Asymmetric Trimethylsilylcyanation of Benzaldehyde Catalyzed by Chiral Ti(IV) Salen Complexes Immobilized on MCM-41

摘要

The efficiency of new unsymmetrical chiral salen ligands was examined in the asymmetricrntrimethylsilylcyanation of benzaldehyde. A very high level of enantioselectivity wasrnattainable over chiral Ti(IV) salen complexes prepared from salicylaldehyde and 3,5-Di-tert-rnbutylsalicylaldehyde derivative as compared to the conventional salen catalyst. Enantiomericrnexcess of the corresponding reaction product was generally more than 70% over unsymmetricrnchiral salen catalysts. The chiral Titanium(IV) salen complexes immobilized on a mesoporousrnMCM-41 by multi grafting method showed a relatively high enantioselectivity for thernaddition of trimethylsilyl cyanide to the benzaldehyde.