research communications
R)-5-[(R)-3-(4-chlorophenyl)-5-methyl-4,5-dihydroisoxazol-5-yl]-2-methylcyclohex-2-enone
of (aLaboratoire de Synthése Organique et de Physico-Chimie Moléculaire, Département de Chimie, Faculté des Sciences, Semlalia BP 2390, Marrakech 40001, Morocco, bInstitut de Chimie Moléculaire de Reims, CNRS UMR 7312, Bat. Europol Agr, Moulin de la Housse, UFR Sciences, BP 1039, 51687 Reims Cédex 2, France, and cLaboratoire de Chimie de Coordination, 205 route de Narbonne, 31077 Toulouse Cedex 04, France
*Correspondence e-mail: itto35@hotmail.com_or_aititto@uca.ma
The title compound, C17H18ClNO2, was prepared and isolated as a pure diastereoisomer, using followed by a succession of fractional crystallizations. Its exact structure was fully identified via 1H NMR and confirmed by X-ray diffraction. It is built up from a central five-membered dihydroisoxazole ring to which a p-chlorophenyl group and a cyclohex-2-enone ring are attached in the 3 and 5 positions. The cyclohex-2-one and isoxazoline rings each exhibit an The crystal packing features C—H⋯O, C—H⋯N and C—H⋯π interactions, which generate a three-dimensional network.
Keywords: isoxazole derivatives; absolute configuration; natural products; pharmaceutical activities; crystal structure.
CCDC reference: 1983547
1. Chemical context
In recent years, isoxazole and isoxazoline derivatives have been considered to be good drug candidates because of their broad spectrum of pharmaceutical activities, such as antitumoral (Kamal et al., 2010), antibacterial (Calí et al., 2004), antiviral (Deng et al., 2009) and anti-inflammatory (Pedada et al., 2016). Cycloaddition and heterocyclization reactions have been widely used as synthetic methods for obtaining isoxazoles (Nieto et al., 2019). In terms of selectivity, 1,3-dipolar cycloaddition reactions of with dipolarophiles, such as C=C, C=S or C=N, give high stereoselectivity (Ait Itto et al., 2013), while which are less sterically hindered dipoles, lead to poor stereoselectivity (Feddouli et al., 2006). This was confirmed in our recent work (Oubella et al., 2019) in which the 1,3-cycloaddition reaction of diarylnitrilimines with (R)-carvone gave the corresponding pyrazoles isolated as the unique (3aR,5R,7aR) diastereoisomer, while the isoxazoles prepared with were isolated as (R,R)/(R,S) diastereoisomeric mixtures with a slight predominance of (R, R). In the present work, we report the separation, identification by 1H NMR spectroscopy, and X-ray structural analysis of the slightly major diastereoisomer of the isoxazole obtained by the 1,3-dipolar cycloaddition of 4-chlorobenzonitrile oxide with (R)-carvone.
2. Structural commentary
The title compound is built up from a central five-membered dihydroisoxazol ring to which a p-chlorophenyl group and a cyclohex-2-enone ring are attached to atoms C2 and C1 at the 3 and 5 positions, respectively (Fig. 1). Atom C1 also bears a methyl group. The of R/R at atoms C1 and C11 were confirmed by the (Parsons et al., 2013). This structure is closely related to the previously reported isoxazole derivative having a methyl group in place of atom Cl 3 (Oubella et al., 2019). The isoxazole ring has an on C1 as indicated by the puckering parameters of Q2 = 0.145 (3) Å and φ2 = 138.1 (11)°. The puckering parameters for the cyclohexene ring, Q = 0.449 (3) Å, θ = 126.0 (4)° and φ = 189.2 (5)°, agree with an on C11. The mean plane of the isoxazole ring makes a dihedral angle of 13.4 (2)° with the C21–C26 benzene ring, whereas it makes a dihedral angle of 66.2 (1)° with the mean plane of the C11–C16 ring.
3. Supramolecular features
The packing of the structure features weak C—H⋯N and C—H⋯O interactions (C4—H42⋯N1i and C12—H12B⋯O13ii; symmetry codes as in Table 1). The C—H⋯N interactions build up a linear chain along the a-axis direction, while the C—H⋯O interactions make a helical chain along the b-axis direction, forming a layer parallel to the ab plane (Fig. 2). Between the layers, a C—H⋯π interaction is observed (C23—H23⋯Cg1iii; Table 1), where Cg1 is the centroid of the C21–C26 benzene ring.
