Synthesis of silica-supported chiral ferrocenylphosphine ligands and theirapplication in some stereoselective reactions

Synthesis of new BPPFA analogues, having exchanged one of the N-methyl grou ps for a long (-C10H20-) or short (-C4H8-) alkyl chain with a terminal meth oxycarbonyl group, and their immobilization on silica are described. Immobi lization resulted in considerable lowering of the reaction rates as well as stereoselectivity in hydrogenation reactions. On the other hand, both homo geneous 3a as well as immobilized ligand 6a with a longer spacer (-C10H20-) have activities and enantioselectivities in allylic nucleophilic substitut ion comparable to the known BPPFA ligand. This is true also for homogeneous ligand 3b with a shorter chain (-C4H8-), but its immobilization resulted i n a big drop of activity as well as selectivity.