Crystal structure of ethyl (2Z)-2-cyano-3-[(3-methyl-1-phenyl-1H-pyrazol-5-yl)amino]prop-2-enoate

The title compound, C16H16N4O2, crystallizes with two molecules in the asymmetric unit, one of which shows disorder of the acetate group over two sets of sites in a 0.799 (2):0.201 (2) ratio. The phenyl group has a similar but opposite sense of twist relative to the pyrazole ring in the two molecules, as indicated by the syn N—N—Car—Car (ar = aromatic) torsion angles of 39.7 (2) and −36.9 (2)°. Each molecule features an intramolecular N—H⋯O hydrogen bond, which closes an S(6) ring. In the crystal, C—H⋯O and C—H⋯N interactions direct the packing into a layered structure parallel to (110).


S1. Comment
Acrylate compounds have been receiving significant attention in the fields of materials and pharmaceutical sciences due to their physical and biological properties (Wang et al., 2003;Dillingham et al., 1983). For example, cyanoacrylates are widely used as inhibitors for the photosystem II (PSII) which inhibits the growth of weeds by disrupting photosynthetic electron transport (Liu et al., 1999). Among these cyanoacrylates, 3-(4-chlorobenzyl)amino-2-cyano-3-isobutylacrylate exhibits the highest inhibitory activity of the Hill reaction (Wang et al., 2003). Moreover, 3-aminoacrylates can also be hydrogenated into β-amino acid derivatives which have extensive application in life sciences as components of biologically active peptides and small-molecule pharmaceuticals (Hsiao et al., 2004). In addition, acrylates also represent an important class of organic compounds which are employed as important intermediates in organic synthesis due to the chemical versatility of the acrylate moiety and continue to attract considerable attention of chemists (Kang & Fang, 2004;Qiu et al., 2004). Based on such findings and following our on-going study of acrylate base pyrazoles we herein report the synthesis and crystal structure study of the title compound.
The title molecule crystallizes with two independent molecules in the asymmetric unit (Fig. 1). These differ primarily in the orientation of the phenyl ring with respect to the mean plane of the pyrazole ring. Thus the dihedral angle between the C1-C6 phenyl ring and the pyrazole ring built on N1 is 43.90 (6)° while that in the other molecule is 37.38 (6)°. The two molecules are nearly parallel as seen from the angle between the mean planes of the pyrazole cores of 2.5 (1)°. The molecular conformations are partly determined by intramolecular N3-H3a···O1 and N7-H7a···O3 hydrogen bonds (Table 2 and Fig. 1) while C-H···O and C-H···N interactions direct the packing into a layer structure ( Fig. 3 and Table   2).

S3. Refinement
H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.98 Å) while those attached to nitrogen were placed in locations derived from a difference map and their parameters adjusted to give N-H = 0.91 Å. All were included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms. The supporting information sup-2 major portion of the side chain in molecule 1 is disordered over two reasonably resolved sites in a 4:1 ratio. The two components of the disorder were refined subject to restraints that their geometries be comparable to one another and to that of the corresponding ordered portion of molecule 2.

Figure 1
Perspective view of the asymmetric unit with 50% probability ellipsoids and intramolecular N-H···O hydrogen bonds shown as dotted lines. Only the major portion of the disorder in molecule 1 is shown.

Figure 2
Packing viewed towards the [110] plane with intramolecular N-H···O hydrogen bonds shown as blue dotted lines and intermolecular C-H···O and C-H···N interactions as red and black dotted lines, respectively.