Dimethyl (E)-2-(N-phenylacetamido)but-2-enedioate

The title compound, C14H15NO5, was obtained from the reaction of acetanilide with dimethyl acetylenedicarboxylate in the presence of potassium carbonate. The C=C double bond adopts an E configuration and the geometry around the amide N atom is almost planar rather than pyramidal (mean deviation of 0.0032 Å from the C3N plane). The packing of the molecules in the crystal structure is stabilized by intermolecular C—H⋯O hydrogen bonds.

The title compound, C 14 H 15 NO 5 , was obtained from the reaction of acetanilide with dimethyl acetylenedicarboxylate in the presence of potassium carbonate. The C C double bond adopts an E configuration and the geometry around the amide N atom is almost planar rather than pyramidal (mean deviation of 0.0032 Å from the C 3 N plane). The packing of the molecules in the crystal structure is stabilized by intermolecular C-HÁ Á ÁO hydrogen bonds.   Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x À 1 2 ; Ày þ 1 2 ; z À 1 2 ; (ii) x þ 1 2 ; Ày þ 1 2 ; z À 1 2 ; (iii) Àx þ 1; Ày; Àz.

Comment
Hydroamidation of alkynes has proved to be an effective approach to construct enamides (Severin & Doye, 2007;Goossen et al. 2005;Cacchi & Fabrizi 2005), which are important substructures often found in natural products and synthetic drugs (Yet et al. 2003). In our studies on the reaction of dimethyl acetylenedicarboxylate with acetanilide in the presence of potassium carbonate, the title compound was formed via base mediated hydroamidation.
An X-ray diffraction study has been carried out to determine the structure (Fig. 1). The C=C double bond adopts an E configuration. The geometry around the amide N atom is planar rather than pyramidal, as reflected by the small mean deviation of 0.0032 Å from the least-squares plane defined by the four constituent atoms N1, C2, C7 and C11, which is probably due to the large degree of conjugation between the amide N atom and the adjacent acetyl group (the maximium deviation from the least-squares plane defined by N1, C2, C7, C11 and O5 is 0.0956 (9) Å for N1) (Penney, et al. 1995).

Experimental
To a solution of acetanilide (0.27 g, 2.00 mmol) and dimethyl acetylenedicarboxylate (0.29 g, 2.04 mmol) in toluene (10 ml), potassium carbonate (0.57 g, 4.13 mmol) was added at room temperature. The mixture was then refluxed for 12 h under an atmosphere of dinitrogen. After concentration, the residue was purified by flash chromatography (ethyl acetate/petroleum = 1:2) to give the product as a white solid. Yield: 0.37 g, 67.2%. 1  One of the reflections, (-5 3 5), was found to be inconsistent with an I(obs) value more that 10 times SigmaW diffeent from I(calc). Inspection of the frame showed that the reflection was located at the frame edge and it was thus omitted from the refinement.
All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were positioned geometrically (C-H = 0.93, 0.93 or 0.96Å for phenyl, methylene or methyl H atoms respectively) and included in the refinement in the riding model approximation. The displacement parameters of vinyl and phenyl H atoms were set to 1.2U eq (C), while those of methyl H atoms were set to 1.5U eq (C). In the final Fourier map the highest peak is 0.72 Å from atom H8A and the deepest hole is 0.59 Å from atom C8. Fig. 1. The molecular structure of the title compound with the atom-labelling scheme, showing 30% probability displacement ellipoids.

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.