Studies On The Catalytic Asymmetric Cyanosilylation Of Ketones By Chiral Amino Acid Salts

Homochiral cyanohydrins are of synthetic interest as they may be elaborated into a number of key multifunctional intermediates. The asymmetric addition of TMSCN to ketones is one of the most direct, efficient and prevailing methods to obtain chiral cyanohydrins. Of particular interest to us was to explore this approach via the development of a catalytic asymmetric cyanation of ketones with readily accessible amino acid salts,In this dissertation, we described the first example of chiral organic salts as catalysts for asymmetric cyanosilylation of ketones. A broad range of aromatic,α,β-unsaturated, heterocyclic, aliphatic andα,α-dialkoxy-substituted ketones catalyzed by L-phenylglycine sodium salt gave the corresponding trimethylsilyl ethers of cyanohydrins in 75-96% yields with 86-97% enantioselectivities under mild reaction conditions.From the optimizing experiments in term of enantioselectivity, in this case, we know the following as the facts. Both the primary amine moiety and the metal carboxylate moiety of the catalyst were essential for the catalytic activity and asymmetric induction. And there is a strongл-лeffect between the catalyst and the ketones. Moreover, some key features associated with the use of L-phenylglycine sodium salt should be noteworthy. When the catalyst was stirred with TMSCN in THF for 0.5 h at 30 oC before ketone was added, the enantioselectivity was greatly improved from 54% to 80% ee at -20 oC and up to 94% ee at -45 oC. Interestingly, a small amount of water contained in the catalyst was crucial to retain...