Ethyl 4-chloro-2-[(2-nitrophenyl)hydrazono]-3-oxobutyrate

The title compound, C₁₂H₁₂N₃O₅, adopts a keto-hydrazo tautomeric form stabilized by intra­molecular hydrogen bonds. The aromatic ring and aliphatic chain, which adopt a trans configuration about the C=N double bond, are nearly coplanar, with a dihedral angle of 7.56 (1)° between them. The mol­ecules pack via weak inter­molecular C—H...O hydrogen bonds which, together with intra­molecular N—H...O bonds, form an S(6)S(6)[R₂²(13)]S(6)S(6) motif.

Ethyl 4-chloro-2-[(4-nitro­phen­yl)hydrazono]-3-oxobutyrate

The title compound, C₁₂H₁₂N₃O₅, adopts a keto-hydrazo tautomeric form stabilized by an intra­molecular hydrogen bond. The aromatic ring and aliphatic chain, which adopt a trans configuration about the N—N bond, are nearly coplanar, with a dihedral angle of 18.30 (6)° between them. The mol­ecules pack via weak inter­molecular C—H...O hydrogen bonds which, together with an intra­molecular N—H...O bond, form an S(6)C(13) motif. The structure is further stabilized by C—H...π and π–π inter­actions.

Eth­yl 4-chloro-3-oxo-2-(phenyl­hydrazono)butyrate

The title compound, C₁₂H₁₃ClN₂O₃, adopts a keto–hydrazo tautomeric form stabilized by an intra­molecular N—H...O hydrogen bond. The configuration around the C=N bond is trans. The dihedral angle between the aromatic ring and the aliphatic chain is 5.52 (9)°. Symmetry-related mol­ecules are linked via C—H...O hydrogen bonds to form chains along the b axis.

(E)-Ethyl 4-chloro-3-[2-(2-fluoro­phenyl)hydrazono]butanoate

The title compound, C₁₂H₁₂ClFN₂O₃, adopts a keto–hydrazo tautomeric form stabilized by an intra­molecular N—H...O hydrogen bond. The whole mol­ecule is roughly planar, the largest deviation from the mean plane being 0.328 (3) Å for the terminal methyl C atom of the ethyl side chain.

(Z)-Ethyl 4-chloro-2-[2-(2-methoxy­phen­yl)hydrazono]-3-oxobutanoate

The title compound, C₁₃H₁₅ClN₂O₄, adopts a keto–hydrazo tautomeric form stabilized by intra­molecular N—H...O hydrogen bonds. The phenyl­hydrazone fragment is planar within ±0.028 (2) Å. The dihedral angle between the phenyl­hydrazone and oxobutanoate planes is 8.15 (9)°. Symmetry-related mol­ecules are linked via C—H...O hydrogen bonds to form chains along [101].

(Z)-Ethyl 4-chloro-2-[2-(2-chloro­phen­yl)hydrazono]-3-oxobutanoate

The title compound, C₁₂H₁₂Cl₂N₂O₃, adopts a keto-hydrazo tautomeric form stabilized by an intra­molecular hydrogen bond. The mol­ecule can be considered as consisting of two connected fragments, viz. a chloro­phenyl­hydrazone group, with a Z configuration, and an oxobutanoate group. The mol­ecule is roughly planar, the dihedral angle between the benzene ring and the plane including the aliphatic chain being 4.7 (2)°.