(Z)-Ethyl 2-hy­droxy-4-oxo-4-(1,4,5,6,8-penta­meth­oxy­naphthalen-2-yl)but-2-enoate

Pillay, A.; Khorasani, S.; de Koning, C.B.

doi:10.1107/S1600536812049203

Volume 69
Part 1
Pages o54-o55
January 2013

Received 28 November 2012
Accepted 30 November 2012
Online 8 December 2012

Key indicators
Single-crystal X-ray study
T = 173 K
Mean (C-C) = 0.004 Å
Disorder in main residue
R = 0.053
wR = 0.118
Data-to-parameter ratio = 13.6
Details

(Z)-Ethyl 2-hydroxy-4-oxo-4-(1,4,5,6,8-pentamethoxynaphthalen-2-yl)but-2-enoate

Adushan Pillay,^a Sanaz Khorasani ^a and Charles B. de Koning ^a ^*

^aMolecular Sciences Institute, School of Chemistry, University of the Witwatersrand, PO Wits 2050, Johannesburg, South Africa
Correspondence e-mail: charles.dekoning@wits.ac.za

The title compound, C₂₁H₂₄O₉, crystallizes with two independent molecules in the asymmetric unit which are almost centrosymmetrically related to each other. The ethanoate group in one of the two molecules is disordered over two positions with a site-occupation factor of 0.880 (7) for the major occupied site. In the crystal, the 1,3-diketone group exists in the keto-enol isomeric form due to the stabilizing effect of the intramolecular O-HO hydrogen bond present in this form. The compound packs as a layered structure in which C-H [pi] and C-HO interactions are present within and between the layers.

Related literature

For the synthesis of the title compound, see: de Koning et al. (1991). This forms part of our research programme directed towards the synthesis of the natural phytotoxic naphthoquinone, marticin, see: Pillay et al. (2012).

Experimental

Crystal data

C₂₁H₂₄O₉
M_r = 420.40
Triclinic, $[P \overline 1]$
a = 6.8019 (4) Å
b = 12.3042 (6) Å
c = 24.3971 (12) Å
= 100.002 (4)°
= 93.080 (4)°
= 98.748 (4)°
V = 1980.67 (18) Å³
Z = 4
Mo K radiation
= 0.11 mm^-1
T = 173 K
0.39 × 0.16 × 0.07 mm

Data collection

Bruker APEXII CCD diffractometer
19594 measured reflections
7793 independent reflections
3172 reflections with I > 2(I)
R_int = 0.083

Refinement

R[F² > 2(F²)] = 0.053
wR(F²) = 0.118
S = 0.84
7793 reflections
572 parameters
54 restraints
H-atom parameters constrained
_max = 0.21 e Å^-3
_min = -0.25 e Å^-3

Table 1
Hydrogen-bond geometry (Å, °)

Cg1, Cg2 and Cg3 are the centroids of the C1A/C2A/C7A-C10A, C2A-C7A and C2B-C7B rings, respectively.

D-HA	D-H	HA	DA	D-HA
O7A-H7AO6A	0.84	1.77	2.499 (3)	144
O7B-H7BO6B	0.84	1.77	2.497 (3)	143
C17B-H17DO6Bⁱ	0.98	2.43	3.234 (4)	139
C19A-H19BO9Bⁱⁱ	0.98	2.45	3.419 (4)	168
C19B-H19EO9Aⁱⁱⁱ	0.98	2.47	3.440 (5)	172
C20A-H20BO4B^iv	0.98	2.50	3.384 (4)	150
C20B-H20EO4A^v	0.98	2.57	3.382 (4)	140
C20B-H20FO9Bⁱ	0.98	2.58	3.460 (4)	150
C18A-H18ACg3^vi	0.98	2.66	3.486 (3)	142
C18A-H18CCg1^vi	0.98	2.92	3.844 (3)	158
C18B-H18FCg2^vii	0.98	2.66	3.522 (3)	147
C21A-H21ACg2^vii	0.98	2.96	3.845 (3)	150
Symmetry codes: (i) -x+1, -y+2, -z+1; (ii) -x+2, -y+1, -z+1; (iii) -x, -y+2, -z; (iv) x, y-1, z; (v) x, y+1, z; (vi) x+1, y, z; (vii) x-1, y, z.

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-NT (Bruker, 2005); data reduction: SAINT-NT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009) and SCHAKAL99 (Keller, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT6876 ).

Acknowledgements

This work was supported by SABINA (Southern African Biochemistry and Informatics for Natural Products Network), the National Research Foundation [NRF, GUN 2053652 and IRDP of the NRF (South Africa) for financial support provided by the Research Niche Areas programme], Pretoria, and the University of the Witwatersrand (Science Faculty Research Council).

References

Bruker (2005). APEX2 and SAINT-NT (includes XPREP and SADABS). Bruker AXS Inc., Madison, Wisconsin, USA.
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.
Keller, E. (1999). SCHAKAL99. University of Freiberg, Germany.
Koning, C. B. de, Giles, R. G. F. & Green, I. R. (1991). J. Chem. Soc. Perkin Trans. 1, pp. 2743-2748.
Pillay, A., Rousseau, A. L., Fernandes, M. A. & de Koning, C. B. (2012). Tetrahedron, 68, 7116-7121.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.
Spek, A. L. (2009). Acta Cryst. D65, 148-155.

organic compounds