Dual role of carboxylic acid additive: Mechanistic studies and implication for the asymmetric C-H amidation Dedicated to Professor Yoshiaki Nakao on his receipt of the Tetrahedron Young Investigator Award

Abstract

Acid additive effects in the Ir-catalyzed CeH amidation of arylphosphoryl compounds were examined. Structure of catalytically active metal species was elucidated: mono-cationic iridium catalyst [Cp*Ir(- III)(OAc)](NTf2) being mainly responsible for the CeH bond activation. Mechanistic studies revealed a dual role of carboxylic acid additive operating both in the generation of an iridacyclic intermediate and in the protodemetalation process to release amidated products. The fact that asymmetric CeH amidation was achieved albeit in moderate enantioselectivity by using chiral carboxylic acid supports our proposal especially with regard to the role of acid additive. © 2015 Elsevier Ltd. All rights reserved