Ethyl 4-oxo-2,3,4,9-tetra­hydro-1H-carbazole-3-carboxyl­ate

Cevher Gündoğdu; Mustafa Göçmentürk; Yavuz Ergün; Barış Tercan; Tuncer Hökelek

doi:10.1107/S1600536811018678

. 2011 May 20;67(Pt 6):o1470–o1471. doi: 10.1107/S1600536811018678

Ethyl 4-oxo-2,3,4,9-tetrahydro-1H-carbazole-3-carboxylate

Cevher Gündoğdu ^a, Mustafa Göçmentürk ^a, Yavuz Ergün ^a, Barış Tercan ^b, Tuncer Hökelek ^c,^*

PMCID: PMC3120486 PMID: 21754841

Abstract

In the title compound, C₁₅H₁₅NO₃, the carbazole skeleton includes an ethoxycarbonyl group at the 3-position. In the indole ring system, the benzene and pyrrole rings are nearly coplanar, forming a dihedral angle of 0.89 (4)°. The cyclohexenone ring has an envelope conformation. In the crystal, intermolecular N—H⋯O and C—H⋯O hydrogen bonds link the molecules into a three dimensional network. A weak C—H⋯π interaction is also observed.

Related literature

For background to tetrahydrocarbazole systems present in indole-type alkaloids, see: Saxton (1983 ▶). For related structures, see: Hökelek et al. (1994 ▶, 1998 ▶, 1999 ▶, 2009 ▶); Patır et al. (1997 ▶); Hökelek & Patır (1999 ▶); Çaylak et al. (2007 ▶); Uludağ et al. (2009 ▶). For the use of 4-oxo-tetrahydrocarbazole in the syntheses of biologically active species, see: Kumar et al. (2008 ▶); Ergün et al. (2002 ▶); Li & Vince (2006 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₁₅H₁₅NO₃
M _r = 257.28
Orthorhombic,
a = 9.1057 (3) Å
b = 12.7031 (4) Å
c = 21.3874 (5) Å
V = 2473.89 (13) Å³
Z = 8
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 100 K
0.43 × 0.26 × 0.20 mm

Data collection

Bruker Kappa APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.960, T _max = 0.981
12029 measured reflections
2993 independent reflections
2258 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.102
S = 1.04
2993 reflections
177 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶) and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811018678/hb5881sup1.cif

e-67-o1470-sup1.cif^{(18.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811018678/hb5881Isup2.hkl

e-67-o1470-Isup2.hkl^{(144KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811018678/hb5881Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg3 is the centroid of the C5A/C5–C8,C8A ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N9—H9⋯O2ⁱ	0.885 (16)	2.044 (16)	2.9103 (15)	166.0 (15)
C3—H3⋯O1ⁱⁱ	1.00	2.41	3.4053 (17)	173
C11—H11A⋯Cg3ⁱⁱⁱ	0.99	2.86	3.7358 (15)	148

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

The authors are indebted to Anadolu University and the Medicinal Plants and Medicine Research Centre of Anadolu University, Eskişehir, Turkey, for the use of X-ray diffractometer.

supplementary crystallographic information

Comment

Tetrahydrocarbazole systems are present in the framework of a number of indole-type alkaloids of biological interest (Saxton, 1983). The structures of tricyclic, tetracyclic and pentacyclic ring systems with dithiolane and other substituents of the tetrahydrocarbazole core, have been reported previously (Hökelek et al., 1994; Patır et al., 1997; Hökelek et al., 1998; Hökelek et al., 1999; Hökelek & Patır, 1999). Although 4-oxo-tetrahydrocarbazoles rarely occur in nature, they have been increasingly important intermediates in the syntheses of indole or carbazole alkaloids and various biologically active heterocyclic compounds because of their unique structures. For instance, 4-oxo-tetrahydrocarbazole was used in the syntheses of antiemetic drugs, central nervous system active drugs and NPY-1 antagonists (Kumar et al., 2008). They have also been used in the syntheses of indole alkaloids (Ergün et al., 2002). Tetrahydrocarbazolone based antitumor active compounds and inhibitors of HIV integrase were synthesized from 4-oxo-tetrahydrocarbazoles (Li & Vince, 2006). The present study was undertaken to ascertain the crystal structure of the title compound, (I).

The molecule of the title compound contains a carbazole skeleton with an ethoxycarbonyl group at the 3 position, (Fig. 1), where the bond lengths are close to standard values (Allen et al., 1987) and generally agree with those in the previously reported compounds. In all structures atom N9 is substituted.

An examination of the deviations from the least-squares planes through individual rings shows that rings B (C4a/C5a/C8a/N9/C9a) and C (C5a/C5—C8/C8a) are nearly coplanar [with a maximum deviation of -0.012 (1) Å for atom C5a] with dihedral angle of B/C = 0.89 (4)°. Ring A (C1—C4/C4a/C9a) adopts envelope conformation with atom C2 displaced by -0.632 (2) Å from the plane of the other rings atoms, as in 3a,4,10,10b-tetrahydro-2H-furo[2,3-a]carbazol-5(3H)-one (Çaylak et al., 2007), 3,3-ethylenedithio-3,3a,4,5,10,10b-hexahydro-2H-furo[2,3-a]carbazole (Uludağ et al., 2009) and ethyl 1-oxo-1,2,3,4-tetrahydro-9H-carbazole-3-carboxylate (Hökelek et al., 2009).

In the crystal, intermolecular N—H···O and C—H···O hydrogen bonds link the molecules into a three dimensional network (Table 1 and Fig. 2). There also exists a weak C—H···π interaction (Table 1).

Experimental

A solution of 2,3-dichloro -5,6-dicyano-p-benzoquinone (9.36 g, 41.20 mmol) in tetrahydrofuran (20 ml, 90%) was added dropwise to a solution of ethyl 2,3,4,9-tetrahydro-1H -carbazole-3-carboxylate (5.00 g, 20.60 mmol) in tetrahydrofuran (50 ml, 90%) at 268 K. The reaction mixture was stirred for 10 min at 268 K, and then the solution was poured into sodium hydroxide (500 ml, 10%) and extracted with ethyl acetate. The organic layer was dried with anhydrous magnesium sulfate, and the solvent was removed. The residue was purified by chromatography using silica gel and ethyl acetate. After the solvent was evaporated, the product was crystallized from ether to yield colourless blocks of (I) (yield; 0.58 g, 11%, m.p. 396 K).