8,8-Diethyl-1,4,5,8-tetra­hydro­naphthalene-1,4,5-trione

Andrés Vega; Oney Ramirez-Rodríguez; Maximiliano Martínez-Cifuentes; Andrés Ibañez; Ramiro Araya-Maturana

doi:10.1107/S1600536809001755

. 2009 Jan 17;65(Pt 2):o345. doi: 10.1107/S1600536809001755

8,8-Diethyl-1,4,5,8-tetrahydronaphthalene-1,4,5-trione

Andrés Vega ^a, Oney Ramirez-Rodríguez ^b, Maximiliano Martínez-Cifuentes ^b, Andrés Ibañez ^c, Ramiro Araya-Maturana ^b,^*

PMCID: PMC2968259 PMID: 21581946

Abstract

The title molecule, C₁₄H₁₄O₃, contains two fused six-membered carbon rings with keto groups at positions 1, 4 and 5 and a gem-diethyl group at position 8. The molecule is close to planar (maximum deviation = 0.044 Å), with one ethyl group at each side of the molecular plane, with exception of the keto group at position 1 which is slightly deviated from the plane and disordered over two positions one on each side of it (occupancies 0.80/0.20). The packing of the molecule shows weak bonded chains along a through C—H⋯O contacts and two intramolecular C—H⋯O interactions are also present.

Related literature

For the biologically active dimethyl analog, see: Araya-Maturana et al. (2002 ▶); for its use as a substrate for Diels-Alder cycloadditions with 2,4-hexadienol, see: Araya-Maturana et al. (1999 ▶) and for the synthesis of biologically active compounds, see: Araya-Maturana et al. (2006 ▶); Mendoza et al. (2005 ▶); Rodríguez et al. (2007 ▶). For details of the synthesis of the 4,4-dimethyl analog, see: Castro et al. (1983 ▶); Vega et al. (2008 ▶).

Experimental

Crystal data

C₁₄H₁₄O₃
M _r = 230.25
Orthorhombic,
a = 12.7454 (8) Å
b = 10.8015 (7) Å
c = 8.8598 (5) Å
V = 1219.72 (13) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 150 (2) K
0.49 × 0.48 × 0.46 mm

Data collection

Siemens SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 1999 ▶) T _min = 0.958, T _max = 0.961
6581 measured reflections
2159 independent reflections
2119 reflections with I > 2σ(I)
R _int = 0.012

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.099
S = 1.00
2159 reflections
166 parameters
15 restraints
H-atom parameters constrained
Δρ_max = 0.26 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Data collection: SMART-NT (Bruker, 2001 ▶); cell refinement: SAINT-NT (Bruker, 1999 ▶); data reduction: SAINT-NT; program(s) used to solve structure: SHELXTL-NT (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL-NT; molecular graphics: SHELXTL-NT; software used to prepare material for publication: SHELXTL-NT.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809001755/gw2058sup1.cif

e-65-0o345-sup1.cif^{(18.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809001755/gw2058Isup2.hkl

e-65-0o345-Isup2.hkl^{(106.2KB, hkl)}

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

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯O1ⁱ	0.95	2.27	3.207 (2)	169
C9—H9A⋯O2	0.99	2.40	3.014 (2)	120
C11—H11B⋯O2	0.99	2.39	3.027 (2)	122

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors gratefully acknowledge generous financial support from FONDECYT 1071077.

supplementary crystallographic information

Comment

The title quinone (I) is closely related to its biologically active dimethyl analog 8,8-dimethylnaphtalene-1,4,5(8H)-trione (Araya-Maturana et al. 2002), which has been used as substrate for highly regioselective Diels-Alder cycloadditions with 2,4-hexadienol (Araya-Maturana et al. 1999) and for the synthesis of biologically active compounds (Rodríguez et al. 2007; Araya-Maturana et al. 2006; Mendoza et al. 2005). The ¹H-NMR spectrum of the title compound exhibits equivalence of both ethyl groups, evidencing the existence of a symmetry plane in the molecule. It displays a single triplet for both methyl groups but two sextuplets for the methylene protons of the ethyl substituents; with couplings constant of 7.3 Hz and 15.4 Hz for the vecinal and geminal ones respectively. This evidences a rotational restriction for the chains. The non-equivalence of the signals of methylene protons in a non-chiral molecule could be envisoned supposing a rotational constrain exerted by the non bonding electrons of the near carbonyl group, avoiding the rotation of the bond between methylene groups and the quaternary carbon bearing the geminal ethyl groups. This hypotesis based on NMR solution data was tested for the present crystal structure.

The molecule I contains two six membered carbon rings fused, a p-quinone and a dienone core (Scheme 1). The dienone ring is highly planar mainly because of the insaturations in the carbon skeleton, while the quinonic framework displays a slightly distorted boat conformation, with one keto oxygen atom slightly out of the plane of the rest of the ring (see torsion angles). As described in the experimental section, the keto oxygen atom O3 is disordered over two positions of ocuppancy 0.80 and 0.20. placed at opposite sides of the molecular plane. This could be related to the equivalence of the methylene ¹H-NMR signals in solution in the following way: the two conformations are probably very close (if not equal) in energy and rapid interconversion occurs in the NMR timescale. The situation is consistent with the observation of two positions for the keto oxygen atom in the crystal strcuture.

The crystal packing of the molecule shows weak bonded zigzag chains along the a cell axis, through C—H···O interactions, as depicted in Figure 2.

Experimental

Synthesis of I. The title compound was prepared by oxydation of the corresponding hydroquinone B; obtained by rearrangement of the furane parent compound A (Vega et al., 2008); with MnO₂ as shown in Fig. 3. This procedure have been previously described for the 4,4-dimethyl analog (Castro et al., 1983). X-ray quality crystals were obtained through recrystallization from benzene.

Spectroscopic Details. ¹H and ¹³C NMR spectra were acquired using a Bruker AVANCE DRX 300 spectrometer operating at 300.13 MHz (¹H) or 75.47 MHz (¹³C). All measurements were carried out at a probe temperature of 300 K. ¹HNMR (CDCl₃): 0.62(6H, t, J = 7.5 Hz, 2X CH₃); 1.70(2H, dq, J₁ = 7.5 Hz, J₂ = 13.8 Hz, 2X CHH,); 2.52(2H, dq, J₁ = 7.5 Hz, J₂ = 13.8 Hz, 2X CHH); 6.53(1H, d, J = 10.2 Hz); 6.58(1H, d, J = 10.2 HZ). ¹³CNMR(CDCl₃): 8.42, 31.41, 48.13, 130.77, 132.79, 135.32, 135.57, 152.59, 154.51, 182.46, 183.13, 186.76.