Absolute configuration of (1S,2S)-3-methyl-2-phenyl-2,3-dihydrothiazolo[2,3-b]quinazolin-5-one

The absolute structure of the molecule in the crystal of the title compound, C17H14N2OS, was determined by the refinement of the Flack parameter to 0.0 (2) based on 1011 Friedel pairs. The quinazoline ring is essentially planar, with a maximum deviation of 0.037 (2) Å. The thiazole ring is distorted from planarity [maximum deviation = 0.168 (2) Å] and adopts a slightly twisted envelope conformation, with the C atom as the flap atom. The central thiazole ring makes dihedral angles of 7.01 (8) and 76.80 (10)° with the quinazoline and phenyl rings, respectively. The corresponding angle between the quinazoline and phenyl rings is 3.74 (9)°. In the crystal, there are no classical hydrogen bonds but stabilization is provided by weak C—H⋯π interactions, involving the centroids of the phenyl rings.

The absolute structure of the molecule in the crystal of the title compound, C 17 H 14 N 2 OS, was determined by the refinement of the Flack parameter to 0.0 (2) based on 1011 Friedel pairs. The quinazoline ring is essentially planar, with a maximum deviation of 0.037 (2) Å . The thiazole ring is distorted from planarity [maximum deviation = 0.168 (2) Å ] and adopts a slightly twisted envelope conformation, with the C atom as the flap atom. The central thiazole ring makes dihedral angles of 7.01 (8) and 76.80 (10) with the quinazoline and phenyl rings, respectively. The corresponding angle between the quinazoline and phenyl rings is 3.74 (9) . In the crystal, there are no classical hydrogen bonds but stabilization is provided by weak C-HÁ Á Á interactions, involving the centroids of the phenyl rings.
The absolute configuration of the molecule were determined by the refinement of the Flack parameter to 0.0 (2). There are two chiral centres in the molecule. From the structure presented, these centers exhibit the following chiralities: C1 = S and C2 = S.
In the crystal structure (Fig. 2), there are no classical hydrogen bonds but stabilization is provided by weak C-H···π interactions (Table 1) involving the centroids of the (C4-C9) and (C11-C16) phenyl rings.

Experimental
A mixture of 2-isothiocyanatobenzoate (1.93 g, 0.01 mole) and 2-amino-1-phenylpropan-1-ol (1.51 g, 0.01 mole) in dry dimethylformamide (30 ml) containing a catalytic amount of triethylamine was refluxed for 6 h. The solid obtained was recrystallized from ethanol to give the title thiazoloquinazline derivative compound. Single crystals suitable for X-ray structural analysis were obtained by slow evaporation from ethanol at room temperature.

Figure 1
The asymmetric unit of the title compound, showing 30% probability displacement ellipsoids.

(1S,2S)-3-methyl-2-phenyl-2,3-dihydrothiazolo[2,3-b]quinazolin-5-one
Friedel pairs Flack parameter: 0.00 (2) 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 > 2σ(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.