(1R,5R)-2H-1,5-Benzodithiepin-3(4H)-one 1,5-Dioxide

Abstract

[183595-53-1] C9H8O3S2 (MW 228.29 InChI = 1S/C9H8O3S2/c10-7-5-13(11)8-3-1-2-4-9(8)14(12)6-7/h1-4H,5-6H2 InChIKey = ZKBLWRRLZIMWNI-UHFFFAOYSA-N (chiral auxiliary for asymmetric desymmetrization of cyclic meso-1,2-diols) Alternate Name: 2H-1,5-benzodithiepin-3(4H)-one, 1,5-dioxide, (1R-trans)-; (1R,5R)-1,5-benzodithiepan-3-one 1,5-dioxide. Physical Data: colorless prisms, mp 195.0–196.0°C (decomposes) (from hexane/EtOAc), [α]D25−100.3 (c 0.29, CHCl3). Solubility: soluble in MeOH, acetone, EtOAc, THF, CH2Cl2, and CHCl3. Form Supplied in: colorless powder; not commercially available. Analysis of Reagent Purity: 1H and 13C NMR; elemental analysis. Preparative Methods: the title reagent can be prepared from commercially available (1,2-benzenedithiol1 and 1,3-dichloroacetone. After condensation of these reagents in the presence of DMAP, the resulting 1,5-benzodithepan-3-one is enantioselectively oxidized to the (R)-monosulfoxide by modified Sharpless oxidation [cumene hydroperoxide, Ti(O-i-Pr)4] in the presence of (+)-diethyl tartrate as a chiral ligand.2, 3 Subsequent dry ozonation4 of the (R)-monosulfoxide affords (1R,5R)-bis-sulfoxide 1, having >98% optical purity. Alternative use of (−)-diethyl tartrate in the modified Sharpless oxidation makes possible convenient access to enantiomeric (1S,5S)-1.5, 6 Purification: purification is performed by column chromatography. Since unpurified (1R,5R)-bis-sulfoxide 1 is only slightly soluble in the eluent, the following procedure is convenient. The crude material is dissolved in EtOAc and mixed with silica gel (ca. 5 g silica gel per 1 g of crude reagent). After solvent evaporation, the silica gel residue containing 1 is added to the top of the column and eluted with hexane–EtOAc (2:1). Handling, Storage, and Precautions: the reagent can be stored for at least 1 month at room temperature without loss of its chemical and optical purities.