Crystal structure of (E)-2-{[(6-methoxy-1,3-benzothiazol-2-yl)imino]methyl}phenol

The title compound crystallizes with two molecules in the asymmetric unit (Z′ = 2) which are linked into dimers by (20) C—H⋯O interactions. These dimers are further linked into sheets in the ab plane by weak intermolecular C—H⋯N interactions.


Chemical context
A wide range of biological activities have been attributed to aminothiazoles and compounds having similar structures (Tahiliani et al., 2003) and they have many applications in both human and veterinary medicine (Smith et al., 1999;Sarhan et al., 2010). Certain 2-aminobenzothiazole derivatives act on the central nervous system (Funderburk et al., 1953), possess antimicrobial (Murhekar & Khadsan, 2010;Ravi et al., 2014), antifungal (Catalano et al., 2013) and antibacterial properties (Asiri et al., 2013), serve as selective receptors for anion sensing (Hijji & Wairia, 2005), are active in corrosion inhibition (Quraishi et al., 1997;Rawat & Quraishi, 2003) and act as plant-growth regulators (Mahajan et al., 2013). In addition, some metal complexes of Schiff bases of 2-aminobenzothiazole derivatives have potent antibacterial properties (Sharma et al., 2002;Song et al., 2010). Among antitumor agents discovered in recent years, the identification of various 2-(4aminophenyl)benzothiazoles as potent and selective antitumor drugs against breast, ovarian, colon and renal cell lines has stimulated remarkable interest (Usman et al., 2003;Shi et al., 1996;Havrylyuk et al. 2010) in this class of compound from both a synthetic, and particularly, a structural point of view. Aminothiazole Schiff bases have been prepared as intermediate ligands and for complexation with various metals (Liang et al.,1999;Liu et al., 2009)

Structural commentary
The title compound, C 15 H 12 N 2 O 2 S, crystallizes in the orthorhombic space group, Pna2 1 , with two molecules (A and B) in the asymmetric unit (Z 0 = 2). Each molecule consists of a 2-hydroxy Schiff base moiety linked through a spacer to a 2-aminobenzothiazole moiety. This spacer is both planar [r.m.s. deviations of fitted atoms of 0.004 (3) and 0.007 (3) Å , respectively for molecules A and B] and very close to coplanar with both the Schiff base and 2-aminobenzothiazole end moieties [making dihedral angles of 2.6 (9) and 4.0 (3) , respectively, in molecule A and 3.3 (8) and 3.9 (7) in molecule B]. The molecules themselves are very close to planar, as is shown by the dihedral angles of 4.0 (3) and 6.3 (2) between the two end groups for molecules A and B, respectively. Each molecule contains an intramolecular hydrogen bond between the OH group and imine N atom, forming a six-membered ring.

Supramolecular features
In addition to the intramolecular hydrogen bond mentioned above, the molecules are linked by a pair of C-HÁ Á ÁO hydrogen bonds (Table 1), forming dimers with an R 2 2 (20) ring motif, as shown in Fig. 1. These dimers are further linked into sheets in the ab plane by weak intermolecular C-HÁ Á ÁN interactions involving C15 and N2B, as shown in Fig. 2.

Synthesis and crystallization
A mixture of 0.505 g (4.10 mmol) salicylaldehyde and 0.746 g (4.10 mmol) 2-amino-6-methoxybenzothiozole was dissolved in 2 ml of acetonitrile in a vial. The mixture was reacted in a Biotage initiator eight mono mode microwave at 423 K for 2 min and then allowed to cool for 15 min. The resulting product was recrystallized from acetonitrile, filtered and then  Table 1 Hydrogen-bond geometry (Å , ). Symmetry code: (i) Àx þ 3 2 ; y À 3 2 ; z À 1 2 .

Figure 1
Molecular diagram for molecules A and B of the title compound, showing the atom labeling. Displacement parameters are drawn at the 30% probability level. The diagram shows the two molecules (A and B) linked into dimers by R 2 2 (20) C-HÁ Á ÁO hydrogen bonds (dashed lines; see Table 1 for details).