Abstract
TUD-1 has been used as Bronsted acidic mesoporous support for the immobilization of a chiral cyclopropanation catalyst. Bronsted acid sites were introduced by supporting phosphotungstic acid on all alumina TUD-1 matrix (PW-TUD-Al2O3) or by substitution of Si by Al in all silica TUD-1 matrix (Al-TUD-1). The chiral cyclopropanation catalyst Cu(I)- 2,2'-methylenebis [(4R,5S)-4,5-diphenyl-4,5-dihydro-1,3-oxazole] was immobilized by different noncovalent immobilization techniques; ion-exchange in solution and solid-gas ion-exchange. The chiral cyclopropa nation catalyst was adsorbed on PW-TUD-Al2O3 during ion-exchange in solution. This catalyst system displayed high leaching of copper reaching values of 21%. While using Al-TUD-1 as support copper was introduced as CuCl at temperatures from 550 to 850 degrees C subsequently followed by introduction of the ligand. Noncovalent immobilization by solid-gas ion-exchange of CuCl on Al-TUD-1 resulted in heterogenous catalyst with only 1% leaching of copper but also moderate results in the cyclopropa nation of styrene in terms of yield (33%) and enantioselectivities. (C) 2009 Elsevier B.V. All rights reserved.