2-(2-Oxo-2-phenylethyl)-1,2-benzisothiazol-3(2H)-one 1,1-dioxide

In the title compound, C15H11NO4S, the benzothiazole unit is essentially planar [maximum deviation = 0.0644 (14) Å for the N atom] and forms a dihedral angle 54.43 (6)° with the phenyl ring. In the crystal structure, weak bifurcated C—H⋯O hydrogen bonds involving the carbonyl O atoms as acceptors result in R 2 2(7) ring motifs.


Related literature
In continuation of our research on the synthesis of potential biologically active derivatives of benzothiazines (Ahmad et al., 2008;Ahmad et al., 2009), we herein report the crystal structure of the title compound, N-phenacylsaccharin, (I).
The structure of (I) contains discrete molecules separated by normal van der Waals distances (Fig. 1). The benzothiazole moiety (S1/N1/C1-C7) is essentially planar (maximum deviation = 0.0644 (14) Å for N1-atom) and lies at an angle 54.43 (6) ° with respect to the phenyl ring (C10-C15). The structure is devoid of any classical hydrogen bonds. However, non-classical hydrogen bonding interactions of the type C-H···O are present in the crystal structure involving O1 and Hatoms bonded to C8 and C15 resulting in a seven membered ring in R 2 2 (7) motif (Bernstein et al., 1995) ( Fig. 2 and Table 1).

Experimental
Phenacyl bromide (4.85 g, 0.024 mol) was slowly added to a suspension of sodium saccharine (5 g, 0.024 mol) in dimethylformamide (15 ml) and the mixture was stirred at 383 K for 3 hours under anhydrous conditions. On completion of reaction (as indicated by tlc), the mixture was poured on crushed ice and the precipitates formed were filtered and washed with excess of distilled water and cold ethanol respectively. The crystals of N-phenacylsaccharin suitable for XRD were grown from a solution of chloroform-methanol (3:1).

Refinement
All the H-atoms were located from the difference Fourier maps and were included in the refinements at geometrically idealized positions with C-H distances = 0.95 and 0.99 Å for aryl and methylene H-atoms, respectively, and U iso = 1.2 times U eq of the C-atoms to which they were bonded. The final difference map was free of chemically significant features.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 Rfactors(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.