Ethyl (2S,4R)-4-(4-bromo­phen­yl)-2-hydr­oxy-5,10-dioxo-3,4,5,10-tetra­hydro-2H-benzo[g]chromene-2-carboxyl­ate

Wei Zhang; Yifeng Wang; Guangcun Zhang; Xiangsheng Xu

doi:10.1107/S1600536810001315

. 2010 Jan 16;66(Pt 2):o388. doi: 10.1107/S1600536810001315

Ethyl (2S,4R)-4-(4-bromophenyl)-2-hydroxy-5,10-dioxo-3,4,5,10-tetrahydro-2H-benzo[g]chromene-2-carboxylate

Wei Zhang ^a, Yifeng Wang ^a,^*, Guangcun Zhang ^a, Xiangsheng Xu ^a

PMCID: PMC2979899 PMID: 21579809

Abstract

In the crystal structure of the title compound, C₂₂H₁₇BrO₆, the quinone ring makes a dihedral angle of 81.84 (3)° with the benzene ring. The chiral C atoms, viz. the ring C atoms bearing the hydroxy and bromophenyl substituents, exhibit R and S configurations, respectively. The terminal ethyl group of the –CO₂CH₂CH₃ group is disordered over two sets of sites with site-occupancy factors of 0.64 (1) and 0.36 (1). Intermolecular O—H⋯O interactions further stabilize the crystal packing.

Related literature

For general background to the modification of hydroxyquinone, see: Rueping et al. (2008 ▶); Zhou et al. (2008 ▶). For related structures, see: Peng (2006 ▶); Nasiri et al. (2008 ▶).

Experimental

Crystal data

C₂₂H₁₇BrO₆
M _r = 457.27
Monoclinic,
a = 8.2993 (6) Å
b = 9.9445 (7) Å
c = 12.4884 (10) Å
β = 96.323 (2)°
V = 1024.43 (13) Å³
Z = 2
Mo Kα radiation
μ = 2.04 mm⁻¹
T = 296 K
0.32 × 0.30 × 0.28 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T _min = 0.520, T _max = 0.565
9887 measured reflections
4549 independent reflections
2257 reflections with I > 2σ(I)
R _int = 0.036

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.122
S = 1.00
4549 reflections
273 parameters
3 restraints
H-atom parameters constrained
Δρ_max = 0.30 e Å⁻³
Δρ_min = −0.37 e Å⁻³
Absolute structure: Flack (1983 ▶), 2082 Friedel pairs
Flack parameter: −0.008 (11)

Data collection: PROCESS-AUTO (Rigaku, 2006 ▶); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku, 2007 ▶); 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 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810001315/zq2026sup1.cif

e-66-0o388-sup1.cif^{(23.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810001315/zq2026Isup2.hkl

e-66-0o388-Isup2.hkl^{(218.3KB, 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
O4—H4⋯O1ⁱ	0.82	1.90	2.716 (4)	177

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Symmetry code: (i) Inline graphic .

Acknowledgments

We thank Professor Jian-Ming Gu, Zhejiang University, for his help.

supplementary crystallographic information

Comment

The Michael addition to α, β-unsaturated systems is an important carbon-carbon bond-forming reaction in organic synthesis. Hydroxyquinones, quinones bearing a hydroxy group on the quinone ring, are an important class of the naturally occurring quinones with diverse biological activity. The title compound, ethyl (2S,4R)-4-(4-bromophenyl)-2-hydroxy-5,10-dioxo-3,4,5,10-tetrahydro-2H-benzo[g]chromene-2-carboxylate, was synthesized from a Michael Addition of 2-hydroxy-1,4-naphthoquinone to β,γ-unsaturated α-keto esters. The crystal structure of the title compound (Fig. 1) contains a tricyclic ring system with two chiral centers, which is consisting of a quinone ring and a tetrahydropyrane. One carbon atom of the tetrahydropyrane structure is not coplanar with the backbone, lying 0.554 (4) Å from the mean plane of the rest backbone. The terminal ethyl group of CO₂CH₂CH₃ is disordered over two sites with site occupancy factors of 0.64 (1) and 0.36 (1). Moreover, weak O-H···O and C-H···O intermolecular interactions further stabilize the crystal structure.

Experimental

To a solution of (E)-ethyl 4-(4-bromophenyl)-2-oxobut-3-enoate (1 mmol) and 2-hydroxy-1,4-naphthoquinone (1 mmol) in 1,4-dioxane (3 ml) was added 3-((1S)-(6-methoxyquinolin-4-yl) (8-vinylquinuclidin-2-yl)methylamino)-4- ((S)-1-phenylethylamino)cyclobut -3-ene-1,2-dione (0.025 mmol) as catalyst, and the mixture was stirred at room temperature for 12 h (monitored by TLC). Then the solvent was distilled under vacuum, and the residue was purified by flash column chromatography (silica gel, Hex/AcOEt, v/v, 3:1) giving the title compound. Single crystals were obtained by slow evaporation of an ethyl acetate solution.