1′-Acetyl-3-phenyl-6-oxa-4-thia-2-azaspiro[bicyclo[3.2.0]hept-2-ene-7,3′-indolin]-2′-one

In the title indoline compound, C19H14N2O3S, the pyrrolidine ring adopts an envelope conformation with the four-connected (spiro) C atom as the flap [displacement = 0.148 (3) Å]. The mean plane formed through the indoline unit is inclined at dihedral angles of 89.92 (16) and 59.54 (12)° with the thiazole and phenyl rings, respectively; the dihedral angle between the latter rings is 9.55 (14)°. In the crystal, pairs of intermolecular C—H⋯O hydrogen bonds link neighbouring molecules into inversion dimers, producing R 2 2(6) hydrogen-bond ring motifs. Weak intermolecular C—H⋯π as well as π–π interactions [centroid–centroid distance = 3.4041 (15) Å] further consolidate the crystal structure.

In the title indoline compound, C 19 H 14 N 2 O 3 S, the pyrrolidine ring adopts an envelope conformation with the four-connected (spiro) C atom as the flap [displacement = 0.148 (3) Å ]. The mean plane formed through the indoline unit is inclined at dihedral angles of 89.92 (16) and 59.54 (12) with the thiazole and phenyl rings, respectively; the dihedral angle between the latter rings is 9.55 (14) . In the crystal, pairs of intermolecular C-HÁ Á ÁO hydrogen bonds link neighbouring molecules into inversion dimers, producing R 2 2 (6) hydrogen-bond ring motifs. Weak intermolecular C-HÁ Á Á as well asinteractions [centroid-centroid distance = 3.4041 (15) Å ] further consolidate the crystal structure.

Experimental
The title compound was one of the products from the photoreaction between N-acetylisatin and 2-phenylthiazole. The compound was purified by flash column chromatography with ethyl acetate/petroleum ether (1:4) as eluents. Colourless blocks of (I) were obtained from slow evaporation of an acetone and petroleum ether (1:6) solution. M.p. 442-444 K.

Refinement
All hydrogen atoms were placed in their calculated positions, with C-H = 0.93-0.98 Å, and refined using a riding model, with U iso (H) = 1.2 or 1.5U eq (C). The rotating group model was applied to the methyl group. Fig. 1. The asymmetric unit of (I) with displacement ellipsoids for non-hydrogen atoms are drawn at the 50 % probability level.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
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 > 2sigma(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.