Ethyl (E)-2-(2,7-dimethyl-5-oxo-4H,5H-pyrano[4,3-b]pyran-4-yl­idene)acetate

Bassou, O.; Chicha, H.; Bouissane, L.; Rakib, E.M.; Saadi, M.; El Ammari, L.

doi:10.1107/S2414314617002085

organic compounds

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ISSN: 2414-3146

Volume 2| Part 2| February 2017| x170208

https://doi.org/10.1107/S2414314617002085

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Ethyl (E)-2-(2,7-dimethyl-5-oxo-4H,5H-pyrano[4,3-b]pyran-4-ylidene)acetate

Oulemda Bassou,^a ^* Hakima Chicha,^a Latifa Bouissane,^a El Mostapha Rakib,^a Mohamed Saadi ^b and Lahcen El Ammari ^b

^aLaboratoire de Chimie Organique et Analytique, Université Sultan Moulay Slimane, Faculté des Sciences et Techniques, Béni-Mellal, BP 523, Morocco, and ^bLaboratoire de Chimie du Solide Appliquée, Faculty of Sciences, Mohammed V University in Rabat, Avenue Ibn Battouta, BP 1014, Rabat, Morocco
^*Correspondence e-mail: o_bassou@yahoo.com

Edited by H. Stoeckli-Evans, University of Neuchâtel, Switzerland (Received 25 January 2017; accepted 8 February 2017; online 14 February 2017)

In the title compound, C₁₄H₁₄O₅, the two heterocyclic rings are coplanar (r.m.s. deviation = 0.008 Å), with the largest deviation from the mean plane being 0.012 (1) Å. The mean plane through the acetate group is inclined slightly with respect to the oxopyrano[4,3-b]pyran-4-yl system, as indicated by the dihedral angle of 1.70 (7)° between them. Two intramolecular hydrogen bonds, completing S(6) ring motifs, are observed in the molecule. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds involving the same acceptor atom, forming chains propagating along the c-axis direction and enclosing R₂¹(6) ring motifs. The chains are linked via offset π–π interactions [intercentroid distance = 3.622 (1) Å], involving inversion-related oxopyrano[4,3-b]pyran-4-yl ring systems, forming slabs parallel to the bc plane.

Keywords: crystal structure; oxopyrano[4,3-b]pyran-4-ylidene; heterocyclic compounds; C—H⋯O hydrogen bonding; offset π–π interactions.

CCDC reference: 1531805

Structure description

Pyrones are among the most important heterocyclic structures in medicinal chemistry and specifically, 2-pyrones can be found in a wide range of medicinally significant natural products (Lee et al., 2000 ; Fairlamb et al., 2004 ; McGlacken & Fairlamb, 2005 ; Perchellet et al., 1998 ; Defant et al., 2015 ). As heterocyclic aromatic enols, they have a high acidity and dense functionality, which leads to a diverse reactivity profile. This means that 4-hydroxy-2-pyrones are also useful precursors to a number of other structural units and versatile intermediates in organic synthesis (Burns et al., 2014 ; Aggarwal et al., 2013 ).

The molecule of the title compound is build up from a bicyclic oxopyrano[4,3-b]pyran-4-ylidene ring system linked to two methyl groups and one acetate group, as shown in Fig. 1. The fused heterocyclic rings are virtually coplanar with the maximum deviation from the mean plane being 0.012 (2) Å for atom C9. The oxopyrano[4,3-b]pyran-4-yl system makes a dihedral angle of 1.70 (7)° with the mean plane through the acetate group. Two intramolecular C—H⋯O contacts, enclosing S(6) ring motifs, are observed in the molecule (Fig. 1 and Table 1).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯O4	0.93	2.20	2.883 (2)	130
C6—H6⋯O2	0.93	2.24	2.894 (2)	127
C12—H12⋯O4ⁱ	0.93	2.59	3.283 (2)	132
C13—H13C⋯O4ⁱ	0.96	2.59	3.398 (2)	143
Symmetry code: (i) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Figure 1
A view of the molecular structure of the title compound, showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The intramolecular C—H⋯O contacts are shown as dashed lines (see Table 1

In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds involving the same acceptor atom (see Table 1), forming chains propagating along the c-axis direction and enclosing $[R_{2}^{1}]$ (6) ring motifs (Fig. 2). The chains are linked via offset π–π interactions involving inversion-related oxopyrano[4,3-b]pyran-4-yl ring systems, [intercentroid distance = 3.622 (1) Å], forming slabs parallel to the bc plane (Fig. 3).

