(Z)-Ethyl 3-(2,6-diisopropylanilino)but-2-enoate

The title compound, C18H27NO2, crystallizes as the enamine form with Z geometry. The β-enaminoester fragment forms a dihedral angle of 87.5 (1)° with the isopropylphenyl frame. The structure exhibits an intramolecular N—H⋯O hydrogen bond. In addition, in the crystal, molecules are linked by a centrosymmetric intermolecular N—H⋯O hydrogen bond.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: GW2075).
important precursors in organic synthesis, these are particularly useful as they can be further transformed to key intermediates of several pharmaceutical products (Michael et al., 1999). They have been utilized for the preparation of different important aminoacids (Palmieri et al., 1996), peptides and alkaloids (David et al., 1999). In continuation of our work in enaminoesters synthesis (Amézquita-Valencia, et al. 2009), we describe the structure of title compound (I) obtained using a Mexican bentonitic clay as catalist.

Experimental
Compound (I) was obtained following the procedure described in Amézquita-Valencia, et al. 2009. The product recrystallized from methanol. Yield: 92%, M.p. 326.3°R efinement H atom on amine group was found in Fourier map and refined with U iso (H) = 1.2 UeqC(sp2). H on C atoms were placed in geometrically idealized positions [0.93 Å(CH) 0.96 Å(CH arom) and 0.97 Å (CH3)] tied to the parent atom with U iso (H) = 1.2 UeqC(sp2) and 1.5 UeqC(sp3) and refined using the riding model. Fig. 1. The Molecular structure of (I) with the atom numbering scheme. Displacement ellipsoids are drawn at the 40% probability level. H atoms bonded to C omitted. The intramolecular hydrogen bond is shown as a dashed line. (Z)-Ethyl 3-(2,6-diisopropylanilino)but-2-enoate

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 Rfactors(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.