N-acetonylsaccharin.

IN THE TITLE COMPOUND [SYSTEMATIC NAME: 2-(2-oxoprop-yl)-1,2-benzothia-zol-3(2H)-one 1,1-dioxide], C(10)H(9)NO(4)S, the benzo-thia-zole unit is essentially planar [maximum deviation = 0.0490 (9) Å for the S atom] and the oxopropyl group is inclined at an angle 75.61 (8)° with respect to its mean plane. In the crystal, mol-ecules are held together by weak inter-molecular C-H⋯O non-classical hydrogen bonds, resulting in centrosymmetric dimeric units, forming 14-membered ring systems which may be described as R(2) (2)(14) ring motifs. Moreover, mol-ecules lying about inversion centers show π-π inter-actions, with centroid-centroid separations between the benzene rings of 3.676 (2) Å.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SI2191).  (Singh et al. 2007), analgesic (Vaccarino et al. 2007), human leucocyte elastase (HLE) inhibitors (Kapui et al. 2003). In continuation to our project to explore potentially biologically active derivatives of benzothiazines (Ahmad et al. 2008), we herein report the crystal structure of the title compound, (I), in this paper.

Structure Reports Online
The structure of the title compound is depicted in Figure 1. The benzothiazol moiety (C1-C7/N1/S1) is essentailly planar with maximum deviation observed for S1 (0.0490 (9) Å) and the oxopropyl group (C8/C9/C10/O4) forms an angle 75.61 (8)° with the mean-plane of the former. The molecular dimensions in (I) agree with the corresponding molecular dimensions reported for a closely related compound (Ahmad et al. 2008). In the crystal structure, the molecules of (I) are held together by rather weak intermolecular C-H···O type non-classical hydrogen bonds resulting in dimeric units about inversion centers, forming fourteen membered ring systems which may be described in terms of graph set notation (Bernstein et al. 1994) as R 2 2 (14) ring motif; details are given in Table 1 and Figure 2. The molecules lying about inversion centers show π-π interactions with the separation between the centroids of the benzene rings (C1-C6) which are related by the symmetry operation: 1-x, 1-y, 1-z, is 3.676 (2) Å (Spek, 2009); with perpendicular distance being 3.354 Å and the slippage of 1.504 Å.

Experimental
Sodium saccharin (73.2 mmoles, 15.0 g) and chloroacetone (87.8 mmole, 7.0 ml) were added in a round bottom flask containing 30 ml of anhydrous DMF. The mixture was stirred under inert atmosphere for one hour at 393 K. The contents of the flask were poured in ice cold water. Brownish ppts. formed were filtered and washed with excess of water. Crystals suitable for XRD were grown in chloroform. Yield: 15.2 g, 87%; m.p. 386-387 K.

Refinement
Though all the H atoms could be distinguished in the difference Fourier map the H-atoms were included at geometrically idealized positions and refined in riding-model approximation with the following constraints: C-H distances were set to 0.95-0.99 Å and U iso (H) = 1.2U eq (C). The final difference map was free of any chemically significant features. Fig. 1. ORTEP-3 (Farrugia, 1997) drawing of (I) with displacement ellipsoids plotted at 50% probability level.

Figures
supplementary materials sup-2  as those based on F, and R-factors based on ALL data will be even larger.