2H,10H-1,4-Dioxepino[5′,6′:4,5]thieno[3,2-e][1,4]dioxepine-5,7(3H,9H)-dione

In the title compound, C₁₀H₈O₆S, which was synthesized by the intra­molecular cyclization of diethyl 3,4-bis­(2-hydroxy­ethoxy)thio­phene-2,5-dicarboxyl­ate, the thio­phene portion lies on a mirror plane. The crystal structure is stabilized by inter­molecular C—H...O hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• R factor = 0.066
• wR factor = 0.151
• Data-to-parameter ratio = 10.8

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S1. Comment

Heterocyclic compounds containing a 1,4-dioxepin-5-one ring (7-membered lactone) are expected to exhibit antibacterial activity (Ito et al., 1997; Rao, 1996). In addition, the compounds are of interest in terms of their polymerization abilities (Mathisen et al., 1989). The title compound, (I), is the first example of a thiophene derivative with two fused 1,4-dioxepin-5-one rings and its molecular and crystal structures are described here.

The compound (I) crystallizes in the Pnma space group with one molecule in the asymmetric unit (Fig. 1). The bond lengths and angles are within the normal ranges (Table 1). The molecule lies on the mirror plane except the O2, C6, C9 and C10 atoms and the H atoms bonded to the C atoms, which are crystallographically disordered about the plane over each site with 0.5 of occupancy.

In the crystal structure, the molecules stack along the b axis, where no molecular overlap was observed (Fig. 2). The distance between the molecular planes is 3.45 Å. As shown in Table 2 and Fig. 2, the stacks are linked by intermolecular C—H···O hydrogen bonds (Taylor & Kennard, 1982; Biradha et al., 1993; Batchelor et al., 2000).

Related literature

For the synthesis of the starting reagent, see: Halfpenny et al. (2000). For the antibacterial activity of 1,4-dioxepin-5-one compounds, see: Ito et al. (1997); Rao (1996). For their polymerization abilities, see: Mathisen et al. (1989). For related literature on molecular structures including a 1,4-dioxepin-5-one ring, see: Blaser & Stoeckli-Evans (1991); Brassy et al. (1977); Connolly et al. (1984); Lamothe & Fuchs (1993); Kawahara et al. (1988); Mulzer et al. (1996); Xu et al. (2000). For literature on C–H···O hydrogen bonds, see: Batchelor et al. (2000); Biradha et al. (1993); Taylor & Kennard (1982).

S2. Experimental

The title compound (I) was synthesized by the intramolecular cyclization of diethyl 3,4-bis(2-hydroxyethoxy)-2,5-thiophenedicarboxylate (II). Compound (II) was prepared as follows: A mixture of diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate (Halfpenny et al., 2000) (6.55 g, 25.2 mmol) and caesium fluoride (11.5 g, 75.7 mmol) in dry acetonitrile (150 ml) was stirred for 1 h under nitrogen. A solution of ethylene glycol monotosylate (12.0 g, 55.5 mmol) in acetonitrile (50 ml) was added dropwise and the mixture was refluxed for 62 h. After cooling, the reaction mixture was filtered and the filtrate was concentrated. The residue was dissolved in dichloromethane and the solution was washed with water. The organic solution was dried over Na₂SO₄ and concentrated. The resulting solid was chromatographed on alumina gel (from AcOEt to AcOEt/EtOH = 1:1) and silica gel (CH₂Cl₂/AcOEt = from 7:3 to 1:1) to give compound (II) (3.96 g, 45%) as colorless needles. Physical data for (II): m.p. 356–357 K; IR (KBr, cm^-1): 3306, 1715, 1493, 1370, 1296, 1256, 1076, 1047; ¹H NMR (CDCl₃, δ p.p.m.): 1.38 (t, J = 7.1 Hz, 6H), 3.83 (br s, 6H), 4.33–4.41 (m, 8H); ¹³C NMR (CDCl₃, δ p.p.m.): 14.2, 61.0, 61.9, 76.4, 120.2, 153.1, 160.9; MS (EI): m/z 348 (M⁺), 302, 286, 256, 212, 168. Anal. Calcd. For C₁₄H₂₀O₈S: C, 48.27; H, 5.79. Found: C, 48.28; H, 5.68.

