2-(4-Methoxyphenoxy)-6-methyl-3-oxo-3,6-dihydro-2H-pyran-4-yl benzoate

Shi-qiang Yan; Xiao-mei Liang; Jian-jun Zhang; Dao-quan Wang

doi:10.1107/S1600536809004231

. 2009 Feb 25;65(Pt 3):o586. doi: 10.1107/S1600536809004231

2-(4-Methoxyphenoxy)-6-methyl-3-oxo-3,6-dihydro-2H-pyran-4-yl benzoate

Shi-qiang Yan ^a, Xiao-mei Liang ^a, Jian-jun Zhang ^a,^*, Dao-quan Wang ^a

PMCID: PMC2968613 PMID: 21582241

Abstract

The title compound, C₂₀H₁₈O₆, has been synthesized from 4-methoxyphenyl 3-O-benzoyloxy-α-l-rhamnopyranoside by oxidation on treatment with pyridinium dichromate in the presence of acetic anhydride. In the molecule, the pyran ring adopts an envelope conformation with the O atom at the flap position. Weak intermolecular C—H⋯O hydrogen bonding is present in the crystal structure.

Related literature

For general background to enolone derivatives, see: Schmidt et al. (1954 ▶); Hodges et al. (1963 ▶); Bevan et al. (1963 ▶); Ripperger & Seifert (1975 ▶); Yan et al. (2008 ▶).

Experimental

Crystal data

C₂₀H₁₈O₆
M _r = 354.34
Orthorhombic,
a = 8.5906 (17) Å
b = 11.594 (2) Å
c = 17.404 (4) Å
V = 1733.4 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 173 (2) K
0.80 × 0.72 × 0.40 mm

Data collection

Rigaku R-Axis Rapid IP are-detector diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T _min = 0.924, T _max = 0.961
3953 measured reflections
2262 independent reflections
1752 reflections with I > 2σ(I)
R _int = 0.015

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.055
S = 0.87
2262 reflections
236 parameters
H-atom parameters constrained
Δρ_max = 0.17 e Å⁻³
Δρ_min = −0.24 e Å⁻³

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

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809004231/xu2467sup1.cif

e-65-0o586-sup1.cif^{(20.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809004231/xu2467Isup2.hkl

e-65-0o586-Isup2.hkl^{(111.2KB, 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
C15—H15A⋯O6ⁱ	0.95	2.42	3.343 (2)	163

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank the Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry (No. 21168020) and the Doctoral Program Foundation of Institutions of Higher Education of China (No. 20070019072) for support.

supplementary crystallographic information

Comment

The enolone structural unit is often present in nature products, such as brevifolic acid, a constituent of the ellagitannins (Schmidt et al., 1954), meliacinslike cedrelone and anthothecol (Hodges et al., 1963; Bevan et al., 1963) or triterpenoids of the elaterin type, which are widely distributed in cucurbitaceous and cruciferous plants (Ripperger & Seifert, 1975). In a continuation of our search for alcohol oxidation (Yan et al., 2008), herein we present the crystal structure of the title compound, which was produced by oxidation with PDC and acetic anhydride.

In the molecule of the title compound (Fig. 1), the pyran ring conformation can be described as an envelope, with C1/C2/C3/C4/C5 lying almost on the same plane and O1 deviating from this mean plane. The terminal benzene rings of the molecule are nearly perpendicular to each other with a dihedral angle of 83.6 (1)°. The weak intermolecular C—H···O hydrogen bonding presents in the crystal structure (Table 1).

Experimental

A mixture of 4-methoxyphenyl 3-O-benzoyloxy-a-L-rhamnopyranoside (3.74 g, 10 mmol), pyridinium dichromate (4.60 g, 12 mmol), and acetic anhydride (5.68 ml, 60 mmol) in CH₂Cl₂ (40 ml) was stirred at reflux for 8 h, at the end of which time TLC (4:1 petroleumether–EtOAc) indicated that the reaction was complete. After direct concentration of the reaction mixture, the dark brown residue was diluted with EtOAc (60 ml) and the solution was passed through a short (5–10 cm) silica-gel column. The column was eluted with EtOAc and the eluents were concentrated and coevaporated with toluene. The residue was subjected to silica-gel column chromatography again (4:1 petroleum ether–EtOAc) to give the title compound (2.48 g, 70%). Single crystals suitable for X-ray measurements were obtained by recrystallization from 8:1 petroleumether–EtOAc at room temperature.