7,8,9,10-Tetra-hydro-2-methyl-cyclo-hepta-[b]indol-6(5H)-one.

The title compound, C(14)H(15)NO, was synthesized from 2-hydroxy-methyl-enecyclo-hepta-none via a Japp-Klingemann acid-catalyzed cyclization. The seven-membered ring exhibits a slightly distorted envelope conformation. N-H⋯O hydrogen bonds form a centrosymmetric dimer; C-H⋯O hydrogen bonds and π-π stacking inter-actions (the centers of the atoms involved in the stacking interaction are separated by 3.504 Å) give rise to another type of centrosymmetric dimer. In combination, these inter-actions create a stair-like chain of mol-ecules that inter-acts only loosely with neighboring chains via van der Waals inter-actions and weak C-H⋯π contacts.

2,2-Dimethyl-2,3-dihydro-pyrano[2,3-a]carbazol-4(11H)-one.

The title compound, C(17)H(15)NO(2), was prepared from 1-hydroxy-carbazole and 3,3-dimethyl-acrylic acid with a mixture of AlCl(3) and POCl(3) as the cyclization catalyst. Owing to the presence of the -CMe(2)- group, the mol-ecule is not quite planar. In the crystal structre, strong N-H⋯O hydrogen bonds and weaker C-H⋯π inter-actions occur, and a slipped π-π stacking inter-action [centroid-centroid separation = 3.8425 (8) Å] is also observed.

2,2,9-Trimethyl-2,3-dihydro-pyrano[2,3-a]carbazol-4-(11H)-one.

The title compound, C(18)H(17)NO(2), was prepared from 1-hydr-oxy-7-methyl-carbazole and 3,3-dimethyl-acrylic acid with trifluoro-acetic acid as the cyclization catalyst. The mol-ecules contain an essentially planar 6-methyl-indole unit. The second aromatic ring is significantly bent away from the plane of this unit, with maximum deviations of 0.171 (1) and 0.185 (1) Šfor two of the C atoms. In the crystal structure, there are neither N-H⋯O hydrogen bonds nor π-π stacking between the aromatic sections of neighboring mol-ecules. There is only one weak C-H⋯O hydrogen bond and a number of weak C-H⋯π inter-actions.

2,2,10-Trimethyl-2,3-dihydro-pyrano[2,3-a]carbazol-4(11H)-one.

The title compound, C(18)H(17)NO(2), was prepared from 1-hydr-oxy-8-methyl-carbazole and 3,3-dimethyl-acrylic acid with trifluoro-acetic acid as the cyclization catalyst. Due to the -CMe(2)- group, the mol-ecule is not quite planar. The packing is dominated by the strong N-H⋯O hydrogen bonds and some weaker C-H⋯O and C-H⋯π inter-actions. π-π Stacking inter-actions [centroid-centroid separation = 3.806 (2) Å] join neighboring mol-ecules into loosely connected inversion dimers.