(3E,5E)-1-Allyl-3,5-bis(4-methoxybenzylidene)piperidin-4-one

The piperidine ring in the title compound, C24H25NO3, adopts an envelope conformation with the N atom being the flap atom, and each C=C double bond exhibits an E conformation. In the crystal, C—H⋯O hydrogen bonds link the molecules, forming supramolecular layers that stack along the a axis.

The piperidine ring in the title compound, C 24 H 25 NO 3 , adopts an envelope conformation with the N atom being the flap atom, and each C C double bond exhibits an E conformation. In the crystal, C-HÁ Á ÁO hydrogen bonds link the molecules, forming supramolecular layers that stack along the a axis.

Suresh Comment
Piperidine ring systems are of immense interest in the pharmaceutical industry as they exhibit a wide range of biological activities (Guengerich et al., 1973;Puder et al., 2000). A number of alpha,beta-unsaturated ketones display cytotoxic and anti-cancer properties (Dimmock, Elias et al., 1999; besides being useful synthons for the construction of diverse structurally complex heterocycles. The biological importance of these heterocycles in conjunction with our research interests (Suresh et al., 2007), prompted us to synthesize and report the X-ray studies of the title compound.
In the title compound (Fig 1), the six-membered piperidone ring adopts a sofa conformation which is evidenced by the puckering parameters: q 2 = 0.5517 (16) Å, θ = 123.96 (5)°, φ = 178 (6)° (Cremer & Pople, 1975). Both olefinic double bonds have an E configuration, and the aryl rings are not coplanar with either the adjacent olefinic double bonds or the planar portion of the piperidone ring. The aryl rings are rotated to move atoms C5 and C15 from the plane of the other five atoms of the piperidone ring in the opposite direction of the displacement of atom N1. As the result the torsion angles C5-C6-C7-C8 and C10-C11-C13-C14 have values 31.9 (2) and -4.2 (2)° respectively. This lack of co-planarity is caused by non-bonded interactions between one of the ortho-H atoms in the aryl ring and the equatorial H atoms at the 2-and 6-positions of the piperidone ring (H5A/H9A or H9B and H15A/H10A or H10B). These steric repulsions are reduced by the expansion of the bond angle C6-C7-C8 and C11-C13-C14 which are 130.23 (19) and 130.67 (2)° respectively (otherwise 120°).
The C10-H10A···O3 hydrogen bond connect two molecules forming an inverse related dimers which are interlinked by C21-H21C···O2 intermolecular hydrogen bonds to form a supramolecular layer in the bc plane.

Experimental
A equimolar mixture of (3E,5E)-3,5-bis(4-methoxybenzylidene)piperidin-4-one (0.023 g), allyl chloride (0.100 g) and K 2 CO 3 (0.041 g) in acetone (30 ml) was stirred at room temperature for 30 minutes. After completion of the reaction as evident from TLC, the excess solvent was removed under vacuum and the crude product was extracted with ethyl acetate and recrystallized from the same to afford the title compound. M. pt: 270-272 K. Yield: 92%.

Refinement
H atoms were placed at calculated positions and allowed to ride on their carrier atoms with C-H = 0.93-0.97 Å, and with U iso = 1.2-1.5U eq (C).

Figure 1
The molecular structure of (I), showing 30% probability displacement ellipsoids and the atom-numbering scheme. 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.