Crystal structure of (E)-4-(acetoxyimino)-N-allyl-3-isopropyl-2,6-diphenylpiperidine-1-carbothioamide

The title compound, C26H31N3O2S, crystallizes with two molecules (A and B) in the asymmetric unit. In each case, the piperidine ring exists in a twist-boat conformation. The dihedral angle between the phenyl rings is 46.16 (12)° in molecule A and 44.95 (12)° in molecule B. In both molecules, the allyl side chain is disordered over two orientations in a 0.649 (9):0.351 (9) ratio for molecule A and 0.826 (10):0.174 (10) ratio for molecule B. In the crystal, neither molecule forms a hydrogen bond from its N—H group, presumably due to steric hindrance. A+A and B+B inversion dimers are formed, linked by pairs of weak C—H⋯O hydrogen bonds enclosing R 2 2(22) ring motifs.

The bond distances and bond angles in the two independent molecules (A and B) of the title compound, Fig. 1, agree well with those reported for closely related compounds (Park et al., 2012a,b In the crystal, the individual molecules form A-A and B-B inversion dimers with R 2 2 (22) ring motifs (Table 1 and

S2. Synthesis and crystallization
To a solution of 3-isopropyl-2,6-diphenylpiperidin-4-one O-acetyl oxime (0.5 g, 1.5 mmol) in dry DCM (5 ml), pyridine (1.5 eq) and allylisothiocyanate (0.17 g, 1.75 mmol) were added drop wise over 5 min to a 50 ml Erlenmeyer flask. The reaction mixture was subjected to ultrasound irradiation for 1 h at ambient temperature and the progress of the reaction was monitored by TLC. Upon completion of the reaction, the mixture was slowly poured into crushed ice giving the crude product as a precipitate. It was subjected to recrystallization from absolute ethanol giving the title compound in good yield (0.62 g, 76%), as colourless block-like crystals.

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in  The molecular structure of molecule A of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The molecular structure of molecule B of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 3
A partial view of the crystal packing of the title compound, with the C-H···O hydrogen bonds shown as dashed lines (see Table 1 for details). Other H atoms and the minor components of the allyl groups have been omitted for clarity.
(E)-4-(Acetoxyimino)-N-allyl-3-isopropyl-2,6-diphenylpiperidine-1-carbothioamide where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.19 e Å −3 Δρ min = −0.24 e Å −3 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 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 Occ. (