Methyl 5-hydroxy-3-phenyl-1,2-oxazolidine-5-carboxylate

In the title compound, C11H13NO4, the isoxazolidine ring has an envelope conformation with the O atom as the flap. In the crystal, molecules are liked via N—H⋯O and bifurcated O—H⋯(O,N) hydrogen bonds forming chains propagating along [010]. There are also C—H⋯O interactions present.

In the title compound, C 11 H 13 NO 4 , the isoxazolidine ring has an envelope conformation with the O atom as the flap. In the crystal, molecules are liked via N-HÁ Á ÁO and bifurcated O-HÁ Á Á(O,N) hydrogen bonds forming chains propagating along [010]. There are also C-HÁ Á ÁO interactions present.
Nitrogen containing nucleophiles such as hydroxylamines and hydrazoic acid are widely employed in conjugation additions to α,β-unsaturated ketones (Wu et al., 2006). The title compound is a Michael addition product from the transformation of hydroxylamine to an α,β-unsaturated ketone ester. We report herein on the crystal structure of the title compound.
The molecular structure of the title molecule is shown in Fig. 1. The bond lengths (Allen et al., 1987) and angles are normal. The isoxazolidine ring possesses an envelope conformation with atom O1 as the flap.
In the crystal, molecules are linked via N-H···O and bifurcated O-H···O,N hydrogen bonds to form chains along the b axis (Table 1). These chains are linked via C-H···O interactions (Table 1).

Experimental
To the solution of (E)-methyl 2-oxo-4-phenylbut-3-enoate (0.019 g, 0.1 mmol) and hydroxylamine hydrochloride (0.07 g, 0.1 mmol) in dichloromethane (1 mL) was added triethylamine (0.012 g, 0.12mmol) at room temperature. The reaction mixture was stirred for 24 h at 273 K. The solvent was then removed under reduced pressure, and the residue was purified through column chromatography (petroleum ether: ethyl acetate = 3:1(V/V)). Single crystals, suitable for X-ray diffraction, were obtained by slow evaporation of an ethyl acetate solution at room temperature for 2 d.

Refinement
The NH H atom was located in a difference Fourier map and freely refined. The OH and C-bound H-atoms were included in calculated positions and treated as riding atoms: O-H = 0.82 Å, C-H = 0.93, 0.96, 0.97 and 0.98 Å for CH(aromatic), CH 3 , CH 2 and CH(methine) H-atoms, respectively, with U iso (H) = k × U eq (O,C), where k = 1.5 for OH and CH 3 H-atoms and = 1.2 for other H-atoms.

Computing details
Data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).  The molecular structure of the title molecule, with the atom numbering. 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 = 0.20 e Å −3 Δρ min = −0.12 e Å −3 Special details Experimental. Absorption correction: (CrysAlisPro; Oxford Diffraction, 2009) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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 > σ(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.