1-(1-Hydr-oxy-9H-carbazol-2-yl)-3-methyl-but-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 mol-ecules, A and B, which are virtually superimposable but not related by any translational or other pseudosymmetry. Both independent mol-ecules are almost planar [r.m.s. deviations from planarity = 0.053†(1) and 0.079†(1)†à in A and B, respectively] and contain an intramolecular O-H⋯O hydrogen bond. Each type of mol-ecules 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 mol-ecules allows the formation of alternating C-H⋯π inter-actions between A and B mol-ecules of parallel stacks.