4. Database survey
A search in the Cambridge Structural Database (CSD, version 5.40, update August 2019; Groom et al., 2016) for organic compounds with structures containing a 2-isoxazoline ring revealed 284 hits. Introducing a methyl group on position 5 reduced this number to 15 and searching for structures containing a phenyl ring attached to position 3 gave only seven hits. A comparison of related distances and angles within the 2-isoxazoline ring shows a good agreement between all these structures, with a systematically short C2—N1 bond with lengths ranging from 1.274 to 1.285 Å, corresponding to a C=N double bond. A larger discrepancy is observed for the dihedral angle between the isoxazol mean plane and the benzene ring in the (S)-3-(2,6-dichlorophenyl)-5-[(2,5-diphenylpyrrolidin-1-yl)carbonyl]-5-methyl-4,5-dihydroisoxazole compound (Houk et al., 1984); at 66.8°, this is much larger than the value of 13.4 (2)° observed for the title compound. This larger dihedral angle is related to the occurrence of two Cl atoms in the 2 and 5 positions on the phenyl ring.
5. Synthesis and crystallization
As shown in Fig. 3, (R)-carvone, 1, was reacted with nitrile oxide, 2, generated in situ from the corresponding oxime according to our recently described methodology (Oubella et al., 2019). The corresponding isoxazole, 3, was obtained in 80% yield, as an (R,R)/(R,S) diastereoisomeric mixture. The 1H NMR spectrum of 3 clearly shows a splitting of both the methyl and methylene groups in the α position of the newly formed stereogenic center of the isoxazole nucleus (Fig. 4a). The former gave rise to two singlets at 1.44 ppm and 1.48 ppm, respectively, while the latter is seen as two pairs of doublets, one at 2.90 and 3.20 ppm (J = 16.9 Hz) and the other at 2.75 and 3.30 ppm (J = 16.7 Hz). Integrating the corresponding 1H NMR signals allowed us to quantify the ratio of the diastereoisomereric mixture as 58:42. After several attempts at separation, either by or a series of fractional crystallizations by slow evaporation from a chloroform solution of 3, we managed to separate the diastereoisomer 3a, the title compound, as pure single crystals suitable for crystallographic analysis. Its 1H NMR spectrum (Fig. 4b) is mainly characterized by the isoxazolic methyl group resonating as a singlet at 1.44 ppm, and the methylene group appeared as two doublets at 2.90 ppm (J = 16.9 Hz) and 3.20 ppm (J = 16.9 Hz).
6. Refinement
Crystal data, data collection and structure . All H atoms attached to C atoms were fixed geometrically and treated as riding with C—H = 0.99 Å (methylene), 0.98 Å (methyl) or 0.95 Å (methine), and with Uiso(H) = 1.2Ueq(C) for methylene and methine or Uiso(H) = 1.5Ueq(C) for methyl H atoms.
details are summarized in Table 2Supporting information
CCDC reference: 1983547