Compound (I) was prepared as follows: A mixture of compound (II) (367 mg, 1.05 mmol) and p-toluenesulfonic acid (20 mg) in toluene was refluxed with a Dean-Stark apparatus for 20 h. The white precipitate was filtered to give compound (I) (245 mg, 91%). Physical data for (I): m.p. >573 K; IR (KBr, cm^-1): 1692, 1522, 1462, 1406, 1373, 1325, 1161, 1100, 1044, 1015, 968, 752; ¹H NMR (DMSO-d₆, δ p.p.m.): 4.64–4.69 (m, 8H); ¹³C NMR (DMSO-d₆, δ p.p.m.): 162.8, 145.6, 113.1, 71.4, 67.4; MS (EI): m/z 256 (M⁺), 212, 185. Anal. Calcd. For C₁₀H₈O₆S: C, 46.87; H, 3.15. Found: C, 46.90; H, 3.10. Colorless crystals of (I) suitable for X-ray analysis were grown from an acetone solution.

S3. Refinement

All H atoms were positioned geometrically refined using a riding model with C—H = 0.97 Å and with U_iso(H) = 1.2 times U_eq(C).

Computing details

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku,2001); cell refinement: CrystalClear (Molecular Structure Corporation & Rigaku, 2001); data reduction: TEXSAN (Molecular Structure Corporation & Rigaku, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms and H atoms are shown as small spheres of arbitrary radii. The crystallographically disordered atoms for O2, C6, C9 and C10 are omitted for clarity.
	Fig. 2. The packing diagram of (I), viewed along the b axis. Dashed lines indicate intermolecular C—H···O hydrogen bonds.

2H,10H-1,4-Dioxepino[5',6':4,5]thieno[3,2-e][1,4]dioxepine-5,7(3H,9H)-dione

Crystal data

C10H8O6S	Dx = 1.653 Mg m^−3
Mr = 256.22	Melting point > 573 K
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71070 Å
Hall symbol: -P 2ac 2n	Cell parameters from 2531 reflections
a = 20.301 (2) Å	θ = 3.0–27.5°
b = 6.9037 (8) Å	µ = 0.33 mm^−1
c = 7.3463 (8) Å	T = 296 K
V = 1029.6 (2) Å^3	Prism, colorless
Z = 4	0.25 × 0.25 × 0.10 mm
F(000) = 528

Data collection

Rigaku/MSC Mercury CCD diffractometer	1222 reflections with I > 2σ(I)
Radiation source: Rotating Anode	Rint = 0.038
Graphite Monochromator monochromator	θmax = 27.5°, θmin = 3.4°
Detector resolution: 14.6199 pixels mm^-1	h = −26→23
ϕ & ω scans	k = −8→8
7769 measured reflections	l = −6→9
1246 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.066	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.151	H-atom parameters constrained
S = 1.12	w = 1/[σ^2(Fo^2) + (0.1532P)^2 + 1.2875P] where P = (Fo^2 + 2Fc^2)/3
1246 reflections	(Δ/σ)max = 0.003
115 parameters	Δρmax = 0.24 e Å^−3
39 restraints	Δρmin = −0.28 e Å^−3

