Organosulfur compounds. 30. Improved procedure for synthesis of chiral sulfoxides

Synthesis of 2-Fluoro Analogues of Frontalin

“…2-Fluorofrontalin (-)-(1R,2S,5R)-7 Both the C-2 epimers of enantiomeric (ϩ)-fluorofrontalin, (1S,2S,5S)-and (1S,2R,5S)-7, were obtained following an identical synthetic procedure starting from (Ϫ)-(1R)-menthyl-(S)-toluene-4-sulfinate as the chiral source of the synthesis. [8] The assignment of the stereochemistry was based on an X-ray analysis of (1S,2R,5S,R S )-5, one of the intermediates in the synthesis of (ϩ)-(1S,2R,5S)-7 frontalin.…”

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

“…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).…”

“…For the synthesis of the title compound, see: Klunder & Sharpless (1987) and of chiral sulfoxides, see: Drabowicz et al (1982); Solladié et al (1987). For applications of menthol in synthetic chemistry, see Oertling et al (2007).…”

Self-disproportionation of enantiomers (SDE) of chiral sulfur-containing compounds via achiral chromatography

“…Very recently this initial study of the SDE phenomenon for sulfoxides by gravity-driven column chromatography over achiral silica gel was performed in our group 39 by more detailed experiments with the use of methyl n-pentyl sulfoxide 11 (MPS 11) as the analyte. The samples needed of this sulfoxide, enriched in the R enantiomer, were prepared according to a literature modification 92 of the Andersen methodology 93 by a Grignard reaction between n-pentylmagnesium bromide and O-menthyl methanesulfinate 10, which in turn was produced as a pair of diastereomers by the reaction of methylsulfinyl chloride 9 and (−)-menthol (Scheme 8). We decided to use for our study MPS 11 having a relatively modest enantiomeric purity (34.62% ee enriched in the R enantiomer) in order to determine if it is indeed possible to obtain a sample with high optical purity, e.g.…”