Figure 2
A partial view, normal to (110), of the crystal packing for the title compound, with hydrogen bonds shown as dashed lines (see Table 1

; only H atoms H4, H6, H12 and H13C have been included).

Figure 3
A view along the c axis of the crystal packing for the title compound, with the hydrogen bonds shown as dashed lines (see Table 1

; only H atoms H4, H6, H12 and H13C have been included).

Synthesis and crystallization

To a solution of 6-aminouracil (1 mmol) in 25 ml of ethanol, 4-hydroxy-6-methyl-2-pyrone (1.1 mmol) and drops of triethylamine were added. The mixture was refluxed for 8 h. After cooling to room temperature, the solvent was removed under reduced pressure. The crude product was purified on silica gel using hexane:ethyl acetate (2/8) as eluent. The title compound was recrystallized from ethanol giving colourless block-like crystals (yield: 54%, m.p. 376 K). It should be noted that in the reaction of 6-aminouracil with 4-hydroxy-6-methyl-2-pyrone, under reflux of ethanol in the presence of Et3N, we observed another competitive reaction between two molecules of 4-hydroxy-6 -methyl-2-pyrone, this reaction is kinetically favored over the first reaction. Details are given in the Supporting information.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₄H₁₄O₅
M_r	262.25
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	9.5679 (12), 11.4330 (13), 12.7993 (15)
β (°)	108.257 (4)
V (Å³)	1329.6 (3)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.10
Crystal size (mm)	0.32 × 0.26 × 0.21

Data collection
Diffractometer	Bruker X8 APEX
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.663, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	16353, 2939, 1909
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.641

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.043, 0.137, 1.03
No. of reflections	2939
No. of parameters	180
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.17, −0.15
Computer programs: APEX2 and SAINT (Bruker, 2009 ), SHELXT2014 (Sheldrick, 2015a ), SHELXL2014 (Sheldrick, 2015b ), ORTEP-3 for Windows (Farrugia, 2012 ), Mercury (Macrae et al., 2008 ), PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1531805

Crystal structure: contains datablocks I, Global. DOI: https://doi.org/10.1107/S2414314617002085/su4128sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617002085/su4128Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314617002085/su4128Isup3.cml

Supporting information file. DOI: https://doi.org/10.1107/S2414314617002085/su4128sup4.pdf

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Ethyl (E)-2-(2,7-dimethyl-5-oxo-4H,5H-pyrano[4,3-b]pyran-4-ylidene)acetate top

Crystal data top

C₁₄H₁₄O₅	D_x = 1.310 Mg m⁻³
M_r = 262.25	Melting point: 376 K
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.5679 (12) Å	Cell parameters from 2939 reflections
b = 11.4330 (13) Å	θ = 2.5–27.1°
c = 12.7993 (15) Å	µ = 0.10 mm⁻¹
β = 108.257 (4)°	T = 296 K
V = 1329.6 (3) Å³	Block, colourless
Z = 4	0.32 × 0.26 × 0.21 mm
F(000) = 552

Data collection top

Bruker X8 APEX diffractometer	2939 independent reflections
Radiation source: fine-focus sealed tube	1909 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.037
φ and ω scans	θ_max = 27.1°, θ_min = 2.5°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −12→12
T_min = 0.663, T_max = 0.746	k = −14→14
16353 measured reflections	l = −13→16

