Catalytic Ester−Amide Exchange Using Group (IV) Metal Alkoxide−Activator Complexes

A process for preparation of amides from unactivated esters and amines has been developed
using a catalytic system comprised of group (IV) metal alkoxides in conjunction with additives including
1-hydroxy-7-azabenzotriazole (HOAt). In general, ester−amide exchange proceeds using a variety of
structurally diverse esters and amines without azeotropic reflux to remove the alcohol byproduct. Initial
mechanistic studies on the Zr(Ot-Bu)4−HOAt system revealed that the active catalyst is a novel, dimeric
zirconium complex as determined by X-ray crystallography.