Study on the synthetic reactions of α-thiosilane derivatives

Abstract

Several α-thiosilane deriveatives were synthesized by the reaction of chloro(phenylthio)methyltrimethyl silane with nucleophiles. Nucleophiles employed were Grignard reagents, organoalanes, alcohols, and thiols to give α-alkylated, alkenylated, or alkynylated thiosilanes, α-silyl monothioacetal, and α-silyl dithioacetal, respectively. Chemoselectivity in the Lewis acid promoted reactions of various monothioacetals was investigated through the reaction with several nucleophiles such as phosphites, arenes and alk-1-enes. Monothioacetal of benzaldehyde showed chemoselective phosphorylation by the alternation of the Lewis acid employed, whereas monothioacetal of n-heptanal did not. α-Silyl monothioacetal worked only as α-phenylthiosilylmethyl carbocation equivalent in the Lewis acid mediated reaction with phosphites, arenes, and alk-1-enes. α Phosphoryl monothioacetal showed the same cleavage pattern in the Lewis acid mediated reaction with arenes. The preparation of several functionalized vinyl sulfides was performed. α -Silyl vinyl sulfides was obtained by the reaction of α-thiosilylalkanes with N-chlorosuccinimide via the intermediary α-chloro sulfides without the addition of external base or acid. Employment of two equivalents of NCS gave 1, 2-dichloro-2-phenylthio-2-silylalkanes, which underwent a facile β-elimination of HCL by the treatment with silica to give the corresponding β chloro-α silyl vinyl sulfides. This 1, 2-dichlorinated adducts could also be converted into α-chloro vinyl sulfides by the treatment with potassium fluoride dihydrate in DMSO. α-Cyano vinyl sulfides were prepared using the Peterson olefination method. The Peterson reagent, prepared by the silylation of methylthioacetonitrile using TMSOTf, could be extended to enolizable carbonyl compounds.