抄録
We developed a new class of chiral phosphorus ligands: P-chirogenic diaminophosphine oxides. These chiral ligands were prepared from aspartic acid, and applied to Pd-catalyzed asymmetric allylic substitution. In addition to asymmetric allylic alkylation and amination of allyl acetate 6, Pd-catalyzed asymmetric allylic substitution with various β-keto esters was proceeded in the presence of Zn(OAc)2 to provide the corresponding products with a quaternary carbon in up to 94% ee. Allyl acetates conjugated with a ketone (11) or an ester group (12) were also applicable to this catalyst system, affording the products 15 and 16 with high enentioselectivity. Mechanistic studies indicated that two ligand molecules, which were generated in situ by BSA-induced tautomerization of diaminophosphine oxides, coordinated to Pd metal in a monodentate fashion, resulting in the formation of the catalytically active Pd complex (Pd:ligand = 1:2).