4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-5-yl)aniline

In the title molecule, C12H11NO2S, the dioxane-type ring adopts a half-chair conformation. The thiophene ring forms a dihedral angle of 12.53 (6)° with the benzene ring. In the crystal, N—H⋯O, hydrogen bonds link molecules, forming chains along the c-axis direction. A weak intramolecular C—H⋯O hydrogen bond is observed.


Comment
The title compound is composed of an aniline moiety with a 3,4-ethylenedioxythiophene group appended at the 4position, see Fig. 1. It has been used in the development of π-conjugated oligomers, which have low HOMO-LUMO gaps and are easily oxidized at low potentials, making them potential materials for photovoltaics and other optoelectronic applications (Trippé-Allard & Lacroix, 2013). The geometry of the ethylenedioxythiophene moiety is similar to other ethylenedioxythiophene containing compounds reported in the literature, which includes the six-membered dioxane-type ring in the half-chair conformation (Chen et al., 2011;Sotzing & Reynolds, 1996;Riehn et al., 2000). The dihedral angle between the thiophene and benzene rings is 12.53 (6)°. In the crystal, N1-H10A···O1 i hydrogen bonds link molecules into chains along the c axis (Fig. 2). A weak intramolecular C-H···O hydrogen bond is also observed.
The isolated yellow solid was added to a round bottom and dissolved in tetrahydrofuran (THF). Charcoal (8.39 g) and 5 ml of H 2 O was added and the mixture was heated to 323 K. Sodium borohydride (2.66 g, 70.5 mmol) was added in four portions over 1 hr. The reaction was heated for an additional 30 min after the last addition. The mixture was cooled to room temp. and filtered, washing with THF. The solution was concentrated then re-dissolved in CH 2 Cl 2 and washed with H 2 O. The organic layer was concentrated to a third the original volume and mixed with an equal volume of hexanes. The solution was left standing overnight at 273 K and the orange crystals that precipitated were collected by vacuum filtration

Refinement
The amine H atoms were located in a difference Fourier map and both positional and isotropic displacement parameters were refined. All other H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.97 Å and with U iso (H) = 1.2 times U eq (C).  Molecular structure of title compound. Ellipsoids are drawn at the 50% probability level.

Figure 2
Part of the crystal structure viewed along the b axis. Thin black lines indicate N-H···O hydrogen bonds.

4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-5-yl)aniline
Crystal data C 12 H 11 NO 2 S M r = 233.28 Orthorhombic, P2 1 2 1 2 1 Hall symbol: P 2ac 2ab a = 6.9117 (6)  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.