[H-].[K+].O1[CH2:7][CH2:6][CH2:5][CH2:4]1.[CH3:8][S:9][CH2:10][S:11](=[O:13])[CH3:12].BrCCCCBr>C(Cl)Cl>[CH3:8][S:9][C:10]1([S:11](=[O:13])[CH3:12])[CH2:7][CH2:6][CH2:5][CH2:4]1Potassium hydride (940 mg) was suspended in 15 ml. of tetrahydrofuran, and with ice cooling, 1.320g of formaldehyde dimethyl mercaptal S-oxide was added. With ice-cooling, the mixture was stirred for 40 minutes, and then 2.410 g of 1.4-dibromobutane was added. The mixture was stirred for 1 hour with ice cooling, and then for 19 hours at room temperature. Methylene chloride (70ml) was added, and the insoluble matter was separated by filtration. The filtrate was concentrated at reduced pressure, and the residue was separated by column chromatography (silica gel, eluted with CH2Cl2, 25% AcOEt-CH2Cl2, AcOEt, and MeOH) to afford 1.509 g of cyclopentanone dimethyl mercaptal S-oxide as a colorless oily substance. Furthermore, 208 mg of formaldehyde dimethyl mercaptal S-oxide was obtained from the MeOH fraction. The yield was 80%. The physical properties were as follows:
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