2-Morpholino-4-oxo-4,5-dihydrothiophene-3-carbonitrile

The title compound, C9H10N2O2S, was obtained from the treatment of ethyl 4-cyano-3-hydroxy-5-morpholinothiophene-2-carboxylate with concentrated HCl. The mean plane of the essentially planar dihydrothiophene ring is almost orthogonal to the mirror plane of the N-morpholine substituent, making a dihedral angle of 87.2 (2)°.

The title compound, C 9 H 10 N 2 O 2 S, was obtained from the treatment of ethyl 4-cyano-3-hydroxy-5-morpholinothiophene-2-carboxylate with concentrated HCl. The mean plane of the essentially planar dihydrothiophene ring is almost orthogonal to the mirror plane of the N-morpholine substituent, making a dihedral angle of 87.2 (2) .

Experimental
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: DN2498). The title compound was obtained via the treatment of ethyl 4-cyano-3-hydroxy-5-morpholinothiophene-2-carboxylate with concentrated HCl, and its structural formula was confirmed by the present study (Fig. 1).
Dihydrothiophene ring C5/C6/C7/C8/S1 is planar within 0.02 Å. Its least squares plane is almost orthogonal to the mirror plane of the N-morpholine substituent passing through C5, N1 and O1 atoms: the corresponding dihedral angle being 92.8 (2)°. Similar conformation is observed in the related structure with morpholine substituent attached to dihydrothiophene ring (Moghaddam et al., 2005).

S2. Experimental
Into a suspension of ethyl 4-cyano-3-hydroxy-5-morpholinothiophene-2-carboxylate (100 mg, 0.35 mmol) in MeOH (1.2 ml), was added concentrated HCl (0.2 ml) with stirring. The reaction mixture was heated in an oil bath at 60°C for 48 h to form a clear solution. The reaction solution was cooled to room temperature and the solvent was removed under reduced pressure. The resulting residue was neutralized with 2 N NaOH to pH 4. The precipitate was collected by filtration and rinsed with a solution of water/MeOH. The sample was dried under high vacuum to afford the desired compound as a white solid (52.1 mg, 58% yield). LC-MS (APCI, M+1) 211.2; 1 H NMR (300 MHz, DMSO-d 6 ) δ p.p.m. 3.87 (s, 3 H), 3.84 (dd, J=5.84, 2.07 Hz, 2 H), 3.68 -3.79 (m, 5 H). The product was recrystallized from EtOAc/hexane/dichloromethane to yield single crystals suitable for X-ray diffraction studies.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > 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.