Studies On Cyanosilylation Of Ketones Catalyzed By Organocatalysts

Cyanohydrins are versatile intermediates in the context of organic synthesis, especially, in asymmetric synthesis. The addition of TMSCN to Ketone is the most direct, efficient, and prevailing strategy. In this dissertation, a novel efficient easily conducted catalytic system has been developed, so as to avoid the high price, toxicity, pollution, waste treatment and product contamination caused by the metal catalysts. And we attempt to apply this catalytic system to the asymmetric silylcyanation. Achiral quaternary ammonium salt and N-oxide (down to 2.5 mol %) were used to afford racemic cyanohydrins with excellent isolated yields (up to 99%). This approach covers the substrate range of aliphatic, aromatic, heterocyclic and steric hindrance ketones. The low catalyst loading, short reaction time, mild conditions and the good generality of substrates all make this protocol practical. According to the control experiments and the experiment phenomena, a possible catalytic cycle and a possible key intermediate are rationally proposed to illustrate the experimental observations. 23 chiral quaternary ammonium salts were prepared and evaluated for the enantioselective addition of TMSCN to ketones.