Picolinaldehyde‐Zinc(II)‐Palladium(0) Catalytic System for the Asymmetric α‐Allylation of N‐Unprotected Amino Esters

Abstract

AbstractReported in this work is a synergistic ternary achiral picolinaldehyde‐Zn(II)‐chiral palladium complex system for the highly enantioselective α‐allylation of N‐unprotected amino esters. By utilizing a variety of allylic carbonates or vinyl benzoxazinanones as substrates, α‐allyl α‐amino esters were obtained in high yields (up to 96 %) with high enantioselectivities (up to 98 % ee). Control experiments suggest that the coordination of Zn(II) with the Schiff base intermediate enhances the acidity of the α‐C−H bonds of amino esters, thereby favoring α‐allylation over intrinsic N‐allylation. Furthermore, NMR studies reveal an interaction between the chiral palladium complex and the Zn(II)‐Schiff base intermediate, leading to the formation of a picolinaldehyde‐Zn(II)‐Pd(0) catalytic system.