Simple Methodology for the Aerobic N‑Methylation of Substituted Anilines Catalyzed by Zirconium Oxychloride Octahydrate, ZrOCl₂·8H₂O

A highly chemoselective methodology is described for the N-methylation of functionalized anilines with dimethyl carbonate (MeOCO₂Me, DMC) in the presence of ZrOCl₂·8H₂O. Dimethyl carbonate, which usually promotes methylation at T > 120 °C and eventually under inert atmosphere, was activated in the presence of zirconium oxychloride for the desired transformation at 90 °C under aerobic conditions. Aminophenols showed good reactivity in this transformation and produced the corresponding N-methylanilines, as the major products, with high selectivity. Catalyst reusability study confirmed that ZrOCl₂·8H₂O is a recyclable catalyst and its catalytic activity was remained unchanged at least after eight runs. Effect of some reaction parameters such as catalyst concentration, aniline/DMC mole ratio, reaction time, and temperature were also investigated.