N-[2-(N-Cyclohexylcarbamoyl)propan-2-yl]-N-(2-iodophenyl)prop-2-ynamide

In the title compound, C19H23IN2O2, the cyclohexane ring adopts a chair conformation, and the mean plane of the propiolamide unit is approximately perpendicular to the benzene ring [dihedral angle = 88.12 (13)°]. Weak intramolecular C—H⋯O hydrogen bonding is observed between the carbonyl group and the benzene ring. In the crystal, classical N—H⋯O hydrogen bonds and weak C—H⋯O interactions are present.

In the title compound, C 19 H 23 IN 2 O 2 , the cyclohexane ring adopts a chair conformation, and the mean plane of the propiolamide unit is approximately perpendicular to the benzene ring [dihedral angle = 88.12 (13) ]. Weak intramolecular C-HÁ Á ÁO hydrogen bonding is observed between the carbonyl group and the benzene ring. In the crystal, classical N-HÁ Á ÁO hydrogen bonds and weak C-HÁ Á ÁO interactions are present.
The iodophenyl group in the title compound is oriented orthogonal to the amid group, meaning that there is no conjugation between these two pi systems. The two amid groups themselves however are planar as expected, indicating a considerable amount of π-conjugation in the N-C=O units, thus partially double bond character and hindered rotation around the amide single bonds. The crystal lattice is stabilized by weak intermolecular N-H···O=C type hydrogen bonding with N1 acting as hydrogen donor and O6 as hydrogen acceptor, leading to one-dimenssional chains in crystallographic a direction. The N···O distance amounts to 3.015 (3) Å and the N-H···O angle to 163 (1)°. Intermolecular N-H···O and C-H···O hydrogen bond are effective in the stabilization of the crystal structure of the title compound (Table 1 & Fig. 2).

Experimental
The product was obtained via a four-component reaction of acetone, 2-iodo-aniline, propiolic acid, and cyclohexylisocyanide in methanol at room temperature. To a solution of acetone (58 mg, 1 mmole) in methanol (5 mL) 2-iodo-aniline (219 mg, 1 mmol) was added. The reaction mixture was stirred at room temperature for 1 h. Then propiolic acid (70 mg, 1 mmol) was added and stirring was continued for 15 min, followed by the addition of cyclohexylisocyanide (1 mmol, 123 mg). After stirring for 24 h at room temperature the reaction mixture was neutralized with 30 mL saturated aqueous NaHCO 3 solution and extracted with EtOAc (3 × 20 mL). The combined organic layers were dried with anhydrous magnesium sulfate and the solvent was evaporated. The residue was crystallized from acetonitrile.

Refinement
Imino H atom was located in a difference Fourier map and refined isotropically. Other H atoms were positioned geometrically with C-H = 0.95-1.00 Å and constrained to ride on their parent atoms, U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for the others.

Special details
Experimental. Hydrogen atom positions were calculated according to geometrical criteria except the amide hydrogen atom H1, which was refined isotropically. The thermal parameters of the hydrogen atoms were set to be 1.2 times the U eq of the preceding carbon atom, 1.5 for the methyl groups. The conformation of the methyl hydrogen atoms was allowed to refine. The symmetry of the crystal is chiral, albeit a racemic twinning parameter was introduced and refined to 24% racemic twinning.
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 mat-