11-Butyl-3-methoxy-11H-benzo[a]carbazole

The title compound, C21H21NO, consists of a carbazole skeleton with a methoxybenzene ring fused to the carbazole, and a butyl group attached to the carbazole N atom. The carbazole skeleton is nearly planar [maximum deviation = 0.078 (2) Å], and it is oriented at a dihedral angle of 4.22 (4)° with respect to the adjacent methoxybenzene ring.

The title compound, C 21 H 21 NO, consists of a carbazole skeleton with a methoxybenzene ring fused to the carbazole, and a butyl group attached to the carbazole N atom. The carbazole skeleton is nearly planar [maximum deviation = 0.078 (2) Å ], and it is oriented at a dihedral angle of 4.22 (4) with respect to the adjacent methoxybenzene ring.
Benzo -annulated carbazole ring systems are found only rarely in natural products. The benzo[a]carbazoles, containing an aromatic ring fused to the a-face of the carbazole nucleus, are potential candidates for cancer treatment as a result of DNA intercelative binding properties (Carini et al., 2001). A series of simple benzo[a]carbazoles have been shown to bind to estrogen receptors and inhibit the growth of mammary tumors of rats (Angerer & Prekajac, 1986). Some benzo[a]carbazoles exhibit a pronounced antitumor activity against leukemia, renal tumor, colon cancer, and malignant melanoma tumor cell lines (Pindur & Lemster, 1997). Benzo[a]carbazole derivatives have also found extensive application as photographic materials (Oliveira et al., 2005).
The title compound consists of a carbazole skeleton with a methoxy benzoato group fused to the a-face of the carbazole nucleus, and a butyl group attached to atom N9 (Fig. 1), where the bond lengths (Allen et al., 1987) and angles are within normal ranges, and generally agree with those in compounds (II)-(X). In all structures atom N9 is substituted.
In the crystal structure, molecules are alongated along the c axis and stacked along the b axis (Fig. 2).

Experimental
For the preparation of the title compound, (I), a solution of 3-methoxy-11H -benzo[a]carbazole (1.00 g, 4.0 mmol) in dichloromethane (20 ml) was cooled to 273 K, and then sodium hydroxide (2 ml, 50%), tetrabutylammonium hydrogen sulfate (0.10 g) and butyl bromide (0.62 g, 4.5 mmol) were added. The mixture was stirred for 1 h at 273 K, and then 2 h at 298 K. It was washed with hydrochloric acid (50 ml, 10%) and the organic layer was dried with anhydrous magnesium sulfate.
The solvent was evaporated under reduced pressure and the residue was crystallized from methanol (yield; 1.15 g, 93%, m.p. 369 K).