3-Anilino-5,5-dimethylcyclohex-2-enone

In the title molecule, C14H17NO, the 5,5-dimethylcyclohex-2-enone moiety is attached to an aniline group, the dihedral angle subtended [54.43 (3)°] indicating a significant twist. The hexaneone ring has a half-chair conformation with the C atom bearing two methyl groups lying 0.6384 (8) Å above the plane of the five remaining atoms (r.m.s. deviation = 0.0107 Å). The crystal packing can be described as alternating layers parallel to (-101), which are consolidated by N—H⋯O hydrogen bonds and C—H⋯π interactions.

In the title molecule, C 14 H 17 NO, the 5,5-dimethylcyclohex-2enone moiety is attached to an aniline group, the dihedral angle subtended [54.43 (3) ] indicating a significant twist. The hexaneone ring has a half-chair conformation with the C atom bearing two methyl groups lying 0.6384 (8) Å above the plane of the five remaining atoms (r.m.s. deviation = 0.0107 Å ). The crystal packing can be described as alternating layers parallel to (101), which are consolidated by N-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions.
Thanks are due to MESRS (Ministé re de l'Enseignement Supé rieur et de la Recherche Scientifique -Algeria) for financial support. The reaction of primary amines with ketones leads to imines; however, secondary amines give enamines. The preparation of enamines takes place when an aldehyde or ketone containing an α hydrogen is treated with a secondary amine. When enamines are treated with alkyl halides, an alkylation occurs to give an iminium salt via an electron transfer from the electron pair on nitrogen, through the C=C to the electrophilic carbon of the alkyl halide (Adams, 2000). In fact, an enamine behaves as a "nitrogen enolate" and generally react as carbon nucleophiles (Kempf et al., 2003). The use of enamine derivatives as intermediates in organic synthesis has been extensively investigated and they proved to be versatile precursors in the synthesis of a large variety of compounds of pharmaceutical interest (Tadesse et al., 1999;Park et al., 1998;Thummel & Jahng 1985;Palko et al., 2008). Inspired by the works of Assy 1996 and also as an extension of our ongoing research on the preparation and the reactivity of imidazole derivatives (Zama et al., 2013a;Zama et al., 2013b;Chelghoum et al., 2011;Bahnous et al., 2012), we describe herein the single-crystal X-ray structure of the enamine 5,5-dimethyl-3-(phenylamino)cyclohex-2-enone (I). This latter has been recovered from our attempt to coupling the dihydropyridine entity with imidazole unit using a "One Pot reaction" strategy implicating aniline, 5,5-dimethyl-1,3cyclohexandione and N-methylimidazolmethylenemalononitrile. The molecular geometry and the atom-numbering scheme of (I) are shown in Fig. 1. The asymmetric unit of (I) consists of the 5,5-dimethyl-cyclohex-2-enone moiety and its attached phenylamino group. The crystal packing can be described as alternating layers parallel to the (-101) (Fig. 2). It is stabilized by N-H···O hydrogen bond (Fig.3) and C-H···π interactions (Table. 1). These interaction bonds link the molecules within the layers and also link the layers together, reinforcing the cohesion of the structure.

Experimental
5,5-dimethyl-3-(phenylamino)cyclohex-2-enone (I) has been obtained from the reaction of aniline and 5,5-dimethyl-1,3cyclohexandione. In a typical reaction, 1 mmol of 5,5-dimethylcyclohex-1,3-dione, and 1 mmol aniline, in ethanol were placed in a 10 ml round-bottomed flask fitted with a condenser and a magnetic stirrer bar. The reaction mixture was stirred at reflux for 24 h, then 1 mmol of N-methylimidazolmethylenemalononitrile was added to this solution and the reaction mixture was heated for an additional 24 h. The solvent was distilled off and flash chromatographic purification furnished the 5,5-dimethyl-3-(phenylamino)cyclohex-2-enone I and the recovered N-methylimidazolmethylenemalononitrile. Suitable crystals for X-ray experiments of I were obtained by slow evaporation from an ethanol/CH2Cl2 solution at room temperature.

Refinement
Approximate positions for all the H atoms were first obtained from the difference electron density map. However, the H atoms were situated into idealized positions and the H-atoms have been refined within the riding atom approximation. -H = 0.86 Å; The idealized methyl group was allowed to rotate about the C-C bond during the refinement by application of the command AFIX 137 in SHELXL97 (Sheldrick, 2008). U iso (H methyl ) = 1.5U eq (C methyl ) or U iso (H aryl , methylene , amine ) = 1.2 U eq (C aryl , methylene or N).

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.