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

A new heterogeneous system for catalytic trimethylsilylcyanation of benzaldehyde has been developed by immobilizing Ti(IV) salen onto ordered mesoporous silica (MCM-41). The immobilization was performed according to different methods: (i) direct condensation of silanol on the silica surface with Ti(IV) salen and (ii) multigrafting of salicylaldehyde derivatives and diaminocyclohexane using 3-mercaptopropyl-functionalized MCM-41 as a starting material. The heterogenized salen catalysts showed a high enantioselectivity for the addition of trimethylsilyl cyanide to benzaldehyde.