Screening of a phosphite-phosphoramidite ligand library for palladium-catalysed asymmetric allylic substitution reactions: the origin of enantioselectivity.
We have designed a new library of readily available, highly modular phosphite-phosphoramidite ligands for asymmetric allylic substitution reactions. They are easily prepared in one step from commercially available chiral 1,2-amino alcohols. The introduction of a phosphoramidite moiety into the ligand design is highly advantageous for the product outcome. This ligand library affords high reaction rates (TOFs of up to 800 mol (mol h)(-1)) and enantioselectivities (ees of up to 99%) and, at the same time, contains a broad range of disubstituted hindered and unhindered substrate types. NMR study of the Pd-pi-allyl intermediates provide a deeper understanding of the effect of the ligand parameters on the origin of enantioselectivity.
Pàmies
Oscar
O
Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, C/Marcel.lí Domingo s/n, 43007 Tarragona, Spain. oscar.pamies@urv.cat
Diéguez
Montserrat
M