H10 | 0.267985 | 0.210169 | 0.209962 | 0.096* | |
C11 | 0.4686 (15) | 0.1368 (12) | 0.1732 (10) | 0.083 (3) | |
H11 | 0.447999 | 0.068052 | 0.205282 | 0.099* | |
C12 | 0.5986 (13) | 0.1563 (11) | 0.1318 (11) | 0.070 (3) | |
C13 | 0.6360 (12) | 0.2401 (12) | 0.0699 (11) | 0.090 (4) | |
H13 | 0.733464 | 0.245200 | 0.036741 | 0.108* | |
C14 | 0.5113 (13) | 0.3240 (11) | 0.0579 (10) | 0.077 (3) | |
H14 | 0.524458 | 0.384409 | 0.015910 | 0.093* | |
C15 | 0.8561 (13) | 0.1021 (16) | 0.1053 (14) | 0.137 (7) | |
H15A | 0.925082 | 0.038937 | 0.112025 | 0.206* | |
H15B | 0.835017 | 0.092238 | 0.014517 | 0.206* | |
H15C | 0.912545 | 0.198818 | 0.165580 | 0.206* | |
C16 | 0.1083 (10) | 0.8821 (9) | 0.3002 (8) | 0.056 (2) | |
C17 | 0.0083 (9) | 0.7542 (9) | 0.1774 (8) | 0.049 (2) |
U11 | U22 | U33 | U12 | U13 | U23 | |
I4 | 0.0529 (4) | 0.0449 (3) | 0.0430 (3) | 0.0166 (2) | −0.0062 (2) | 0.0102 (2) |
F16 | 0.085 (5) | 0.135 (7) | 0.130 (7) | −0.041 (5) | 0.028 (5) | −0.023 (5) |
F17 | 0.099 (5) | 0.068 (4) | 0.098 (5) | 0.038 (4) | −0.031 (4) | −0.021 (3) |
F18 | 0.212 (9) | 0.098 (5) | 0.057 (4) | 0.025 (5) | −0.042 (5) | 0.017 (4) |
O1 | 0.067 (4) | 0.062 (4) | 0.040 (3) | 0.014 (3) | −0.004 (3) | 0.007 (3) |
O3 | 0.069 (4) | 0.068 (4) | 0.077 (5) | 0.009 (3) | 0.009 (4) | 0.035 (4) |
O6 | 0.075 (5) | 0.071 (5) | 0.073 (4) | −0.005 (4) | 0.003 (4) | 0.029 (4) |
O7 | 0.080 (5) | 0.101 (5) | 0.063 (4) | 0.023 (4) | 0.009 (4) | 0.037 (4) |
O12 | 0.105 (6) | 0.095 (6) | 0.093 (5) | 0.038 (5) | 0.019 (5) | 0.047 (5) |
O17 | 0.089 (5) | 0.054 (4) | 0.060 (4) | 0.020 (3) | −0.024 (3) | 0.011 (3) |
O18 | 0.096 (5) | 0.057 (4) | 0.083 (5) | 0.032 (4) | −0.019 (4) | 0.013 (4) |
N2 | 0.070 (5) | 0.067 (5) | 0.068 (5) | 0.006 (4) | −0.002 (4) | 0.019 (5) |
C3 | 0.052 (5) | 0.046 (5) | 0.054 (5) | 0.012 (4) | −0.015 (4) | −0.002 (4) |
C4 | 0.057 (5) | 0.060 (6) | 0.045 (5) | 0.027 (5) | 0.000 (4) | 0.011 (4) |
C5 | 0.056 (5) | 0.065 (6) | 0.055 (5) | 0.019 (5) | 0.002 (4) | 0.013 (5) |
C6 | 0.058 (6) | 0.069 (7) | 0.057 (6) | 0.027 (5) | −0.002 (5) | 0.021 (5) |
C7 | 0.078 (8) | 0.118 (10) | 0.118 (10) | 0.029 (7) | 0.036 (7) | 0.073 (9) |
C8 | 0.065 (6) | 0.067 (7) | 0.091 (8) | −0.002 (5) | −0.010 (5) | 0.020 (6) |
C9 | 0.059 (5) | 0.051 (5) | 0.043 (4) | 0.023 (4) | −0.006 (4) | 0.010 (4) |