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.137	H-atom parameters constrained
S = 1.03	w = 1/[σ²(F_o²) + (0.0699P)² + 0.1184P] where P = (F_o² + 2F_c²)/3
2939 reflections	(Δ/σ)_max < 0.001
180 parameters	Δρ_max = 0.17 e Å⁻³
0 restraints	Δρ_min = −0.15 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.7176 (3)	0.4822 (2)	1.10578 (18)	0.1053 (9)
H1A	0.7896	0.5034	1.1742	0.158*
H1B	0.6384	0.5376	1.0884	0.158*
H1C	0.6801	0.4055	1.1122	0.158*
C2	0.7864 (2)	0.4820 (2)	1.01765 (16)	0.0901 (7)
H2A	0.8250	0.5590	1.0105	0.108*
H2B	0.8670	0.4263	1.0345	0.108*
C3	0.7183 (2)	0.43027 (15)	0.82769 (14)	0.0584 (5)
C4	0.59172 (17)	0.40172 (14)	0.73274 (13)	0.0523 (4)
H4	0.5000	0.3988	0.7433	0.063*
C5	0.59770 (16)	0.37903 (12)	0.62997 (12)	0.0442 (4)
C6	0.73205 (17)	0.38065 (13)	0.60097 (14)	0.0496 (4)
H6	0.8198	0.3960	0.6563	0.060*
C7	0.73778 (16)	0.36155 (14)	0.50021 (14)	0.0508 (4)
C8	0.48137 (16)	0.33460 (12)	0.43348 (13)	0.0453 (4)
C9	0.46732 (15)	0.35306 (12)	0.53543 (12)	0.0420 (4)
C10	0.31964 (17)	0.34808 (14)	0.54336 (13)	0.0488 (4)
C11	0.22563 (17)	0.30720 (14)	0.34851 (13)	0.0515 (4)
C12	0.35992 (17)	0.31137 (14)	0.33862 (14)	0.0519 (4)
H12	0.3739	0.2993	0.2707	0.062*
C13	0.08513 (19)	0.2864 (2)	0.26002 (16)	0.0752 (6)
H13A	0.0281	0.3571	0.2461	0.130 (10)*
H13B	0.0310	0.2259	0.2824	0.109 (8)*
H13C	0.1052	0.2627	0.1942	0.100 (7)*
C14	0.8690 (2)	0.36234 (18)	0.46180 (18)	0.0702 (6)
H14A	0.8813	0.2865	0.4338	0.109 (8)*
H14B	0.9548	0.3815	0.5222	0.100 (7)*
H14C	0.8558	0.4196	0.4046	0.102 (8)*
O1	0.67347 (14)	0.44936 (12)	0.91578 (10)	0.0756 (4)
O2	0.84654 (14)	0.43692 (14)	0.83266 (11)	0.0822 (5)
O3	0.61171 (11)	0.33840 (10)	0.41328 (9)	0.0557 (3)
O4	0.28225 (13)	0.36313 (13)	0.62435 (10)	0.0714 (4)
O5	0.20544 (11)	0.32427 (10)	0.44793 (9)	0.0546 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.110 (2)	0.129 (2)	0.0675 (13)	0.0096 (16)	0.0138 (14)	−0.0315 (14)
C2	0.0758 (15)	0.1147 (18)	0.0611 (12)	0.0024 (13)	−0.0055 (11)	−0.0259 (12)
C3	0.0485 (11)	0.0619 (11)	0.0556 (10)	0.0028 (8)	0.0030 (8)	−0.0001 (8)
C4	0.0406 (9)	0.0584 (10)	0.0531 (10)	−0.0007 (7)	0.0079 (7)	0.0046 (7)
C5	0.0348 (8)	0.0411 (8)	0.0515 (9)	0.0014 (6)	0.0061 (7)	0.0063 (6)
C6	0.0318 (8)	0.0524 (9)	0.0573 (10)	0.0009 (6)	0.0034 (7)	0.0027 (7)
C7	0.0304 (8)	0.0516 (9)	0.0676 (11)	0.0000 (6)	0.0111 (8)	−0.0013 (8)
C8	0.0329 (8)	0.0445 (8)	0.0577 (10)	−0.0009 (6)	0.0132 (7)	−0.0020 (7)
C9	0.0326 (8)	0.0417 (8)	0.0484 (9)	0.0006 (6)	0.0079 (7)	0.0046 (6)
C10	0.0350 (8)	0.0586 (10)	0.0495 (9)	−0.0038 (7)	0.0084 (8)	0.0085 (7)
C11	0.0386 (9)	0.0580 (10)	0.0532 (9)	−0.0056 (7)	0.0075 (7)	−0.0067 (7)
C12	0.0400 (9)	0.0636 (10)	0.0510 (9)	−0.0047 (7)	0.0125 (7)	−0.0103 (7)
C13	0.0416 (10)	0.1101 (17)	0.0657 (12)	−0.0123 (11)	0.0050 (9)	−0.0200 (11)
C14	0.0401 (10)	0.0861 (15)	0.0874 (14)	−0.0025 (9)	0.0243 (10)	−0.0080 (12)
O1	0.0609 (8)	0.1019 (10)	0.0552 (7)	0.0007 (7)	0.0055 (6)	−0.0196 (7)
O2	0.0457 (8)	0.1220 (12)	0.0674 (9)	−0.0020 (7)	0.0014 (7)	−0.0103 (8)
O3	0.0336 (6)	0.0732 (8)	0.0607 (7)	−0.0042 (5)	0.0151 (5)	−0.0125 (5)
O4	0.0439 (7)	0.1199 (11)	0.0522 (7)	−0.0059 (7)	0.0176 (6)	0.0078 (7)
O5	0.0321 (6)	0.0744 (8)	0.0546 (7)	−0.0077 (5)	0.0097 (5)	−0.0009 (5)