https://doi.org/10.1107/S2056989020001991/is5530sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989020001991/is5530Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989020001991/is5530Isup3.cml
Data collection: APEX2 (Bruker, 2015); cell
SAINT (Bruker, 2015); data reduction: SAINT (Bruker, 2015); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL2016 (Sheldrick, 2015b).C17H18ClNO2 | Dx = 1.355 Mg m−3 |
Mr = 303.77 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, P212121 | Cell parameters from 5113 reflections |
a = 6.4590 (2) Å | θ = 2.8–27.9° |
b = 7.3545 (3) Å | µ = 0.26 mm−1 |
c = 31.3436 (12) Å | T = 105 K |
V = 1488.91 (10) Å3 | Box, colourless |
Z = 4 | 0.31 × 0.26 × 0.18 mm |
F(000) = 640 |
Bruker APEXII CCD diffractometer | 3019 independent reflections |
Radiation source: micro-focus sealed tube | 2827 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.057 |
φ and ω scans | θmax = 26.4°, θmin = 1.3° |
Absorption correction: multi-scan (SADABS; Bruker, 2015) | h = −8→8 |
Tmin = 0.694, Tmax = 0.746 | k = −9→9 |
16529 measured reflections | l = −38→39 |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.035 | w = 1/[σ2(Fo2) + (0.060P)2 + 0.137P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.105 | (Δ/σ)max = 0.001 |
S = 1.19 | Δρmax = 0.40 e Å−3 |
3019 reflections | Δρmin = −0.23 e Å−3 |
193 parameters | Extinction correction: SHELXL2016 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.014 (4) |
Primary atom site location: dual | Absolute structure: Flack x determined using 1100 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013) |
Secondary atom site location: difference Fourier map | Absolute structure parameter: −0.09 (4) |
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 | ||
C1 | 0.6484 (4) | 0.6566 (4) | 0.64093 (9) | 0.0150 (6) | |
C2 | 0.4125 (4) | 0.4711 (4) | 0.60439 (8) | 0.0140 (6) | |
C3 | 0.6216 (4) | 0.4598 (4) | 0.62542 (9) | 0.0158 (6) | |
H31 | 0.728644 | 0.425833 | 0.605242 | 0.019* | |
H32 | 0.621273 | 0.374475 | 0.649026 | 0.019* | |
C4 | 0.7886 (4) | 0.7654 (4) | 0.61166 (9) | 0.0197 (6) | |
H41 | 0.739550 | 0.755866 | 0.582840 | 0.030* | |
H42 | 0.927089 | 0.718468 | 0.613353 | 0.030* | |
H43 | 0.787990 | 0.890632 | 0.620283 | 0.030* | |
C11 | 0.7057 (4) | 0.6782 (4) | 0.68816 (9) | 0.0134 (6) | |
H11 | 0.713927 | 0.808792 | 0.694138 | 0.016* | |
C12 | 0.5419 (4) | 0.5983 (4) | 0.71777 (9) | 0.0181 (6) | |
H12A | 0.411443 | 0.660009 | 0.712739 | 0.022* | |
H12B | 0.522661 | 0.470911 | 0.710757 | 0.022* | |
C13 | 0.5961 (4) | 0.6140 (4) | 0.76455 (9) | 0.0155 (6) | |
C14 | 0.8176 (4) | 0.6073 (4) | 0.77632 (9) | 0.0163 (6) | |
C15 | 0.9600 (4) | 0.5958 (4) | 0.74575 (9) | 0.0175 (6) | |
H15 | 1.097590 | 0.587139 | 0.754279 | 0.021* | |
C16 | 0.9173 (4) | 0.5956 (4) | 0.69867 (9) | 0.0182 (6) | |
H16A | 0.922229 | 0.471584 | 0.688155 | 0.022* | |
H16B | 1.024450 | 0.664296 | 0.684169 | 0.022* | |
C17 | 0.8694 (5) | 0.6108 (4) | 0.82302 (9) | 0.0222 (6) | |
H17A | 1.016154 | 0.596660 | 0.826631 | 0.033* | |