Special details

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
S1	0.03443 (5)	0.2500	0.59051 (10)	0.0415 (3)
O1	0.16771 (17)	0.2500	0.7229 (4)	0.0830 (12)
O2	0.22262 (18)	0.1835 (6)	0.4789 (5)	0.0626 (14)	0.50
O3	0.12917 (14)	0.2500	0.1296 (3)	0.0647 (9)
O4	−0.10643 (16)	0.2500	0.5961 (4)	0.0637 (8)
O5	−0.13039 (15)	0.2500	0.3096 (4)	0.0825 (12)
O6	0.00129 (15)	0.2500	0.0697 (3)	0.0829 (13)
C1	0.10475 (18)	0.2500	0.4587 (4)	0.0393 (7)
C2	0.08960 (18)	0.2500	0.2764 (4)	0.0436 (8)
C3	0.02063 (18)	0.2500	0.2444 (4)	0.0446 (8)
C4	−0.01558 (18)	0.2500	0.4004 (4)	0.0382 (7)
C5	0.1665 (2)	0.2500	0.5615 (5)	0.0551 (10)
C6	0.2204 (3)	0.1130 (11)	0.2935 (8)	0.0624 (15)	0.50
H6A	0.1911	0.0020	0.2890	0.075*	0.50
H6B	0.2641	0.0684	0.2601	0.075*	0.50
C7	0.1991 (2)	0.2500	0.1616 (6)	0.0687 (13)
H7A	0.2215	0.2234	0.0476	0.082*	0.50
H7B	0.2123	0.3784	0.2011	0.082*	0.50
C8	−0.08665 (19)	0.2500	0.4417 (5)	0.0452 (8)
C9	−0.1102 (3)	0.1692 (10)	0.1254 (7)	0.0619 (15)	0.50
H9A	−0.0861	0.0488	0.1399	0.074*	0.50
H9B	−0.1486	0.1453	0.0502	0.074*	0.50
C10	−0.0673 (3)	0.3208 (10)	0.0416 (7)	0.0599 (18)	0.50
H10A	−0.0769	0.3347	−0.0871	0.072*	0.50
H10B	−0.0738	0.4449	0.1008	0.072*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0580 (6)	0.0389 (5)	0.0277 (4)	0.000	0.0007 (3)	0.000
O1	0.077 (2)	0.135 (3)	0.0370 (14)	0.000	−0.0137 (14)	0.000
O2	0.0498 (19)	0.092 (4)	0.0462 (18)	−0.0018 (18)	−0.0067 (15)	0.0049 (18)
O3	0.0526 (16)	0.111 (3)	0.0304 (12)	0.000	0.0031 (11)	0.000
O4	0.0643 (18)	0.082 (2)	0.0452 (15)	0.000	0.0140 (13)	0.000
O5	0.0471 (17)	0.154 (4)	0.0467 (16)	0.000	0.0001 (13)	0.000
O6	0.0514 (17)	0.168 (4)	0.0289 (13)	0.000	−0.0037 (11)	0.000
C1	0.0520 (19)	0.0342 (17)	0.0317 (14)	0.000	−0.0017 (13)	0.000
C2	0.054 (2)	0.047 (2)	0.0293 (15)	0.000	0.0005 (13)	0.000
C3	0.050 (2)	0.054 (2)	0.0292 (15)	0.000	−0.0043 (13)	0.000
C4	0.0517 (18)	0.0304 (15)	0.0326 (15)	0.000	−0.0003 (13)	0.000
C5	0.057 (2)	0.070 (3)	0.0378 (18)	0.000	−0.0049 (16)	0.000
C6	0.046 (3)	0.084 (4)	0.057 (3)	0.004 (3)	0.004 (2)	−0.008 (3)
C7	0.051 (2)	0.107 (4)	0.048 (2)	0.000	0.0029 (18)	0.000
C8	0.052 (2)	0.0413 (19)	0.0425 (18)	0.000	0.0015 (15)	0.000
C9	0.055 (3)	0.080 (4)	0.051 (3)	0.003 (3)	−0.012 (2)	−0.011 (3)
C10	0.056 (3)	0.090 (5)	0.034 (2)	0.010 (3)	−0.011 (2)	0.004 (2)

Geometric parameters (Å, º)

