Methyl 6-eth­oxy-3-phenyl-3a,4-dihydro-3H-chromeno[4,3-c]isoxazole-3a-car­boxylate

G Suresh; J Srinivasan; M Bakthadoss; S Aravindhan

doi:10.1107/S1600536812051720

. 2013 Jan 4;69(Pt 2):o180. doi: 10.1107/S1600536812051720

Methyl 6-ethoxy-3-phenyl-3a,4-dihydro-3H-chromeno[4,3-c]isoxazole-3a-carboxylate

G Suresh ^a, J Srinivasan ^b, M Bakthadoss ^b, S Aravindhan ^a,^*

PMCID: PMC3569242 PMID: 23424465

Abstract

In the title compound, C₂₀H₁₉NO₅, the dihedral angle between the mean plane of the pyran ring (which has a half-chair conformation) and the benzene ring of the chromeno ring system is 7.21 (7)°. The dihedral angle between the mean plane of the chromeno ring system and the isoxazole ring is 21.78 (6)°, while the isoxazole ring forms a dihedral angle of 72.60 (8)° with the attached phenyl ring. In the crystal, molecules are linked via pairs of C—H⋯O hydrogen bonds, forming inversion dimers with an R ² ₂(10) ring motif. These dimers are linked via C—H⋯N hydrogen bonds, forming chains along [001].

Related literature

For the biological activity of chromenopyrroles, see: Caine (1993 ▶), and of benzopyran and isoxazolidine derivatives, see: Lin et al. (1996 ▶); Hu et al. (2004 ▶). For uses of isoxazole derivatives, see: Baraldi et al. (1987 ▶); Eddington et al. (2002 ▶). For related structures, see: Gangadharan et al. (2011 ▶); Swaminathan et al. (2011 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶).

Experimental

Crystal data

C₂₀H₁₉NO₅
M _r = 353.36
Monoclinic,
a = 12.9342 (6) Å
b = 7.5591 (2) Å
c = 18.7138 (8) Å
β = 105.440 (2)°
V = 1763.63 (12) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 298 K
0.25 × 0.20 × 0.10 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.976, T _max = 0.990
13064 measured reflections
4245 independent reflections
3253 reflections with I > 2σ(I)
R _int = 0.017

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.125
S = 1.03
4245 reflections
237 parameters
H-atom parameters constrained
Δρ_max = 0.35 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 2012 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ▶).

Supplementary Material

Click here for additional data file.^{(21KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812051720/su2543sup1.cif

e-69-0o180-sup1.cif^{(21KB, cif)}

Click here for additional data file.^{(203.8KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812051720/su2543Isup2.hkl

e-69-0o180-Isup2.hkl^{(203.8KB, hkl)}

Click here for additional data file.^{(6.9KB, cml)}

Supplementary material file. DOI: 10.1107/S1600536812051720/su2543Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C6—H6A⋯O4ⁱ	0.97	2.55	3.3875 (19)	145
C8—H8⋯N1ⁱⁱ	0.98	2.52	3.4269 (19)	154

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

GS and SA thank the UGC, India, for financial support and GS thanks the SAIF, IIT-Madras, for the instrumentation facility.

supplementary crystallographic information

Comment

Chromenopyrrole compounds are used in the treatment of impulsive disorders (Caine, 1993). It is well known that benzo-pyran and isoxazolidine derivatives possess interesting biological and pharmacological activities (Lin et al., 1996; Hu et al., 2004). Isoxazole and its derivatives are key intermediates for the preparation of products which mimic natural compounds (Baraldi et al., 1987). They have been shown to possess anticonvulsant activity (Eddington et al., 2002). Herein we report on the synthesis and the crystal structure of the new title chromeno compound.

The molecular structure of the title molecule is illustrated in Fig. 1. In the chromeno ring system the pyran ring has a half chair conformation. Its mean plane makes a dihedral angle with the benzene ring of 7.21 (7)°. The dihedral angle between the mean plane of the chromeno ring system (fusion of benzene and pyran rings) and the isoxazole ring (O2/N1/C7-C9) is 21.78 (6)°. The isoxazole ring also forms a dihedral angle of 72.60 (8)° with the phenyl ring (C15—C20). The geometric parameters of the title molecule agree well with those reported for closely related structures (Gangadharan et al., 2011; Swaminathan et al., 2011).

In the crystal, molecules are linked via pairs of C-H···O hydrogen bonds to form inversion dimers with an R²₂(10) ring motif (Bernstein et al., 1995; Table 1 and Fig. 2). These dimers are linked via C-H···N hydrogen bonds to form chains along the c axis.

Experimental

At 283 - 293 K, NCS (4 mmol) was added pinch wise over 3 h to a solution of ((E)-methyl2-((2ethoxy-6-((E)-(hydroxyimino)methyl)phenoxy)methyl) -3-phenylacrylate (2 mmol) in CCl₄. After Et₃N (4 mmol) was added to the reaction mixture which was stirred at room temperature for 2 h. After completion of the reaction, the mixture was evaporated under reduced pressure and the resulting crude mass was diluted with water (15 ml) and extracted with ethyl acetate (3 × 15 ml). The combined organic layers were washed with brine (2 × 10 ml) and dried over anhydrous Na₂SO₄. The organic layer was evaporated and purified by column chromatography (silica gel 60–120 mesh 7% EtOAc in hexanes) to provide the desired pure title product as a colourless solid. Crystals suitable for X-ray diffraction analysis were obtained by slow evaporation of a solution in ethyl acetate.