“…In the case of Me,SiR where R = -CH,M!Ie2, -CH,CH,NH,, -CH,CH,CO,H, -CH,CH2COMe, etc., one mole of methane is evolved per mole of tetraorganosilanes [6]: hle,SiR + H,SO, ___ + I\/le,Si(HSO,)R + CH,.…”
“…In the case of Me,SiR where R = -CH,M!Ie2, -CH,CH,NH,, -CH,CH,CO,H, -CH,CH2COMe, etc., one mole of methane is evolved per mole of tetraorganosilanes [6]: hle,SiR + H,SO, ___ + I\/le,Si(HSO,)R + CH,.…”
“…2]. In 1953, Sommer and co‐workers reported a concentrated sulfuric acid‐aided synthesis of aliphatic organosiloxanes through the cleavage of one methyl group from the trimethylsilyl moiety [6a] . Kinetic studies confirmed a pseudo‐first order character of the reaction, involving an “electrophilic attack” on the carbon center followed by the formation of methane and a (at least formally) silylium‐ion intermediate in the rate‐determining step [6b] .…”
For a long time, the Me3Si group has been ostracized from the family of aryl‐ and heteroatom‐substituted congeners for the difficulties associated with its further chemoselective manipulation into another synthetically useful functional group. A hypervalent iodine reagent has now been shown to do exactly that by electrophilic demethylation. Coupled with the Tamao–Fleming oxidation, the Me3Si group becomes a placeholder for a hydroxy group.
“…2]. Sommer und Mitarbeiter berichteten 1953 von einer mit konzentrierter Schwefelsäure ermöglichten Herstellung aliphatischer Organosiloxane durch die Abspaltung einer Methylgruppe von der Trimethylsilyleinheit [6a] . Kinetische Untersuchungen sprachen für eine Reaktion pseudo‐1.…”
Die Me3Si‐Gruppe wird schon lange aus der Familie ihrer aryl‐ und heteroatomsubstituierten Artgenossen ausgegrenzt, da sie sich nur schwer chemoselektiv in eine andere, synthetisch nützliche funktionelle Gruppe umwandeln lässt. Es wurde nun gezeigt, dass ein hypervalentes Iodreagens mittels elektrophiler Demethylierung genau das erreicht. Im Zusammenspiel mit der Tamao‐Fleming‐Oxidation wird die Me3Si‐Gruppe ein Platzhalter für eine Hydroxygruppe.
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