(Z)-Ethyl 2,4-diphenyl-3-(propylamino)but-2-enoate

The title compound, C21H25NO2, adopts a Z conformation about the C=C double bond. The molecular structure is stabilized by an intramolecular N—H⋯O hydrogen bond and the dihedral angle between the aromatic ring planes is 76.04 (12)°. The atoms of the ethyl substituent are disordered over two sets of sites in a 0.60 (2):0.40 (2) ratio.

The title compound, C 21 H 25 NO 2 , adopts a Z conformation about the C C double bond. The molecular structure is stabilized by an intramolecular N-HÁ Á ÁO hydrogen bond and the dihedral angle between the aromatic ring planes is 76.04 (12) . The atoms of the ethyl substituent are disordered over two sets of sites in a 0.60 (2):0.40 (2) ratio.

Experimental
Enamine compounds have been considered to be potential antibacterial agents (Xue et al., 2007) and found important application in the synthesis of N-containint heterocylcles (Du et al., 2006). To further study the structure and activity relationship, we determine the crystal structure of the title compound, (I).

S2. Experimental
The title compound was prepared according to the method of the literature (Du, et al., 2006). Colourless blocks of (I) were grown from a mixture of ethyl actate and petroleum ether.

S3. Refinement
The non-N H atoms were positioned geometrically (C-H = 0.93-0.98 Å) and refined as riding with U iso (H) = 1.2U eq (CH and CH 2 ) or 1.5U eq (CH 3 ). The N-H distance was refined with the restraint of 0.90 (1) Å, and the C19-C20, C20-C21, C9-C10 and C9-C10′ with the restraint of 1.54 (1) Å. The ethyl radical of the ester moiety was found to be disordered, with the site occupancy ratio of 0.40 (2)  The molecular structure of (I) with 50% probability displacement ellipsoids. The dashed line indicates the intramolecular N-H···O hydrogen bond.

(Z)-Ethyl 2,4-diphenyl-3-(propylamino)but-2-enoate
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.24 e Å −3 Δρ min = −0.19 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.079 (13) 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 Occ. (