(1R,2S,5R)-(–)-Menthyl (S)-2-(methoxycarbonyl)benzenesulfinate

In the title chiral sulfinic acid ester, C18H26O4S, the cyclohexane ring of the menthyl fragment adopts a chair conformation. The molecular shape is defined by the dihedral angle of 47.87 (8)° between the mean planes of the cyclohexane and benzene rings. In the crystal, molecules related by the screw axis are connected into chains along [010] by weak Car—H⋯O=S contacts.

In the title chiral sulfinic acid ester, C 18 H 26 O 4 S, the cyclohexane ring of the menthyl fragment adopts a chair conformation. The molecular shape is defined by the dihedral angle of 47.87 (8) between the mean planes of the cyclohexane and benzene rings. In the crystal, molecules related by the screw axis are connected into chains along [010] by weak C ar -HÁ Á ÁO S contacts.
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PARST (Nardelli, 1995). As a result of the trigonal pyramidal stereochemistry which characterizes the sulfur atom in organic sulfinic acid esters and sulfoxides bearing two different substituents, these species are chiral. Chiral sulfoxides are key intermediates for asymmetric synthesis and can be obtained from the reaction of an organometallic reagent (e.g. a Grignard reagent) with a diastereomerically pure sulfinate ester of menthol (Drabowicz et al., 1982). On the other hand, menthyl sulfinates can be prepared by reaction of menthol (Oertling et al., 2007) either with sodium sulfinates (Solladié et al., 1987) or with a sulfonyl chloride in the presence of trimethylphosphite as in situ reducing agent (Klunder & Sharpless, 1987). We used the latter method to prepare the chiral sulfinic acid ester, (1R,2S,5R)-(-)-menthyl (S)-2-carbomethoxybenzenesulfinate, here reported. The overall molecular shape of the title compound depends on the dihedral angle formed between the mean plane defined by the ring atoms of the menthyl and of the phenyl groupings (132.13° (8)). Bond distances and angles about the sulfur atom, as well as the orientation of the isopropyl chain with respect to the menthyl ring are in keeping with those already reported for this molecular fragment (Heinemann et al., 2007;Mariz et al., 2010;Cherkaoui & Nicoud, 1995). In the crystal, molecules are connected via weak C ar -H···O contacts involving the double bonded oxygen atom of the sulfinate group as acceptor. The resulting molecular chain propagates along the b axis direction around the screw axis.

Experimental
For the synthesis of the title compound, see: Klunder & Sharpless (1987). Crystals of the title compound suitable for single-crystal X-ray diffraction analysis were obtained by slow evaporation from a diethyl ether solution of the sulfinate ester.

Refinement
All the H atoms were positioned with idealized geometry using a riding model and refined with U iso (H) 1.2 times U eq (C) (1.5 for methyl H atoms).

Computing details
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PARST (Nardelli, 1995).  Crystal structure of the title compound with labelling and displacement ellipsoids drawn at the 50% probability level. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.15 e Å −3 Δρ min = −0.22 e Å −3 Absolute structure: Flack (1983), 767 Friedel pairs Flack parameter: 0.038 (18) Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.