2-[(1S,3S)-3-Acetyl-2,2-dimethylcyclobutyl]-N-(m-tolyl)acetamide

The title compound, C17H23NO2, contains two chiral centres and was synthesized from 2-(3-acetyl-2,2-dimethylcyclobutyl)acetic acid and m-toluidine. The cyclobutane ring is not flat but flexed as though folded from the dimethyl-substituted C atom to the unsubstituted C atom, with a dihedral angle of 25.9°. The crystal structure is stabilized by N—H⋯O and C—H⋯O hydrogen-bonding interactions.

The title compound, C 17 H 23 NO 2 , contains two chiral centres and was synthesized from 2-(3-acetyl-2,2-dimethylcyclobutyl)acetic acid and m-toluidine. The cyclobutane ring is not flat but flexed as though folded from the dimethylsubstituted C atom to the unsubstituted C atom, with a dihedral angle of 25.9 . The crystal structure is stabilized by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen-bonding interactions.

S1. Comment
Terpenes are convenient chiral precursors due to their availability and low cost, and among them, a-pinene (both enantiomers) and verbenone are prominent. For instance, pinene has been used as starting material for the production of some compounds of industrial interest (Mitra & Khanra, 1977). Chiral cyclobutane compound, pinonic acid, can be synthesized from a-pinene. Many derivatives of pinonic acid have interesting biological properties. So we synthesized several derivatives of pinonic acid. In our previous paper we have reported the crystal structure of 2-[(1S,3S)-3acetyl-2,2-dimethylcyclobutyl]-N-(2,6-difluorophenyl) acetamide (Yin et al., 2007). Now we synthesized the title compound (I) and report here its crystal structure.
The molecular structure of (I) is shown in Fig. 1. A l l bond lengths and angles are normal. The crystal structure is stabilized by N-H···O and C-H···O hydrogen bonding interactions (Table 1).

S2. Experimental
The title compound was synthesized from m-toluidine and 2-(3-acetyl-2,2-dimethylcyclobutyl) acetyl chloride at room temperature. The acetyl chloride was obtained using 2-(3-acetyl-2,2-dimethylcyclobutyl)acetic acid (pinonic acid), thionyl chloride as raw materials and dichloromethane as solvent. Pinonic acid (27 mmol) and thionyl chloride (32 mmol) were dissolved in dichloromethane (50 ml). The resulting mixture was refluxed for 8 h. After refluxing the solvent was distilled away under vacuum and the remainder was 2-(3-acetyl-2,2-dimethylcyclobutyl)acetyl chloride. The acetyl chloride reacted with m-toluidine (27 mmol) for 24 h using dichloromethane as solvent. After the reaction was complete the solvent was distilled away and the crude title compound was gained. The pure compound was obtained by crystallizing from a mixture of ethanol (40 ml) and water (40 ml). Crystals of the title compound suitable for X-ray diffraction were obtained by slow evaporation of an ethanol solution.

S3. Refinement
All H atoms were placed geometrically, with the C-H distances in the range 0.93-0.98 Å and N-H = 0.86 Å, and included in the refinement in riding motion approximation with U iso (H) = 1.2 or 1.5U eq (H) of the carrier atom.  A view of the molecular structure of (I), showing displacement ellipsoids at the 50% probability level.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq N 0.7095 (2)