C10 | 0.115 (9) | 0.073 (7) | 0.051 (5) | 0.054 (6) | 0.009 (5) | 0.016 (5) |
C11 | 0.099 (9) | 0.090 (8) | 0.062 (6) | 0.044 (7) | 0.016 (6) | 0.028 (6) |
C12 | 0.057 (6) | 0.083 (7) | 0.079 (7) | 0.012 (5) | 0.002 (5) | 0.051 (6) |
C13 | 0.055 (6) | 0.083 (8) | 0.078 (7) | 0.000 (6) | 0.025 (5) | −0.015 (6) |
C14 | 0.074 (7) | 0.060 (6) | 0.079 (7) | 0.014 (5) | 0.025 (6) | 0.010 (5) |
C15 | 0.042 (6) | 0.154 (13) | 0.122 (11) | −0.036 (7) | 0.039 (7) | −0.018 (9) |
C16 | 0.043 (5) | 0.057 (6) | 0.051 (5) | 0.008 (4) | −0.003 (4) | 0.013 (4) |
C17 | 0.043 (4) | 0.048 (5) | 0.047 (5) | 0.018 (4) | 0.005 (4) | 0.012 (4) |
I4—C9 | 2.087 (8) | C7—H7A | 0.9800 |
I4—C4 | 2.092 (8) | C7—H7B | 0.9800 |
F16—C16 | 1.268 (11) | C7—H7C | 0.9800 |
F17—C16 | 1.290 (10) | C8—H8A | 0.9800 |
F18—C16 | 1.307 (11) | C8—H8B | 0.9800 |
O1—C5 | 1.347 (10) | C8—H8C | 0.9800 |
O1—N2 | 1.397 (10) | C9—C14 | 1.353 (13) |
O3—C3 | 1.297 (12) | C9—C10 | 1.388 (14) |
O3—C8 | 1.520 (11) | C10—C11 | 1.353 (14) |
O6—C6 | 1.154 (11) | C10—H10 | 0.9500 |
O7—C6 | 1.344 (11) | C11—C12 | 1.268 (15) |
O7—C7 | 1.459 (13) | C11—H11 | 0.9500 |
O12—C15 | 1.355 (12) | C12—C13 | 1.374 (15) |
O12—C12 | 1.449 (12) | C13—C14 | 1.515 (16) |
O17—C17 | 1.221 (9) | C13—H13 | 0.9500 |
O18—C17 | 1.214 (10) | C14—H14 | 0.9500 |
N2—C3 | 1.308 (12) | C15—H15A | 0.9800 |
C3—C4 | 1.445 (13) | C15—H15B | 0.9800 |
C4—C5 | 1.334 (13) | C15—H15C | 0.9800 |
C5—C6 | 1.453 (14) | C16—C17 | 1.524 (11) |
C9—I4—C4 | 90.8 (3) | C10—C9—I4 | 117.9 (7) |
C5—O1—N2 | 110.3 (7) | C11—C10—C9 | 121.3 (11) |
C3—O3—C8 | 113.8 (8) | C11—C10—H10 | 119.3 |
C6—O7—C7 | 114.1 (9) | C9—C10—H10 | 119.3 |
C15—O12—C12 | 114.6 (11) | C12—C11—C10 | 118.4 (12) |
C3—N2—O1 | 104.8 (8) | C12—C11—H11 | 120.8 |
O3—C3—N2 | 125.4 (9) | C10—C11—H11 | 120.8 |
O3—C3—C4 | 123.4 (8) | C11—C12—C13 | 127.0 (11) |
N2—C3—C4 | 111.1 (10) | C11—C12—O12 | 116.1 (10) |
C5—C4—C3 | 104.5 (8) | C13—C12—O12 | 116.5 (10) |
C5—C4—I4 | 129.6 (8) | C12—C13—C14 | 115.5 (9) |
C3—C4—I4 | 125.8 (7) | C12—C13—H13 | 122.2 |
C4—C5—O1 | 109.2 (9) | C14—C13—H13 | 122.2 |
C4—C5—C6 | 130.6 (9) | C9—C14—C13 | 115.1 (10) |
O1—C5—C6 | 120.2 (9) | C9—C14—H14 | 122.5 |
O6—C6—O7 | 123.9 (10) | C13—C14—H14 | 122.5 |
O6—C6—C5 | 125.4 (9) | O12—C15—H15A | 109.5 |
