SYNTHESIS OF FATTY ESTERS CONTAINING A THIOLSULFINATE GROUP

Peracid oxidation of methyl 2-thialaurate [CH3(CH2)9-S-COOCH3, 1] gave methyl (decylsulfinyl)formate [CH3(CH2)9-SO-COOCH3, 2]. Compound 2 reacted spontaneously with silica gel to give decyl decanethiolsulfinate [CH3(CH2)9-SO-S-(CH2)9CH3, 3] in 84% yield. Thin layer chromatography of carbomethoxy 4-carbomethoxybutyl sulfoxide [CH3OOC(CH2)4-SO-COOCH3, 5] on silica gel furnished 4-carbomethoxybutyl 4-carbomethoxybutanethiolsulfinate [CH3OOC(CH2)4-SO-S-(CH2)4COOCH3, 6, 63%]. When a mixture of compounds 2 and 5 was chromatographed on silica gel, a mixture of decyl 4-carbomethoxybutanethiolsulfinate [CH3(CH2)9-S-SO-(CH2)4COOCH3, 7] and 4-carbomethoxybutyl decanethiolsulfinate [CH3(CH2)9-SO-S-(CH2)4COOCH3, 8] was obtained in 20.2% yield in addition to compounds 3 (38%) and 6 (32%). Compound 7 was confirmed by coupling the sulfinyl chloride derivative of methyl 5-mercaptopentanoate with decanethiol. Compound 8 was prepared from the sulfinyl chloride derivative of decanethiol and methyl 5-mercaptopentanoate. The thiolsulfinate group gave a characteristic absorption peak at about 1080 cm-1 (S=O, str.) in the infrared spectrum. The chemical shifts of the protons of the methylene groups adjacent to the thiolsulfinate group appeared at delta 3.12 (t, J = 7.5 Hz). In the C-13-NMR analysis, the shifts of the methylene carbon atoms adjacent to the thiolsulfinate group appeared at approximately 32 (-SO-S-CH2-) and at 55 (-S-SO-CH2-) ppm.