Exploring the Electronic and Steric Effects of Hemilabile (P^N) Ligands in Redox Gold Catalysis: Application to the Cross-Coupling of Aliphatic Amines with Aryl Iodides

In this work, we present the synthesis of 17 new DalPhos-based (P^N) ligands for redox gold catalysis, featuring various substituents at the C4, C5, C6 of aryl ring and the hemilabile nitrogen handle. The electronic and steric effects of these new hemilabile (P^N) ligands on the oxidative addition of the Au(I) complexes with C(sp2)-Br bonds have been studied through UV-Vis spectroscopy. The experiments revealed that the electron rich substituents on the -C4 and -C5 positions of the aryl ring slightly enhanced the rate of oxidative addition of Au(I)NTf2 complexes with C(sp2)-Br bonds. In contrast, gold complexes with electron-poor substituents on the -C4 and -C5 positions and sterically hindered -C6 substituted lig-ands exhibited slower rate of oxidative addition as compared to MeDalPhosAuNTf2. The Au(I)NTf2 complexes of N-aryl substituted ligands L12-L17 were found to undergo sluggish oxidative addition with aryl iodides; however, ligands L12-L14 exhibited high efficiency (up to 94% yield) in the previously reported C-N cross-coupling of aryl iodides with aro-matic amines. Further, we report an unprecedented gold-catalyzed arylation of aliphatic amines by using the ligand (L6) with -OMe group at the -C5 position. The electronically rich ligand L6 was found to outperform the commonly used MeDalPhos ligand by effectively circumventing the challenge of catalyst deactivation, often encountered in the transition metal-catalyzed amination reactions.