(S)-(+)-1-(1-Naphthyl)-1-(2-thienylmethylene)ethylamine

The title chiral imine, C17H15NS, has been obtained via a direct synthesis route. The imine group displays the common E configuration, and is almost coplanar with the thiophene heterocycle; the dihedral angle between the C=N—C group and the thiophene ring is 5.1 (8)°. In contrast, the naphthyl group makes an angle of 83.79 (13)° with the thiophene ring. The observed solid-state molecular conformation is suitable for the use of this molecule as an N,S-bidentate Schiff base ligand. The molecular packing features double C—H⋯π interactions between naphthyl groups of neighboring molecules, which form chains in the [100] direction. The crystal structure is further stabilized by a short C—H⋯π contact involving the methyl group and one ring of a naphthyl group. The resulting two-dimensional network is completed by a weak intermolecular C—H(imine)⋯π(thiophene) interaction.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WN2331).
On the other hand, imines continue to attract much attention, mainly due to their versatile coordination behavior and the interesting properties of their metal complexes. Continuing our work on the synthesis of chiral imines (Tovar et al., 2007), we synthesized the title compound under solvent-free conditions (see Experimental) and report here its X-ray crystal structure.
The molecule is stabilized in the solid state as an E-trans aldimine ( Fig. 1), which has been shown to be the preferred configuration for imine systems derived from thiophene (Arjona et al., 1986). By conjugation, the imine group C6/N7/C8 is almost coplanar with the thiophene ring S1/C2/C3/C4/C5, with a dihedral angle of 5.1 (8)°. In contrast, the naphthyl group is almost normal to the thiophene ring, at 83.79 (13)°. The crystal packing features a number of intermolecular C-H···π contacts ( Fig. 2), the strongest involving the methyl group and a naphthyl group of a symmetry-related molecule. Naphthyl systems aggregate through double C-H···π interactions, forming chains along the [100] direction. The set of contacts results in a two-dimensional framework of efficiently stacked molecules.

Refinement
The title molecule crystallizes as thin plates, and the selected crystal was a poorly diffracting sample, limiting data resolution. All H atoms were placed in idealized positions and refined as riding on their carrier C atoms, with bond lengths fixed to 0.93 (aromatic CH), 0.96 (methyl CH 3 ), and 0.98 Å (methine CH). Isotropic displacement parameters were calculated as U iso (H) = 1.5U eq (carrier atom) for the methyl group and U iso (H) = 1.2U eq (carrier atom) otherwise. The absolute configuration was assigned by refinement of a Flack parameter, and agrees with the chirality expected from the synthetic route.
supplementary materials sup-2 Figures   Fig. 1. The title molecule with displacement ellipsoids for non-H atoms shown at the 30% probability level. Hydrogen atoms are shown as spheres of arbitrary radius.