O7—C6—C5 | 110.8 (9) | O12—C15—H15B | 109.5 |
O7—C7—H7A | 109.5 | H15A—C15—H15B | 109.5 |
O7—C7—H7B | 109.5 | O12—C15—H15C | 109.5 |
H7A—C7—H7B | 109.5 | H15A—C15—H15C | 109.5 |
O7—C7—H7C | 109.5 | H15B—C15—H15C | 109.5 |
H7A—C7—H7C | 109.5 | F16—C16—F17 | 107.8 (9) |
H7B—C7—H7C | 109.5 | F16—C16—F18 | 103.2 (9) |
O3—C8—H8A | 109.5 | F17—C16—F18 | 105.7 (8) |
O3—C8—H8B | 109.5 | F16—C16—C17 | 110.8 (8) |
H8A—C8—H8B | 109.5 | F17—C16—C17 | 115.2 (7) |
O3—C8—H8C | 109.5 | F18—C16—C17 | 113.2 (8) |
H8A—C8—H8C | 109.5 | O18—C17—O17 | 128.3 (8) |
H8B—C8—H8C | 109.5 | O18—C17—C16 | 116.1 (7) |
C14—C9—C10 | 122.3 (9) | O17—C17—C16 | 115.6 (7) |
C14—C9—I4 | 119.7 (7) | ||
C5—O1—N2—C3 | 0.0 (9) | O1—C5—C6—O7 | −7.7 (11) |
C8—O3—C3—N2 | −7.7 (13) | C14—C9—C10—C11 | −2.6 (15) |
C8—O3—C3—C4 | 174.8 (8) | I4—C9—C10—C11 | −177.5 (8) |
O1—N2—C3—O3 | −177.8 (8) | C9—C10—C11—C12 | 6.9 (16) |
O1—N2—C3—C4 | −0.1 (10) | C10—C11—C12—C13 | −7.7 (18) |
O3—C3—C4—C5 | 177.9 (8) | C10—C11—C12—O12 | 179.4 (9) |
N2—C3—C4—C5 | 0.1 (10) | C15—O12—C12—C11 | −173.9 (10) |
O3—C3—C4—I4 | 0.4 (12) | C15—O12—C12—C13 | 12.4 (14) |
N2—C3—C4—I4 | −177.4 (6) | C11—C12—C13—C14 | 3.9 (17) |
C3—C4—C5—O1 | −0.1 (10) | O12—C12—C13—C14 | 176.8 (8) |
I4—C4—C5—O1 | 177.3 (5) | C10—C9—C14—C13 | −1.1 (13) |
C3—C4—C5—C6 | 179.6 (9) | I4—C9—C14—C13 | 173.7 (6) |
I4—C4—C5—C6 | −3.0 (15) | C12—C13—C14—C9 | 0.7 (13) |
N2—O1—C5—C4 | 0.1 (10) | F16—C16—C17—O18 | 86.1 (11) |
N2—O1—C5—C6 | −179.7 (8) | F17—C16—C17—O18 | −151.2 (9) |
C7—O7—C6—O6 | −1.6 (14) | F18—C16—C17—O18 | −29.4 (12) |
C7—O7—C6—C5 | 177.5 (8) | F16—C16—C17—O17 | −96.1 (11) |
C4—C5—C6—O6 | −8.3 (16) | F17—C16—C17—O17 | 26.7 (12) |
O1—C5—C6—O6 | 171.4 (9) | F18—C16—C17—O17 | 148.5 (9) |
C4—C5—C6—O7 | 172.5 (9) |
D—H···A | D—H | H···A | D···A | D—H···A |
C8—H8C···O12i | 0.98 | 2.58 | 3.475 (14) | 152 |
C11—H11···F16ii | 0.95 | 2.56 | 3.405 (17) | 148 |
C15—H15C···O6iii | 0.98 | 2.62 | 3.503 (14) | 151 |
Symmetry codes: (i) x, y+1, z; (ii) x, y−1, z; (iii) x+1, y, z. |
Funding information
The authors acknowledge the Universiti Teknologi MARA for funding under the UMP-IIUM-UiTM Sustainable Research Collaboration Grant [600–RMC/SRC/5/3(043/2020)].
References
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