S1—C1	1.725 (4)	C2—C3	1.420 (5)
S1—C4	1.727 (3)	C3—C4	1.361 (5)
O1—C5	1.186 (4)	C4—C8	1.474 (5)
O2—C6	1.447 (6)	C5—O2^i	1.370 (5)
O2—C5	1.370 (5)	C6—C7	1.421 (7)
O3—C2	1.345 (4)	C6—H6A	0.9700
O3—C7	1.439 (5)	C6—H6B	0.9700
O4—C8	1.204 (4)	C7—C6^i	1.421 (7)
O5—C8	1.315 (5)	C7—H7A	0.9700
O5—C9^i	1.520 (6)	C7—H7B	0.9700
O5—C9	1.520 (6)	C9—C10	1.494 (8)
O6—C3	1.342 (4)	C9—H9A	0.9700
O6—C10	1.491 (6)	C9—H9B	0.9700
O6—C10^i	1.491 (6)	C10—H10A	0.9700
C1—C2	1.375 (4)	C10—H10B	0.9700
C1—C5	1.463 (5)
C1—S1—C4	91.88 (16)	O2—C6—H6B	108.4
C6—O2—C5	120.2 (4)	C7—C6—H6B	108.4
C2—O3—C7	117.3 (3)	H6A—C6—H6B	107.5
C8—O5—C9^i	118.3 (3)	C6^i—C7—C6	83.4 (6)
C8—O5—C9	118.3 (3)	C6^i—C7—O3	114.3 (3)
C3—O6—C10	113.9 (3)	C6—C7—O3	114.3 (3)
C3—O6—C10^i	113.9 (3)	C6^i—C7—H7A	124.9
C2—C1—C5	134.0 (3)	C6—C7—H7A	108.7
C2—C1—S1	111.2 (3)	O3—C7—H7A	108.7
C5—C1—S1	114.8 (2)	C6—C7—H7B	108.7
O3—C2—C1	130.4 (3)	O3—C7—H7B	108.7
O3—C2—C3	117.2 (3)	H7A—C7—H7B	107.6
C1—C2—C3	112.4 (3)	O4—C8—O5	118.0 (4)
O6—C3—C4	130.3 (3)	O4—C8—C4	121.4 (3)
O6—C3—C2	116.5 (3)	O5—C8—C4	120.6 (3)
C4—C3—C2	113.2 (3)	C10—C9—O5	105.5 (4)
C3—C4—C8	134.6 (3)	C10—C9—H9A	110.6
C3—C4—S1	111.3 (3)	O5—C9—H9A	110.6
C8—C4—S1	114.1 (2)	C10—C9—H9B	110.6
O1—C5—C1	122.2 (4)	O5—C9—H9B	110.6
O1—C5—O2^i	115.2 (4)	H9A—C9—H9B	108.8
C1—C5—O2^i	119.0 (3)	O6—C10—C9	104.9 (4)
O1—C5—O2	115.2 (4)	O6—C10—H10A	110.8
C1—C5—O2	119.0 (3)	C9—C10—H10A	110.8
O2—C6—C7	115.3 (5)	O6—C10—H10B	110.8
O2—C6—H6A	108.4	C9—C10—H10B	110.8
C7—C6—H6A	108.4	H10A—C10—H10B	108.8
C4—S1—C1—C2	0.0	S1—C1—C5—O2^i	−157.5 (2)
C4—S1—C1—C5	180.0	C2—C1—C5—O2	−22.5 (2)
C7—O3—C2—C1	0.0	S1—C1—C5—O2	157.5 (2)
C7—O3—C2—C3	180.0	C6—O2—C5—O1	158.5 (4)
C5—C1—C2—O3	0.0	C6—O2—C5—C1	−0.5 (5)
S1—C1—C2—O3	180.0	C6—O2—C5—O2^i	−101.9 (4)
C5—C1—C2—C3	180.0	C5—O2—C6—C7	60.1 (6)
S1—C1—C2—C3	0.0	O2—C6—C7—C6^i	23.1 (6)
C10—O6—C3—C4	21.0 (3)	O2—C6—C7—O3	−90.6 (5)
C10^i—O6—C3—C4	−21.0 (3)	C2—O3—C7—C6^i	−46.9 (4)
C10—O6—C3—C2	−159.0 (3)	C2—O3—C7—C6	46.9 (4)
C10^i—O6—C3—C2	159.0 (3)	C9^i—O5—C8—O4	155.4 (3)
O3—C2—C3—O6	0.0	C9—O5—C8—O4	−155.4 (3)
C1—C2—C3—O6	180.0	C9^i—O5—C8—C4	−24.6 (3)
O3—C2—C3—C4	180.0	C9—O5—C8—C4	24.6 (3)
C1—C2—C3—C4	0.0	C3—C4—C8—O4	180.0
O6—C3—C4—C8	0.0	S1—C4—C8—O4	0.0
C2—C3—C4—C8	180.0	C3—C4—C8—O5	0.0
O6—C3—C4—S1	180.0	S1—C4—C8—O5	180.0
C2—C3—C4—S1	0.0	C8—O5—C9—C10	−75.3 (4)
C1—S1—C4—C3	0.0	C9^i—O5—C9—C10	27.0 (4)
C1—S1—C4—C8	180.0	C3—O6—C10—C9	−68.2 (4)
C2—C1—C5—O1	180.0	C10^i—O6—C10—C9	30.7 (4)
S1—C1—C5—O1	0.0	O5—C9—C10—O6	101.2 (4)
C2—C1—C5—O2^i	22.5 (2)

Symmetry code: (i) x, −y+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C6—H6A···O4^ii	0.97	2.59	3.506 (7)	158
C10—H10A···O4^iii	0.97	2.47	3.403 (6)	160
C6—H6B···O5^iv	0.97	2.53	3.262 (7)	132
C6—H6B···O1^v	0.97	2.61	3.422 (7)	141

Symmetry codes: (ii) −x, y−1/2, −z+1; (iii) x, y, z−1; (iv) x+1/2, −y+1/2, −z+1/2; (v) −x+1/2, −y, z−1/2.