(R)-2-Methyl-5-[(R)-2,4,4,4-tetrachlorobutan-2-yl]cyclohex-2-enone

The title compound, C11H14Cl4O, was efficiently synthesized by atom-transfer radical addition between (R)-carvone and tetrachloromethane. In the molecule, both chiral centres are of the absolute configuration R. The cyclohex-2-enone ring has an envelope conformation with the chiral C atom displaced by 0.633 (2) Å from the mean plane through the other five C atoms [maximum deviation = 0.036 (2) Å]. In the crystal, molecules are linked via C—H⋯O interactions, leading to the formation of helical chains propagating along [100].

The title compound, C 11 H 14 Cl 4 O, was efficiently synthesized by atom-transfer radical addition between (R)-carvone and tetrachloromethane. In the molecule, both chiral centres are of the absolute configuration R. The cyclohex-2-enone ring has an envelope conformation with the chiral C atom displaced by 0.633 (2) Å from the mean plane through the other five C atoms [maximum deviation = 0.036 (2) Å ]. In the crystal, molecules are linked via C-HÁ Á ÁO interactions, leading to the formation of helical chains propagating along [100].
The Kharasch addition or atom transfer radical addition (ATRA) is a synthetically useful process for functionalizing organic compounds by means of halogen derivatives (Dragutan et al., 2007). They are applied in the synthesis of polyfunctional acyclic and heterocyclic compounds, such as β-aminoacids (Juaristi & Soloschonok, 2005) and alkaloids (Nagashima et al., 2003). As a part of our interest in the synthesis of optically actives polyhalogenated products from terpenes (Boualy et al., 2009;Ziyat et al., 2004;Ziyat et al., 2006;Boualy et al., 2011) we report herein on the synthesis and crystal structure of the title compound. It is a new polyhalogenated terpene from (R)-carvone, which could be a valuable precursor for the synthesis of new polyfunctional terpenic compounds.
In the crystal, C-H···O interactions (Table 1 and  The structure of the title molecule was also characterized by 1 H, 13 C NMR spectroscopy and by mass spectroscopy. 1 H NMR data of the isolated product indicated the presence of an olefinic proton at 6.77 p.p.m. corresponding to the group (C═CH), which indicated also the absence of the olefinic protons of the group (C═CH 2 ). In the 13 C NMR spectrum, the signal of the carbonyl group was observed at δ = 199 p.p.m., the olefinic carbons appeared at 144.5 and 135.5 p.p.m. and the quaternary carbon containing three chlorine atoms appeared at 98.4 p.p.m. The conservation of the carbonyl group was also confirmed by the IR absorption at 1720 cm -1 . The mass spectrum of the compound confirmed the proposed structure exhibiting a molecular ion peak at m/z 304 and the base peak at m/z 136, which originated from the monoterpene fragment.
The X-ray single-crystal analysis of the title compound clearly shows the absolute configuration at atoms C1 and C7 to be (R, R) (Fig.1)

Experimental
The synthesis of the title compound (Boualy et al., 2011) is illustrated in Fig. 3. A mixture of Fe(acac) 3 (4.87 mg, 0.0138 mmol), NEt 3 (4.485 mg, 0.044 mmol), (R)-Carvone (207.30 mg, 1.38 mmol) and CCl 4 (849.09 mg, 5.52 mmol), was stirred in 353 K in 5 mL of toluene for 6 h and then hydrolyzed by addition of 20 mL of water. The organic layer was separated and the aqueous layer was washed with 3 × 10 mL of dichloromethane. The combined organic extracts were dried over Na 2 SO 4 and concentred in a rotary evaporator at reduced pressure. Column chromatography (hexane / ethyl acetate: 5:1 v/v) of the residue on silica gel gave 285.76 mg (0.94 mmol, 68%) of the title compound as a colourless solid.