Heterogenised chiral amines as environmentally friendly base catalysts for enantioselective Michael addition

Heterogenised chiral amines on silica, MCM-41 and delaminated zeolite ITQ-2 have been prepared and fully characterised. These new catalysts have been tested in the Michael addition of ethyl 2-oxocycloalkanecarboxylates to acrolein. The heterogenised amines presented higher rates than referable homogeneous counterparts; moreover these catalysts were recovered quantitatively by simple filtration and reused in without loss of activity. MCM-heterogenised catalysts show slightly lower reaction rate but improved enantiomeric excess than silica-heterogenised materials, especially with bulky reagents. The use of a high specific surface support (ITQ-2) does not imply an improvement in the catalytic activity of the material.