3-Isopropyl-1-{2-[(1-methyl-1H-tetrazol-5-yl)sulfanyl]acetyl}-2,6-diphenylpiperidin-4-one hemihydrate

In the title compound, C24H27N5O2S·0.5H2O, the piperidine ring adopts a distorted boat conformation. The phenyl rings subtend dihedral angles of 69.7 (1) and 88.7 (1)° with the best plane through the piperidine moiety. In the crystal, symmetry-related molecules are linked through a network of C—H⋯O and C—H⋯N interactions, the former connecting them into zigzag chains along the c-axis direction and the latter forming an R 2 2(4)motif. The dimer formation (C—H⋯N) and the repetition of symmetry-related molecules (C—H⋯O) along the b-axis direction stabilize the packing mode. The water molecule is located on a twofold rotation axis.

In the title compound, C 24 H 27 N 5 O 2 SÁ0.5H 2 O, the piperidine ring adopts a distorted boat conformation. The phenyl rings subtend dihedral angles of 69.7 (1) and 88.7 (1) with the best plane through the piperidine moiety. In the crystal, symmetryrelated molecules are linked through a network of C-HÁ Á ÁO and C-HÁ Á ÁN interactions, the former connecting them into zigzag chains along the c-axis direction and the latter forming an R 2 2 (4)motif. The dimer formation (C-HÁ Á ÁN) and the repetition of symmetry-related molecules (C-HÁ Á ÁO) along the b-axis direction stabilize the packing mode. The water molecule is located on a twofold rotation axis.

Comment
In a way to find piperidin-4-one based lead drug molecules for the antimicrobial therapy, various piperidin-4-ones were prepared by condensing N-chloroacetyl-2,6-diphenylpiperidin-4-one with 5-mercapto-(1-methyltetrazole) (Aridoss et al., 2009). 5-Mercapto-(1-methyl tetrazole) is the active part of a number of cephalosporanic drugs like Cefamandole, Cefoperazone, Cefmetazole sodium & Cefotetan and responsible for its activity. The present investigation was undertaken to establish the structure and conformation of the title compound by X-ray crystallographic methods.

Experimental
To anhydrous DMF(10 ml), N-Chloroacetyl-3-isopropyl-2,6-diphenylpiperidin-4-one (1 mole), 5-Mercapto-1-methyltetrazole(1 mole) followed by potassium carbonate (1.5 mole) was added and stirred for 1 hr at room temperature. The reaction mass was heated to 60°C and stirred and monitored using TLC. After completion of reaction, the reaction mass was quenched into water and the product was extracted with dichloromethane. The dichloromethane layer distilled completely and to the residue methanol was added and kept in overnight. The solid obtained was filtered and dried at 60° C under vacuum. Single crystals were obtained by re-crystallization using ethanol.

Refinement
H atoms were positioned geometrically (C-H = 0.93-0.98 Å) and allowed to ride on their parent atoms, with U iso (H) =1.5U eq (C) for methyl H atoms and 1.2U eq (C) for all other H atoms. The ADP value for the water molecules is rather high. Since the H atoms of the solvent water molecule could not be located, they were not included in the refinement.

Figure 1
The molecular structure of the title compound, showing the atomic numbering and displacement ellipsoids drawn at 30% probability level.

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C2 0.36794 (