(E)-3-Dimethylamino-1-(2,5-dimethylthiophen-3-yl)prop-2-en-1-one

In the title compound, C11H15NOS, the 3-(dimethylamino)prop-2-en-1-one unit is approximately planar [maximum deviation = 0.0975 (14) Å] and its mean plane of seven non-H atoms makes a dihedral angle of 6.96 (10)° with the thiophene ring. In the crystal, molecules are linked by pairs of C—H⋯O hydrogen bonds into inversion dimers with R 2 2(14) ring motifs. The dimers are stacked along the c axis through C—H⋯π interactions. The two methyl groups, attached to the thiophene ring and the amino N atom, are each disordered over two orientations, with site-occupancy ratios of 0.59 (4):0.41 (4) and 0.74 (4):0.26 (4), respectively.

In the title compound, C 11 H 15 NOS, the 3-(dimethylamino)prop-2-en-1-one unit is approximately planar [maximum deviation = 0.0975 (14) Å ] and its mean plane of seven non-H atoms makes a dihedral angle of 6.96 (10) with the thiophene ring. In the crystal, molecules are linked by pairs of C-HÁ Á ÁO hydrogen bonds into inversion dimers with R 2 2 (14) ring motifs. The dimers are stacked along the c axis through C-HÁ Á Á interactions. The two methyl groups, attached to the thiophene ring and the amino N atom, are each disordered over two orientations, with site-occupancy ratios of 0.59 (4):0.41 (4) and 0.74 (4):0.26 (4), respectively.

Experimental
Cg1 is the centroid of the S1/C1-C4 ring.  As part of a program designed to investigate the biological activity of tricyclic and tetracyclic heterocyclic systems containing a thiophene ring as the central nucleus (Ghorab et al., 2006), recently we have put forward a convenient way to synthesize thiophene derivatives as anticancer agents (Al-Said et al., 2011;Shaaban et al., 2010). A survey of the literature showed that thiophene derivatives possess antihypertensive action (Krantz et al., 1990), platelet aggregation inhibition (Kikugawa & Ichino, 1973) and antineoplastic activities (Gogte et al., 1967;Medower et al., 2008). In addition, several nitrogen, oxygen and sulfur-containing heterocyclic compounds incorporating thiophene residues were found to possess interesting biological properties Hassan et al., 1998). In continuation of our work on the synthesis of a novel thiophene derivative which might show significant anticancer activity, the title compound was prepared and its crystal structure is now reported.

D-HÁ
The molecular structure of the title compound is shown in Fig. 1. The mean plane of dimethylthiophene ring [S1/C1-C6; maximum deviation = 0.0180 (12) Å at atom C6] forms a dihedral angle of 6.63 (12) In the crystal (Fig. 2), molecules are linked by pairs of intermolecular C10-H10A···O1 hydrogen bonds into inversion dimers with an R 2 2 (14) ring motif (Bernstein et al., 1995) and are further stacked parallel to the a axis. The crystal packing is further stabilized by C-H···π interaction (Table 1), involving Cg1 which is the centroid of S1/C1-C4 ring.

Experimental
A mixture of 1-(2,5-dimethylthiophen-3-yl)ethanone (1.54 g, 0.01 mole) and dimethylformamide-dimethylacetal (1.19 g, 0.01 mole) in dry N,N-dimethylformamide (20 ml) was heated under reflux for 5 h. The reaction mixture was cooled and poured into ice water. The solid obtained was then recrystallized from ethanol to give the title compound. Single crystals suitable for X-ray structural analysis were obtained by slow evaporation from an N,N-dimethylformamide solution at room temperature.

Refinement
The U iso (H) = 1.2 or 1.5U eq (C). Rotating group model was also applied to the other methyl groups in the final refinement.

Figure 1
The molecular structure of the title compound with atom labels and 30% probability displacement ellipsoids.

Figure 2
A crystal packing diagram of the title compound viewed along the b axis. The dashed lines represent the hydrogen bonds.
For clarity sake, H atoms not involved in hydrogen bonding have been omitted.

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.