(R,E)-3-(4-Chlorophenyl)-1-phenylallyl 4-nitrobenzoate

The title compound, C22H16ClNO4, adopts a conformation in which the phenyl ring plane forms similar dihedral angles with the nitrobenzoate C6 ring [76.97 (8)°] and the chlorophenyl group [76.95 (8)°]; the dihedral angle between the chlorophenyl and nitrobenzoate rings is 66.43 (8)°. In the crystal, π–π stacking is observed between the latter two planes, with a dihedral angle of 1.79 (8)° and a centroid–centroid distance of 3.735 (1) Å. In addition, molecules are linked along [100] by weak C—H⋯O contacts.

The asymmetric unit contains one molecule of the title compound (I) which is shown in Figure 1. The plane defined by C4, C7, C8 and C9 (contains the allyl group) is not exactly coplanar with the adjacent chlorophenyl moiety (dihedral angle 9.71 (17)°). A deviation of coplanarity of a similar magnitude (6.5 (3)°) is observed in a related structure with a phenyl group as adjacent moiety [Cao et al. 2011)], while a less deviation (dihedral angle 1.7 (6)°) is observed in a related structure with a p-toluyl group as adjacent moiety [Wang et al. (2009)]. A slight deviation from coplanarity is observed in the nitrobenzoate group as well. The plane of the nitro group is almost coplanar with the phenyl ring enclosing a dihedral angle of 0.9 (2)°. However, the plane of the CO 2 group forms a dihedral angle of 10.16 (19)° with the phenyl ring.
The packing of (I) is shown in Figure 2. π-stacking is established between the chlorophenyl and nitrobenzoate moieties.

Experimental
A four step synthesis was used to obtain the title compound (I).

Refinement
C-bound H atoms were positioned geometrically in ideal distances (0.95 Å for aromatic H and 1.00 Å for aliphatic H) and treated as riding on their parent atoms [U iso (H) = 1.2U eq (C)].

Figure 1
The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level) for non-H atoms.    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 > 2σ(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 Cl1