Functionalized micelle-templated silicas (MTS) and their use as catalysts for fine chemicals

Abstract

Functionalization of micelle-templated silica (MTS) was achieved by silanation of the MTS surface by 3-amino and 3-halogeno-propyl alkoxysilane in an apolar solvent. The grafted halogeno organic moieties were further modified by halogen substitution of other functions such as piperidine, tetraalkyl guanidine, (-)-ephedrine, 3-[N,N′-bis-3-salicyldenamino propylamine] (Salpr) and 3-[N,N′-bis-3-(3,5-di-tert-butylsalicyldenamino) propylamine] (tSalpr). During the modification procedure, the regular mesoporous structure of the MTS support was preserved. MTS-bound primary and tertiary amine functions were effective immobilized catalysts for Knoevenagel condensation and selective monoglyceride synthesis. MTS-bound 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was an efficient base catalyst for performing transesterification reaction. Chiral β-aminoalcohols such as (-)-ephedrine grafted on MTS allowed the catalysed alkylation of benzaldehyde by diethylzinc with high conversion and selectivity in 1-phenyl-propanol and moderate enantioselectivity in the (1R) enantiomorph. Manganese (III) Salpr and tSalpr complexes linked to the MTS surface catalysed styrene epoxidation using iodosylbenzene. The efficiency of this latter catalysis should be improved by the use of other liganding molecules more resistant than salen-type ligands towards oxidation media.