An indium triiodide-catalyzed substitution of the acetoxy group in alkyl acetates with thiosilanes provides access to a variety of thioethers. The method is efficient for a wide scope of acetates such as primary alkyl, secondary alkyl, tertiary alkyl, allylic, benzylic, and propargylic acetates.
Abstract:The substitution of a siloxy group using thiosilanes smoothly occurred in the presence of InI 3 catalyst to yield the corresponding thioethers. InI 3 was a specifically effective catalyst in this reaction system, while other typical Lewis acids such as BF 3 ·OEt 2 , AlCl 3 , and TiCl 4 were ineffective. Various silyl ethers such as primary alkyl, secondary alkyl, tertiary alkyl, allylic, benzylic, and propargylic types were applicable. In addition, bulky OSitBuMe 2 and OSiiPr 3 groups, other than the OSiMe 3 group, were successfully substituted. The substitution reaction of enantiopure secondary benzylic silyl ether yielded the corresponding racemic thioether product, which suggested that the reaction of tertiary alkyl, secondary alkyl, benzylic, and propargylic silyl ethers would proceed via a S N 1 mechanism.
Acylierung mit Additiv: Bei der Titelreaktion, einer Kondensation von Carbonsäuren mit Ketensilylacetalen (siehe Schema), wird dem Additiv (MeO)3SiH eine wichtige Rolle zugeschrieben. Die Umsetzung ist kompatibel mit verschiedenartigen funktionellen Gruppen, darunter auch Alken‐, Alkin‐, Chlorid‐, Alkohol‐, Ester‐ und Nitrofunktionen.
The method is highly selective for the acetate moiety as is shown by formation of main product (XVII). Furthermore, a tertiary acetate is more reactive than a primary one [cf. (XIV)]. The process can be extended to ring-opening of lactones to yield ω-thio functionalized carboxylic acids (XXIII). -(NISHIMOTO, Y.; OKITA, A.; YASUDA, M.; BABA*, A.; Org. Lett. 14 (2012) 7, 1846-1849, http://dx.
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