1-(5-Hy­droxy-2,2,8,8-tetra­methyl-2H,8H-pyrano[2,3-f]chromen-6-yl)ethanone

Sunayna Pawar; Adele Cheddie; Bernard Omondi; Neil Anthony Koorbanally

doi:10.1107/S160053681204055X

. 2012 Sep 29;68(Pt 10):o3048. doi: 10.1107/S160053681204055X

1-(5-Hydroxy-2,2,8,8-tetramethyl-2H,8H-pyrano[2,3-f]chromen-6-yl)ethanone

Sunayna Pawar ^a, Adele Cheddie ^a, Bernard Omondi ^a, Neil Anthony Koorbanally ^a,^*

PMCID: PMC3470397 PMID: 23125810

Abstract

In the title compound, C₁₈H₂₀O₄,the pyran ring of the chromene unit adopts a half-chair conformation. An intramolecular O—H⋯O hydrogen bond occurs. In the crystal, molecules are linked along the b axis by C—H⋯O hydrogen bonds.

Related literature

The title compound is a precursor in the synthesis of biologically active prenylated chalcones, see: Adler & Baldwin (2009 ▶); Lee & Li (2007 ▶); For related structures, see: Lee & Xia (2007 ▶); Mondal et al. (2007 ▶); Narender et al. (2005 ▶).

Experimental

Crystal data

C₁₈H₂₀O₄
M _r = 300.34
Triclinic,
a = 8.5039 (6) Å
b = 9.5370 (6) Å
c = 10.7859 (7) Å
α = 102.180 (3)°
β = 102.621 (3)°
γ = 110.671 (3)°
V = 757.86 (9) Å³
Z = 2
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 446 K
0.39 × 0.21 × 0.2 mm

Data collection

Bruker SMART APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.965, T _max = 0.982
17650 measured reflections
3770 independent reflections
3284 reflections with I > 2σ(I)
R _int = 0.018

Refinement

R[F ² > 2σ(F ²)] = 0.039
wR(F ²) = 0.119
S = 1.06
3770 reflections
205 parameters
H-atom parameters constrained
Δρ_max = 0.37 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT-Plus (Bruker, 2008 ▶); data reduction: SAINT-Plus and XPREP (Bruker, 2008 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 2012 ▶); software used to prepare material for publication: WinGX (Farrugia, 2012 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S160053681204055X/hg5251sup1.cif

e-68-o3048-sup1.cif^{(26.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681204055X/hg5251Isup2.hkl

e-68-o3048-Isup2.hkl^{(181KB, 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
O3—H3⋯O2	0.82	1.76	2.4897 (11)	148
C11—H11A⋯O2ⁱ	0.96	2.48	3.3829 (14)	156

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Symmetry code: (i) Inline graphic .

Acknowledgments

SP thanks the College of Agriculture, Engineering and Science of the University of KwaZulu-Natal for a doctoral bursary.

supplementary crystallographic information

Comment

The title compound (I), a pyranochromene acetophenone, was obtained as an intermediate in the synthesis of biologically active chalcones and flavanones (Adler & Baldwin, 2009; Lee & Li 2007; Lee & Xia, 2007). The pyranochromene skeleton is a core structure in various naturally active compounds (Adler and Baldwin 2009, Narender et al. 2005, Mondal et al. 2007). The efficient and concise synthesis of pyranochalcones was achieved from readily available 2,4,6-trihydroxyacetophenone. The key step in the synthetic strategy was a base catalyzed benzopyran formation. The crystal structure of the title compound (Fig. 1) has not been previously reported. One of the pyran rings of the chromene unit forms a half chair conformation [Q = 0.3846 (10) Å, θ = 112.81 (16)° and ψ = 142.65 (17) °]. The maximum displacement from the C1O1C13C14 plane are 0.684 Å for O16 and 0.275 Å for C15. In the crystal structure of the title compound, molecules are linked together by a C—H···O hydrogen bond along the crystallographic b axis (Table 1).

Experimental

To a one necked round bottom flask, 2,4,6-trihydroxyacetophenone (2.0 g, 0.0119 mol) and 2,3-dimethylbutenal (4.0 g, 0.0476 mol) was added. This was followed by the addition of pyridine (1.35 g) and the reaction mixture stirred for 24 h at 110°C. The reaction was monitored by TLC using EtOAc: Hexane (5:95, R_f = 0.6). After completion of the reaction, hydrochloric acid (30 ml) was added to neutralize the reaction and the mixture extracted with ethyl acetate (4 x 40 ml). The combined organic layer was dried over MgSO₄ and the solvent evaporated under reduced pressure. The residue was purified by column chromatography on silica gel using 100% hexane as the eluent to afford the pyranochromene as a yellow crystalline solid (2.58 g, yield 72.82%) with a melting point of 89–90 °C.

Recrystallization from hexane at room temperature afforded yellow crystals suitable for X-ray analysis.

¹H NMR (400 MHz, CDCl₃): δ (p.p.m.): 13.99 (1H, s, OH), 6.65 (1H, d, J = 10.08 Hz), 6.58 (1H, d, J = 10.08 Hz), 5.45 (1H, d, J = 10.08 Hz), 5.43 (1H, d, J = 10.08 Hz), 2.65 (3H, s), 1.49 (6H, s), 1.43 (6H, s).

¹³C NMR (100 MHz, CDCl₃): δ (p.p.m.): 203.2, 160.5, 156.6, 154.9, 125.3, 124.6, 116.4, 116.1, 105.7, 102.2, 102.1, 78.2, 78.1, 33.1, 28.5, 28.2.