Crystal structure of methyl 3-(3-fluorophenyl)-1-methyl-1,3a,4,9b-tetrahydro-3H-thiochromeno[4,3-c]isoxazole-3a-carboxylate

In the title compound, C19H18FNO3S, the five-membered oxazolidine ring adopts an envelope conformation with the methine C atom of the fused bond as the flap. Its mean plane is oriented at a dihedral angle of 50.38 (1)° with respect to the fluorophenyl ring. The six-membered thiopyran ring has a half-chair conformation and its mean plane is almost coplanar with the fused benzene ring, making a dihedral angle of 4.94 (10)°. The two aromatic rings are inclined to one another by 85.96 (11)°, and the mean planes of the oxazolidine and thiopyran rings are inclined to one another by 57.64 (12)°. In the crystal, molecules are linked by C—H⋯π interactions, forming a three-dimensional structure.


Related literature
For background on thio-containing heterocyclic rings and for related structures, see for example: Khan et al. (2008a,b H atoms treated by a mixture of independent and constrained refinement Á max = 0.52 e Å À3 Á min = À0.24 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).
In the crystal, molecules are linked by C-H···π interactions forming a three-dimensional structure ( Table 1).

S2. Synthesis and crystallization
To a solution of methyl (Z)-2-(((2-formylphenyl)thio)methyl)-3-phenylacrylate (1 mmol) and N-methyl hydroxylamine hydrochloride (1.1 mmol) in acetonitrile (10 ml) was added pyridine (0.2 mmol). The solution was refluxed until the completion of the reaction (monitored by TLC). The solvent was then removed under vacuum. The crude product was subjected to column chromatography on silica gel (100-200 mesh) using petroleum ether-ethyl acetate (9:1) as eluent, which successfully provided the pure product as a colorless solid. The product was dissolved in chloroform and heated for 2 min. The resulting solution was subjected to crystallization by slow evaporation of the solvent for 48 h resulting in the formation of single crystals of the title compound.

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The H atoms attached to atom C1 were freely refined. All other H atoms were fixed geometrically and allowed to ride on their parent atoms: C-H = 0.93-0.98 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the title compound, with the atom labelling. Displacement ellipsoids are drawn at the 30% probability level. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.52 e Å −3 Δρ min = −0.24 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0079 (14) Special details 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. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.38912 (