H17B | 0.798826 | 0.513186 | 0.837226 | 0.033* | |
H17C | 0.826500 | 0.724750 | 0.835047 | 0.033* | |
C21 | 0.3164 (4) | 0.3268 (4) | 0.57902 (8) | 0.0146 (6) | |
C22 | 0.1345 (4) | 0.3588 (4) | 0.55578 (9) | 0.0164 (6) | |
H22 | 0.077055 | 0.474733 | 0.555387 | 0.020* | |
C23 | 0.0396 (4) | 0.2195 (4) | 0.53343 (9) | 0.0180 (6) | |
H23 | −0.081403 | 0.240979 | 0.518175 | 0.022* | |
C24 | 0.1273 (5) | 0.0476 (4) | 0.53409 (9) | 0.0176 (6) | |
C25 | 0.3067 (5) | 0.0123 (4) | 0.55656 (9) | 0.0194 (6) | |
H25 | 0.364066 | −0.103682 | 0.556670 | 0.023* | |
C26 | 0.3997 (4) | 0.1524 (4) | 0.57889 (9) | 0.0181 (6) | |
H26 | 0.520399 | 0.129473 | 0.594145 | 0.022* | |
N1 | 0.3162 (3) | 0.6195 (3) | 0.61149 (7) | 0.0152 (5) | |
O1 | 0.4384 (3) | 0.7345 (3) | 0.63657 (6) | 0.0161 (4) | |
O13 | 0.4603 (3) | 0.6257 (3) | 0.79158 (6) | 0.0220 (5) | |
Cl1 | 0.00864 (11) | −0.12745 (10) | 0.50590 (2) | 0.0242 (2) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0094 (12) | 0.0177 (14) | 0.0179 (14) | 0.0039 (11) | −0.0007 (11) | −0.0012 (11) |
C2 | 0.0129 (13) | 0.0170 (14) | 0.0121 (13) | 0.0026 (11) | 0.0016 (10) | 0.0016 (11) |
C3 | 0.0132 (13) | 0.0177 (14) | 0.0166 (14) | 0.0055 (11) | −0.0009 (11) | −0.0029 (11) |
C4 | 0.0159 (13) | 0.0272 (16) | 0.0161 (14) | 0.0024 (13) | −0.0020 (12) | 0.0036 (12) |
C11 | 0.0098 (12) | 0.0144 (13) | 0.0162 (13) | 0.0015 (10) | −0.0007 (11) | −0.0021 (10) |
C12 | 0.0111 (13) | 0.0221 (15) | 0.0210 (14) | −0.0027 (11) | 0.0007 (11) | −0.0013 (11) |
C13 | 0.0154 (13) | 0.0098 (12) | 0.0211 (14) | −0.0021 (11) | 0.0037 (11) | −0.0003 (11) |
C14 | 0.0185 (13) | 0.0139 (13) | 0.0164 (14) | −0.0008 (12) | 0.0000 (11) | 0.0009 (11) |
C15 | 0.0119 (14) | 0.0218 (14) | 0.0188 (14) | 0.0015 (12) | −0.0007 (11) | 0.0027 (11) |
C16 | 0.0113 (13) | 0.0260 (16) | 0.0172 (15) | 0.0045 (12) | 0.0018 (11) | −0.0002 (12) |
C17 | 0.0230 (14) | 0.0263 (16) | 0.0171 (14) | −0.0038 (14) | 0.0013 (12) | 0.0018 (13) |
C21 | 0.0156 (13) | 0.0159 (14) | 0.0123 (13) | 0.0008 (11) | 0.0037 (11) | 0.0008 (10) |
C22 | 0.0166 (12) | 0.0152 (13) | 0.0173 (13) | 0.0021 (12) | 0.0006 (11) | 0.0004 (11) |
C23 | 0.0167 (13) | 0.0214 (14) | 0.0161 (13) | 0.0013 (12) | −0.0007 (11) | 0.0004 (11) |
C24 | 0.0215 (15) | 0.0181 (14) | 0.0131 (13) | −0.0032 (12) | 0.0004 (12) | −0.0017 (11) |
C25 | 0.0260 (15) | 0.0151 (13) | 0.0172 (14) | 0.0031 (12) | −0.0007 (13) | 0.0001 (11) |
C26 | 0.0197 (14) | 0.0191 (14) | 0.0155 (14) | 0.0038 (12) | −0.0032 (12) | 0.0004 (11) |
N1 | 0.0134 (10) | 0.0162 (11) | 0.0160 (11) | −0.0017 (11) | −0.0019 (9) | −0.0017 (10) |
O1 | 0.0106 (9) | 0.0156 (9) | 0.0222 (10) | 0.0035 (7) | −0.0048 (8) | −0.0048 (8) |
O13 | 0.0191 (10) | 0.0249 (10) | 0.0220 (10) | −0.0008 (10) | 0.0067 (8) | −0.0005 (9) |
Cl1 | 0.0307 (4) | 0.0197 (4) | 0.0223 (4) | −0.0051 (3) | −0.0041 (3) | −0.0033 (3) |
C1—O1 | 1.478 (3) | C14—C17 | 1.502 (4) |
