Ethyl 2-[2-(4-hy-droxy-3-meth-oxy-benzyl-idene)hydrazin-1-yl-idene]-3,4-dimethyl-2,3-dihydro-1,3-thia-zole-5-carboxyl-ate.

The title compound, C(16)H(19)N(3)O(4)S, is almost planar, with a dihedral angle of 2.88†(9)° between the mean planes of the benzene and thia-zole rings. The mol-ecule adopts an E conformation about the two C=N bonds, with a C-N-N-C torsion angle of -177.01†(11)°. An intra-molecular C-H⋯O hydrogen bond exists between a thia-zole methyl group and the formic acid ethyl ester carbonyl O atom. In the crystal, mol-ecules are linked by O--H⋯O hydrogen bonds, forming chains propagating along [2-10]. The chains are linked via C-H⋯O hydrogen bonds with R(2) (2)(12) ring motifs, forming sheets lying parallel to (12-2). The sheets are further linked through out-of-plane C-H⋯N hydrogen bonds with R(2) (2)(12) ring motifs and C-H⋯π inter-actions, forming an inter-esting three-dimensional supra-molecular architecture.