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

In the title molecule, C13H12ClNO, the dihedral angle between the benzene and pyrrole rings is 1.38 (9)°. The cycloheptene ring adopts a distorted twist chair and sofa conformation. Intermolecular N—H⋯O hydrogen bonds form an R 2 2(10) loop in the crystal packing. Further, weak C—H⋯O and C—H⋯π (involving the benzene ring) interactions are found in the crystal structure.

In the title molecule, C 13 H 12 ClNO, the dihedral angle between the benzene and pyrrole rings is 1.38 (9) . The cycloheptene ring adopts a distorted twist chair and sofa conformation. Intermolecular N-HÁ Á ÁO hydrogen bonds form an R 2 2 (10) loop in the crystal packing. Further, weak C-HÁ Á ÁO and C-HÁ Á Á (involving the benzene ring) interactions are found in the crystal structure.
RJB acknowledges the NSF MRI program (grant No. CHE-0619278) for funds to purchase an X-ray diffractometer.

Experimental
A solution of 2-(2-(4-chlorophenyl)hydrazono)cycloheptanone (0.486 g, 0.001 mol) in a mixture of acetic acid (20 ml) and hydrochloric acid (5 ml) was refluxed on an oil bath pre-heated to 398 K for 2 h. The contents were then cooled and poured onto cold water with stirring. The brown solid which was separated by passing through a column of silica gel and eluted with (98:2, v/v) petroleum ether-ethyl acetate mixture yielded the title compound (0.167 g, 72%). This was recrystallized from ethanol.

Refinement
The N-H atom was located in a difference Fourier map and refined freely. Other H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.95-0.99 Å and U iso (H) = 1.2U eq (parent atom).

Computing details
Data collection: CrysAlis PRO (Agilent, 2011); cell refinement: CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009  The molecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level. H atoms are shown as small spheres of arbitrary radius.  Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.