4-Methyl-7,8,9,10-tetrahydrocyclohepta[b]indol-6(5H)-one

In the title compound, C14H15NO, the seven-membered ring exhibits a slightly distorted twist-boat conformation. The pyrrole ring forms a dihedral angle of 1.44 (10)° with the fused benzene ring. N—H⋯O hydrogen bonds form a centrosymmetric dimer and weak C—H⋯π interactions are also found in the crystal structure.

In the title compound, C 14 H 15 NO, the seven-membered ring exhibits a slightly distorted twist-boat conformation. The pyrrole ring forms a dihedral angle of 1.44 (10) with the fused benzene ring. N-HÁ Á ÁO hydrogen bonds form a centrosymmetric dimer and weak C-HÁ Á Á interactions are also found in the crystal structure.

Related literature
For a related crystal structure, see: Sridharan et al. (2008).

Comment
The title compound has been analysed as part of our crystallographic studies on cyclohept [b]indoles and their substituted analogues. Sridharan et al.(2008) have reported the X-ray crystal sructure of the related compound, 7,8,9,10-tetrahydro-2methylcyclohepta[b]indol-6(5H)-one. In that paper, the seven-membered ring is stated to exhibit a slightly distorted envelope conformation.
In the title compound, C 14 H 15 NO ( Fig. 1), the seven-membered ring exhibits a slightly distorted twist-boat conformation.
The pyrrole ring forms a dihedral angle of 1.44 (10)° with the fused benzene ring.

Experimental
A solution of 2-(2-(1-methylphenyl)hydrazono)cycloheptanone (0.230 g, 0.001 mol) in a mixture of acetic acid (20 ml) and conc. hydrochloric acid (5 ml) was refluxed on an oil bath pre-heated to 398-403 K for 4 h. The reaction was monitored by TLC. After the completion of the reaction, the contents were cooled and poured into ice water with stirring. The separated brown solid was filtered and purified by passing through a column of silica gel and eluting with a petroleum ether-ethyl acetate (95:5 v/v) mixture to yield the title compound (0.140 g, 66%). This product was recrystallized using ethanol.

Refinement
H5 attached to N5 was located in a difference Fourier map and refined isotropically; the final N-H distance was 0.94 (3) Å. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93, 0.96 and 0.97 Å for Csp 2 , methyl and methylene H atoms, respectively. U iso (H) = xU eq (C), where x = 1.5 for methyl H atoms and 1.2 for other C-bound H atoms.   -7,8,9,10-tetrahydrocyclohepta[b]indol-6(5H)-one