Ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate

In the title compound, C9H13NO2S, the mean planes of thiophene ring [maximum deviation = 0.0042 (10) Å] and ethoxycarbonyl group [0.0242 (15) Å] are almost coplanar [dihedral angle between them = 0.68 (11)°]. The H atoms of the two methyl groups attached to the thiophene ring are each disordered over two orientations with site-occupancy ratios of 0.77 (4):0.23 (4) and 0.84 (4):0.16 (4). An intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked by N—H⋯O hydrogen bonds into an infinite wave-like chain running parallel to the b-axis direction. The crystal structure also features C—H⋯π interactions.

In the title compound, C 9 H 13 NO 2 S, the mean planes of thiophene ring [maximum deviation = 0.0042 (10) Å ] and ethoxycarbonyl group [0.0242 (15) Å ] are almost coplanar [dihedral angle between them = 0.68 (11) ]. The H atoms of the two methyl groups attached to the thiophene ring are each disordered over two orientations with site-occupancy ratios of 0.77 (4):0.23 (4) and 0.84 (4):0.16 (4). An intramolecular N-HÁ Á ÁO hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds into an infinite wave-like chain running parallel to the b-axis direction. The crystal structure also features C-HÁ Á Á interactions.

Experimental
Ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate was prepared according to the reported method (Gewald, 1965). The obtained solid was recrystallized from ethanol to give the title compound. Brown plates were obtained by slow evaporation from ethanol solution at room temperature.

Refinement
The atoms H1N1 and H2N1 were located in a difference fourier map and refined freely [N-H = 0.88 (3)

Figure 1
The molecular structure of the title compound with 30% probability displacement ellipsoids. The dashed line represents the intramolecular N-H···O hydrogen bond.

Figure 2
The crystal packing of the title compound. The dashed lines represent the hydrogen bonds. For clarity sake, hydrogen atoms not involved in hydrogen bonding have been omitted.  (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0041 (9) 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.