1-(1-Hydr­oxy-9H-carbazol-2-yl)-3-methyl­but-2-en-1-one

The title compound, C(17)H(15)NO(2), was prepared as one of two products of the AlCl(3)/POCl(3)-catalysed reaction of 9-carbazol-1-ol with 3,3-dimethyacrylic acid. It crystallizes with two crystallographically independent mol­ecules, A and B, which are virtually superimposable but not related by any translational or other pseudosymmetry. Both independent mol­ecules are almost planar [r.m.s. deviations from planarity = 0.053 (1) and 0.079 (1) Å in A and B, respectively] and contain an intramolecular O—H⋯O hydrogen bond. Each type of mol­ecules is connected via pairs of N—H⋯O hydrogen bonds, forming centrosymmetric A (2) and B (2) dimers which are, in turn, arranged in offset π-stacks extending along the a-axis direction. The offset of the dimers and the tilt angle of the mol­ecules allows the formation of alternating C—H⋯π inter­actions between A and B mol­ecules of parallel stacks.