7H-[1,2]Benzothiazolo[3,2-b]quinazoline 5,5-dioxide

In the title compound, C14H10N2O2S, the benzothiazole and quinazoline ring systems are essentially planar with maximum deviations of 0.0127 (16) and 0.1588 (15) Å, respectively, and make a dihedral angleof 3.02 (5)°, which shows that the entire molecule is almost planar. The O atoms deviate from the benzothiazole ring system by 1.2231 (14) and −1.1989 (15) Å. The crystal packing features non–classical C—H⋯O hydrogen bonds and is further consolidated by π–π interactions [centroid–centroid distances = 3.7568 (8) and 3.8848 (9) Å].


Related literature
For the uses and biological importance of benzothiazole and quinazoline derivatives, see: Schwartz et al. (1992); Wolfe et al.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Saccharin belongs to a class of cyclic sulfonamides and this is used as an artificial sweetener for a longtime. The benzothiazole and quinazoline derivatives form an important classes of fused heterocyclic compounds with a wide range of biological activities such as antimicrobial (Schwartz et al., 1992), anticancer (Wolfe et al., 1990), antiinflammatory (Tereshima et al., 1995). As a part of our studies in this area, the molecular and crystal structures of the title compound have been determined and the results are presented here.
The title compound comprises a benzothiazole ring fused with quinazoline ring. X-ray analysis confirms the molecular structure and atom connectivity as illustrated in Fig. 1. The benzothiazole ring system is essentially planar with a maximum deviation of -0.0127 (16)Å for the C7 atom. The quinazoline ring system is also essentially planar with the maximum deviation of -0.1588 (15)Å for the N1 atom. The dihedral angle between the benzothiazole and quinazoline ring systems are almost coplanar with a dihedral angle of 3.02 (5)° between them.

Experimental
A solution of Saccharin (0.91 g, 5 mmol) and o-amino benzyl alcohol (0.61 g, 5 mmol) in DMF (10 ml) was irradiated with microwaves in a 800 W domestic microwave oven for 2 minutes. The reaction solution was cooled and poured over crushed ice (200 g). The precipitated product was filtered and desiccated over anhydrous CaCl 2 . The resulting filetered product was subjected to crystallization by slow evaporation of the solvent resulting in single crystals suitable for XRD studies.

Refinement
The positions of the hydrogen atoms were localized from the difference electron density maps and the distances were geometrically constrained. The H atoms bound to the C atoms, with d(C-H) = 0.93Å and U iso (H) = 1.2U eq (C) for aromatic, d(C-H) = 0.97Å and U iso (H) = 1.2U eq (C) for methylene.   Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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.