C1—C4 | 1.517 (4) | C15—C16 | 1.501 (4) |
C1—C11 | 1.534 (4) | C15—H15 | 0.9300 |
C1—C3 | 1.537 (4) | C16—H16A | 0.9700 |
C2—N1 | 1.276 (4) | C16—H16B | 0.9700 |
C2—C21 | 1.464 (4) | C17—H17A | 0.9600 |
C2—C3 | 1.505 (4) | C17—H17B | 0.9600 |
C3—H31 | 0.9700 | C17—H17C | 0.9600 |
C3—H32 | 0.9700 | C21—C26 | 1.391 (4) |
C4—H41 | 0.9600 | C21—C22 | 1.402 (4) |
C4—H42 | 0.9600 | C22—C23 | 1.384 (4) |
C4—H43 | 0.9600 | C22—H22 | 0.9300 |
C11—C12 | 1.525 (4) | C23—C24 | 1.386 (4) |
C11—C16 | 1.532 (3) | C23—H23 | 0.9300 |
C11—H11 | 0.9800 | C24—C25 | 1.380 (4) |
C12—C13 | 1.512 (4) | C24—Cl1 | 1.740 (3) |
C12—H12A | 0.9700 | C25—C26 | 1.383 (4) |
C12—H12B | 0.9700 | C25—H25 | 0.9300 |
C13—O13 | 1.223 (3) | C26—H26 | 0.9300 |
C13—C14 | 1.478 (4) | N1—O1 | 1.398 (3) |
C14—C15 | 1.331 (4) | ||
O1—C1—C4 | 106.7 (2) | C15—C14—C17 | 123.3 (3) |
O1—C1—C11 | 105.7 (2) | C13—C14—C17 | 117.3 (2) |
C4—C1—C11 | 112.6 (2) | C14—C15—C16 | 125.5 (3) |
O1—C1—C3 | 103.4 (2) | C14—C15—H15 | 117.3 |
C4—C1—C3 | 111.9 (2) | C16—C15—H15 | 117.2 |
C11—C1—C3 | 115.5 (2) | C15—C16—C11 | 112.0 (2) |
N1—C2—C21 | 120.6 (2) | C15—C16—H16A | 109.2 |
N1—C2—C3 | 114.1 (2) | C11—C16—H16A | 109.2 |
C21—C2—C3 | 125.3 (2) | C15—C16—H16B | 109.2 |
C2—C3—C1 | 100.8 (2) | C11—C16—H16B | 109.2 |
C2—C3—H31 | 111.6 | H16A—C16—H16B | 107.9 |
C1—C3—H31 | 111.6 | C14—C17—H17A | 109.5 |
C2—C3—H32 | 111.6 | C14—C17—H17B | 109.5 |
C1—C3—H32 | 111.6 | H17A—C17—H17B | 109.5 |
H31—C3—H32 | 109.4 | C14—C17—H17C | 109.5 |
C1—C4—H41 | 109.5 | H17A—C17—H17C | 109.5 |
C1—C4—H42 | 109.5 | H17B—C17—H17C | 109.5 |
H41—C4—H42 | 109.5 | C26—C21—C22 | 118.5 (3) |
C1—C4—H43 | 109.5 | C26—C21—C2 | 120.4 (2) |
H41—C4—H43 | 109.5 | C22—C21—C2 | 121.0 (2) |
H42—C4—H43 | 109.5 | C23—C22—C21 | 120.6 (3) |
C12—C11—C16 | 109.6 (2) | C23—C22—H22 | 119.7 |
C12—C11—C1 | 112.3 (2) | C21—C22—H22 | 119.7 |
C16—C11—C1 | 112.4 (2) | C22—C23—C24 | 119.1 (3) |
C12—C11—H11 | 107.4 | C22—C23—H23 | 120.4 |
C16—C11—H11 | 107.4 | C24—C23—H23 | 120.4 |
C1—C11—H11 | 107.4 | C25—C24—C23 | 121.5 (3) |
C13—C12—C11 | 113.6 (2) | C25—C24—Cl1 | 119.3 (2) |
C13—C12—H12A | 108.9 | C23—C24—Cl1 | 119.2 (2) |
C11—C12—H12A | 108.9 | C24—C25—C26 | 118.9 (3) |
C13—C12—H12B | 108.9 | C24—C25—H25 | 120.6 |
C11—C12—H12B | 108.9 | C26—C25—H25 | 120.6 |
H12A—C12—H12B | 107.7 | C25—C26—C21 | 121.4 (3) |
O13—C13—C14 | 121.6 (3) | C25—C26—H26 | 119.3 |
O13—C13—C12 | 120.7 (2) | C21—C26—H26 | 119.3 |
C14—C13—C12 | 117.6 (2) | C2—N1—O1 | 109.9 (2) |
C15—C14—C13 | 119.4 (2) | N1—O1—C1 | 109.61 (19) |
Cg1 is the centroid of the C21–C26 ring. |
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H42···N1i | 0.96 | 2.62 | 3.572 (4) | 173 |
C12—H12B···O13ii | 0.97 | 2.54 | 3.488 (4) | 165 |
C23—H23···Cg1iii | 0.93 | 2.71 | 3.554 (3) | 151 |
Symmetry codes: (i) x+1, y, z; (ii) −x+1, y−1/2, −z+3/2; (iii) x−1/2, −y+1/2, −z+1. |
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