Diethyl 2,3-dihydro­thieno[3,4-b]-1,4-dioxine-5,7-dicarboxyl­ate

Katsuhiko Ono; Masaaki Tomura; Katsuhiro Saito

doi:10.1107/S1600536808000937

. 2008 Jan 18;64(Pt 2):o468. doi: 10.1107/S1600536808000937

Diethyl 2,3-dihydrothieno[3,4-b]-1,4-dioxine-5,7-dicarboxylate

Katsuhiko Ono ^a,^*, Masaaki Tomura ^b, Katsuhiro Saito ^a

PMCID: PMC2960460 PMID: 21201494

Abstract

The title compound, C₁₂H₁₄O₆S, is a dicarboxylic acid diethyl ester of 3,4-ethylenedioxythiophene, which is a component of electrically conductive poly(3,4-ethylenedioxythiophene) (PEDOT). The ethylene group is disordered over two sites with occupancy factors 0.64 and 0.36. Both the carbonyl groups are coplanar with the thiophene ring. The molecules form centrosymmetric dimers with an R ₂ ²(12) coupling by intermolecular C—H⋯O hydrogen bonds [3.333 (5) Å] at the ethoxycarbonyl groups. The dimer units are arranged to form a ribbon-like molecular sheet.

Related literature

The title compound was synthesized as a precursor of 3,4-ethylenedioxythiophene, which is polymerized to afford PEDOT (Groenendaal et al., 2000 ▶; Pei et al., 1994 ▶). Synthetic methods for the title compound have been reported by: Coffey et al. (1996 ▶); Kumar et al. (1998 ▶); Zong et al. (2002 ▶); Caras-Quintero & Bäuerle (2002 ▶). For literature on related molecular structures, including a 3,4-ethylenedioxythiophene ring system, see: Sotzing et al. (1996 ▶); Abboud et al. (1998 ▶); Kumar et al. (1998 ▶). For related literature, see: Bernstein et al. (1995 ▶); Allen et al. (1987 ▶).

Experimental

Crystal data

C₁₂H₁₄O₆S
M _r = 286.30
Triclinic,
a = 4.6805 (8) Å
b = 8.3673 (17) Å
c = 17.351 (3) Å
α = 94.294 (7)°
β = 92.024 (9)°
γ = 105.641 (9)°
V = 651.4 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.27 mm⁻¹
T = 295 (1) K
0.60 × 0.10 × 0.08 mm

Data collection

Rigaku/MSC Mercury CCD diffractometer
Absorption correction: none
5181 measured reflections
2899 independent reflections
2300 reflections with I > 2σ(I)
R _int = 0.036

Refinement

R[F ² > 2σ(F ²)] = 0.069
wR(F ²) = 0.176
S = 1.11
2899 reflections
193 parameters
H-atom parameters constrained
Δρ_max = 0.55 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: CrystalClear (Rigaku/MSC, 2001 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808000937/hg2368sup1.cif

e-64-0o468-sup1.cif^{(18.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808000937/hg2368Isup2.hkl

e-64-0o468-Isup2.hkl^{(142.4KB, 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
C9—H9B⋯O3ⁱ	0.96	2.66	3.333 (5)	127
C9—H9A⋯O3ⁱⁱ	0.96	2.62	3.523 (7)	157
C6B—H6B1⋯O5ⁱⁱⁱ	0.97	2.68	3.233 (12)	117

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

This work was supported by a Grant-in-Aid (grant No. 19550034) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. The authors thank the Instrument Center of the Institute for Molecular Science for the X-ray structure analysis.

supplementary crystallographic information

Comment

The title compound (I) has been prepared as a precursor of 3,4-ethylenedioxythiophene (Coffey et al., 1996; Kumar et al., 1998; Zong et al., 2002; Caras-Quintero & Bäuerle, 2002), which is polymerized by oxidizing agents to afford poly(3,4-ethylenedioxythiophene) (PEDOT). PEDOT shows high electrical conductivities and high stabilities in the oxidized states. Furthermore, the thin films of oxidized PEDOT are almost transparent. Therefore, these are used for organic electrodes in the study of electronic devices (Groenendaal et al., 2000; Pei et al., 1994). With regard to the hole-transporting abilities, the arrangement of 3,4-ethylenedioxythiophene units in film has attracted considerable attention. A few crystal structures including a 3,4-ethylenedioxythiophene ring system were reported (Sotzing et al., 1996; Abboud et al., 1998; Kumar et al., 1998). In this paper, we report the crystal structure of compound (I) that is a dicarboxylic acid diethyl ester of 3,4-ethylenedioxythiophene.

The compound (I) crystallizes in the P1 space group. The molecular structure is shown in Fig. 1. The ethylene moiety is disordered over two sites (O1—C5A—C6A—O2 and O1—C5B—C6B—O2) with occupancies of 0.36:0.64. The bond lengths and angles are all within expected ranges (Allen et al., 1987). Both the carbonyl moieties are planar to the thiophene ring. The molecules form a centrosymmetric dimer with a graph-set motif (Bernstein et al., 1995) of R₂²(12) by intermolecular C–H···O hydrogen bonds at the ethoxycarbonyl groups [C9–H9B···O3(–x + 3, –y, –z): 3.333 (5) Å]. The dimer units are arranged to form a ribbon-like molecular sheet along the b axis, as shown in Fig. 2. The ribbon-like molecular sheets stack to form a layer structure (Fig. 3).

Experimental

The title compound (I) was prepared as follows: A solution of diethyl 3,4-dihydroxythiophene-2,5-dicarboxylate (3.12 g, 12 mmol) and caesium fluoride (7.26 g, 48 mmol) in dry acetonitrile (200 ml) was stirred for 1 h under nitrogen. After addition of a solution of ethylene di(p-toluenesulfonate) (5.55 g, 15 mmol) in dry acetonitrile (100 ml), the reaction mixture was refluxed for 48 h. The reaction mixture was filtered and the precipitate was washed with acetonitrile. The filtrate was concentrated and the residue was chromatographed on alumina gel (CH₂Cl₂) and silica gel (CH₂Cl₂) to afford the compound of (I) (2.38 g, 69%) as colorless needles. Physical data for (I): m.p. 424–425 K; IR (KBr, cm^-1) 2998, 1698, 1454, 1377, 1302, 1098; ¹H NMR (CDCl₃, δ p.p.m): 1.37 (t, J = 7.1 Hz, 6H), 4.35 (q, J = 7.1 Hz, 4H), 4.40 (s, 4H); ¹³C NMR (CDCl₃, δ p.p.m): 14.2, 61.3, 64.7, 111.8, 144.9, 160.7; MS (EI): m/z 286 (M⁺), 241, 213, 169. Anal. Calcd for C₁₂H₁₄O₆S: C, 50.34; H, 4.93. Found: C, 50.50; H, 4.96. Colorless crystals of (I) suitable for X-ray analysis were obtained from a methanol solution.