4-[(2,5-Dimethyl-1,3-thiazol-4-yl)methyl]-4-hydroxy-2-methylisoquinoline-1,3(2H,4H)-dione

In the title isoquinolinedione compound, C16H16N2O3S, the piperidine ring in the tetrahydroisoquinoline ring system adopts a half-boat conformation. The essentially planar thiazole ring [maximum deviation = 0.007 (2) Å] makes a dihedral angle of 34.49 (7)° with the mean plane through the tetrahydroisoquinoline ring system. In the crystal structure, two neighbouring molecules are linked via pairs of O—H⋯N and C—H⋯O hydrogen bonds into inversion-related dimers incorporating R 2 2(9) hydrogen-bond ring motifs. These dimers are further linked by weak intermolecular C—H⋯π interactions.

In the title isoquinolinedione compound, C 16 H 16 N 2 O 3 S, the piperidine ring in the tetrahydroisoquinoline ring system adopts a half-boat conformation. The essentially planar thiazole ring [maximum deviation = 0.007 (2) Å ] makes a dihedral angle of 34.49 (7) with the mean plane through the tetrahydroisoquinoline ring system. In the crystal structure, two neighbouring molecules are linked via pairs of O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds into inversion-related dimers incorporating R 2 2 (9) hydrogen-bond ring motifs. These dimers are further linked by weak intermolecular C-HÁ Á Á interactions.

[Cg1 and Cg2
are the centroids of the C3-C8 benzene ring and the thiazol ring, respectively].

Refinement
All the H atoms were located from difference Fourier map [range of C-H = 0.93 (3) -0.98 (3) Å] and allowed to refine freely. Fig. 1. The asymmetric unit of the title compound, showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% 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.