2-Amino-N-(2-methoxyphenyl)-4,5-dimethylthiophene-3-carboxamide

In the title compound, C14H16N2O2S, the two aromatic rings make a dihedral angle of 13.9 (1)°. The crystal structure is stabilized by both inter- and intramolecular N—H⋯O, C—H⋯O and C—H⋯N hydrogen bonds.

In the title compound, C 14 H 16 N 2 O 2 S, the two aromatic rings make a dihedral angle of 13.9 (1) . The crystal structure is stabilized by both inter-and intramolecular N-HÁ Á ÁO, C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds.

Comment
Thiophene derivates containing amino and carboxyl functions have been found to exhibit anti-viral, antiinflamatory and antimicrobial activities (Mohan & Saravanan, 2003). Specifically the 2-amino-carboxylic acid esters were recognized as allosteric enhancers for A1 adenosine receptors (Bruns et al., 1990).
Interaction of 3-(2-thienyl alanine) with human phenyl alanine has been studied with a view to understand the mechanism of catalysis and substrate activation. Diffraction studies on bis 5-bromo-2-substituted thiophene derivatives have revealed the existence of S-S stacking interactions. Our earlier investigations on the structures of the biologically active thiophene carboxamide, has shown that the chloro substitution in the aryl amide group had a significant effect. The ortho-chloro group reversed the orientation of the amide linkage and favoured the formation of more intra molecular hydrogen bonds. The para-chloro substitution induces stabilizing effects via inter molecular hydrogen bonds. The compound in the present study bears a close structural relationship with the reported allosteric enhancers for adenosine and hence the structure has been investigated.
The molecular structure and the packing diagram are shown in Fig. 1 and 2, respectively. The molecular structure is stabilized by intra molecular C-H···O, N-H···O hydrogen bonds and intermolecular N-H···O interactions. (Table 2) The intra molecular C8 -H8···O1 and N1 -H1···O1 hydrogen bonds form pseudo-six membered rings and N2 -H2···O2 forms a pseudo five membered ring thus locking the molecular conformation and eliminating conformational flexibility.

Experimental
The title compound was synthesized by mixing of ethyl methyl ketone (0.72 g, 0.01 mol) and o-methoxycyanoacetanilide (1.94 g, 0.01 mol) and refluxing the mixture for 1 h (Gewald et al., 1966) in the presence of 4.0 ml of diethylamine. Sulfur powder (1.28 g, 0.04 mol) and 40 ml ethanol were then added and the resulting solution was heated for 2 h at 323 K. Crystals were grown by slow evaporation in a solution of isopropyl alcohol (yield 50%).  Fig. 1. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms.Dashed lines indicate intramolecular hydrogen bonds; H atoms not involved in hydrogen bonding have been omitted.