Ethyl 3-amino-4H-thieno[2,3-b]pyridine-2-carboxylate

The molecule of the title compound, C10H10N2O2S, is essentially planar, except for the ethyl group, which is twisted away from the carboxyl plane by −90.5 (3)°. In the crystal structure, molecules are linked into a zigzag sheet propagating along the b axis by intermolecular N—H⋯O and N—H⋯N hydrogen bonds.

The molecule of the title compound, C 10 H 10 N 2 O 2 S, is essentially planar, except for the ethyl group, which is twisted away from the carboxyl plane by À90.5 (3) . In the crystal structure, molecules are linked into a zigzag sheet propagating along the b axis by intermolecular N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: CI2735).   Thieno[2,pyridine derivatives are of great importance owing to their wide biological properties (Litvinov et al.,2005).
The title compound is one of the key intermediates in our synthetic investigations of antitumor drugs. We report here its crystal structure.
The thieno[2,3-b]pyridine ring system of the title molecule ( Fig.1) is essentially planar. The amino group and the carbonyl group are nearly coplanar with the heterocyclic ring system. The ethyl group is twisted perpendicular to the remaining part In the crystal structure, the molecules are linked into a zigzag sheet propagating along the b axis by intermolecular N-H···O and N-H···N hydrogen bonds (Fig. 2).

Experimental
A mixture of 2-chloro-3-cyanopyridine (3.3 g, 0.023 mol), ethyl 2-mercaptoacetate (3.62 g, 0.03 mol), sodium carbonate (2.65 g, 0.025 mol) and anhydrous ethanol (12.0 ml) was heated for 4.5 h under reflux. The reaction mixture was cooled to ambient temperature and added to water (150 ml). The resultant precipitate was stirred for 45 min and then filtered. The filter cake was washed with two portions of water (25 ml) and dried to yield the title compound as a yellow solid (5.032 g, 95.1% yield). Single crystals suitable for X-ray analysis were obtained by slow evaporation of a tetrahydrofuran solution.

Refinement
H atoms of the amino group were located in a difference map and refined freely. The reminaing H atoms were positioned geometrically (C-H = 0.93-0.97 Å) and refined using a riding model, with U iso (H) = 1.2-1.5U eq (C). Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level.