Aminophosphine ligands

We developed a rapid synthesis of amino(di)phosphines of types I or II, achieved in two steps by the addition of nucleophilic amines to vinylphosphine oxides, which can then be reduced by silane to the corresponding phosphine ligands.
This paved a way for the synthesis of libraries of optically active PN and PNP ligands, by using chiral amines/aminoalcohols or chiral vinylphosphine oxides (containing stereogenic a phosphorus donor), which were examined as ligands in Pd-catalysed C-C and C-N coupling reactions, as well as ruthenium-catalysed (asymmetric) transfer hydrogenation of ketones. In the latter case, as the chirality of the N and P donors can be independently controlled, match/mismatch of chirality in these asymmetric processes can be examined. In these cases, ee’s in excess of 90% can be achieved. 

Proline-derived aminophosphines

The other part of the project focussed on the synthesis of proline-derived aminophosphines of type III and IV. Here we examined effects of combining different donor groups (PNN, PNP) within the chiral ligand scaffold, and the introduction of additional stereogenic centres (on carbon or phosphorus). These ligands were tested in Pd-catalysed asymmetric allylic substitution reactions, as well as Ru-catalysed asymmetric reduction of ketones. In all cases, ee’s in excess of 90% can be achieved. More interestingly are the observation of cooperative effects between donor groups.