Ethyl (Z)-4′-(4-eth­oxy-1-hy­droxy-3,4-dioxobut-1-en-1-yl)-[1,1′-biphen­yl]-3-carboxyl­ate

The 1,3-diketone group of the title compound, C₂₁H₂₀O₆, exists in a keto–enol form stabilized by a strong intra­molecular O—H...O hydrogen bond. As a result, a planar (mean deviation = 0.0099 Å) six-membered hydrogen-bonded ring is formed. The C—O and C—C bond lengths suggest significant electron delocalization in the ring. The dihedral angle between the six-membered hydrogen-bonded ring and its adjacent benzene ring is 8.78 (5)° and that between the benzene rings is 19.70 (5)°. In the crystal, mol­ecules are packed in a layered structure parallel to the b axis through C—H...O and π–π inter­actions [centroid–centroid distance between stacked benzene rings = 3.868 (2) Å].