Geometric parameters (Å, º) top

C1—C2	1.473 (3)	C7—C14	1.485 (2)
C1—H1A	0.9600	C8—O3	1.3513 (18)
C1—H1B	0.9600	C8—C9	1.369 (2)
C1—H1C	0.9600	C8—C12	1.418 (2)
C2—O1	1.458 (2)	C9—C10	1.449 (2)
C2—H2A	0.9700	C10—O4	1.2102 (19)
C2—H2B	0.9700	C10—O5	1.3869 (18)
C3—O2	1.211 (2)	C11—C12	1.331 (2)
C3—O1	1.344 (2)	C11—O5	1.3596 (19)
C3—C4	1.459 (2)	C11—C13	1.481 (2)
C4—C5	1.359 (2)	C12—H12	0.9300
C4—H4	0.9300	C13—H13A	0.9600
C5—C6	1.446 (2)	C13—H13B	0.9600
C5—C9	1.471 (2)	C13—H13C	0.9600
C6—C7	1.326 (2)	C14—H14A	0.9600
C6—H6	0.9300	C14—H14B	0.9600
C7—O3	1.3864 (18)	C14—H14C	0.9600

C2—C1—H1A	109.5	C9—C8—C12	123.09 (14)
C2—C1—H1B	109.5	C8—C9—C10	116.72 (14)
H1A—C1—H1B	109.5	C8—C9—C5	120.27 (13)
C2—C1—H1C	109.5	C10—C9—C5	123.00 (14)
H1A—C1—H1C	109.5	O4—C10—O5	114.81 (14)
H1B—C1—H1C	109.5	O4—C10—C9	127.65 (15)
O1—C2—C1	107.53 (19)	O5—C10—C9	117.54 (14)
O1—C2—H2A	110.2	C12—C11—O5	120.55 (14)
C1—C2—H2A	110.2	C12—C11—C13	127.24 (17)
O1—C2—H2B	110.2	O5—C11—C13	112.20 (14)
C1—C2—H2B	110.2	C11—C12—C8	118.81 (16)
H2A—C2—H2B	108.5	C11—C12—H12	120.6
O2—C3—O1	122.03 (16)	C8—C12—H12	120.6
O2—C3—C4	128.38 (18)	C11—C13—H13A	109.5
O1—C3—C4	109.59 (15)	C11—C13—H13B	109.5
C5—C4—C3	124.97 (16)	H13A—C13—H13B	109.5
C5—C4—H4	117.5	C11—C13—H13C	109.5
C3—C4—H4	117.5	H13A—C13—H13C	109.5
C4—C5—C6	123.81 (14)	H13B—C13—H13C	109.5
C4—C5—C9	123.55 (14)	C7—C14—H14A	109.5
C6—C5—C9	112.62 (14)	C7—C14—H14B	109.5
C7—C6—C5	123.96 (15)	H14A—C14—H14B	109.5
C7—C6—H6	118.0	C7—C14—H14C	109.5
C5—C6—H6	118.0	H14A—C14—H14C	109.5
C6—C7—O3	121.42 (14)	H14B—C14—H14C	109.5
C6—C7—C14	128.16 (16)	C3—O1—C2	116.73 (16)
O3—C7—C14	110.42 (15)	C8—O3—C7	118.41 (12)
O3—C8—C9	123.32 (14)	C11—O5—C10	123.28 (13)
O3—C8—C12	113.58 (14)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···O4	0.93	2.20	2.883 (2)	130
C6—H6···O2	0.93	2.24	2.894 (2)	127
C12—H12···O4ⁱ	0.93	2.59	3.283 (2)	132
C13—H13C···O4ⁱ	0.96	2.59	3.398 (2)	143

Symmetry code: (i) x, −y+1/2, z−1/2.

Acknowledgements

The authors thank the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements.

Funding information

Funding for this research was provided by: University Sultan Moulay Slimane, Beni-Mellal, Morocco

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