Ligand-free PdII/AgI-catalysed electrophilic amidation of simple arenes with O-acetyl acetohydroxamic acid

Electrophilic amination (EA) involving transition metal-catalysed C-H activation of the arene has recently emerged as a promising method to directly construct aryl C(sp2)-N bonds. In EA, a leaving group (LG) is installed on nitrogen to overcome thermodynamic and kinetic barriers, as well as a polarity mismatch. However, many literature reports are limited to arenes carrying large directing groups and/or nitrogen coupling partners with extensive LGs. Many reactions also require additives (ligands, bases), often in superstoichiometric amounts. In addition, mechanistic information is often scarce. Herein we disclose a PdII-catalysed, AgI-mediated electrophilic amidation of simple arenes with O-acetyl acetohydroxamic acid (AcNHOAc). In contrast with previously reported systems, the reaction neither requires a ligand, nor superstoichiometric amounts of additives. Yields up to 50% were achieved, with up to 76% meta-selectivity. The catalytic system was optimized and the main yield-limiting factors were determined. Furthermore, we propose a mechanism only involving PdII species, in which coordination of AcNHOAc occurs before C-H activation. The mechanism is supported by experimental data from H/D exchange measurements, in situ XAS, FTIR, UV-Vis and NMR spectroscopy.