Synthesis of Methyl N-Phenyl Carbamate Catalyzed by Ionic Liquid-Promoted Zinc Acetate

A series of ionic liquid-promoted zinc acetate catalysts (Zn(OAc)2-ILs) were prepared by separately mixing anhydrous zinc acetate with one of some ionic liquids, and their catalytic performance for the synthesis of methyl N-phenyl carbamate (MPC) from aniline and dimethyl carbonate (DMC) was evaluated. Among the catalysts, Zn(OAc)2-[bmim]PF6 showed the best catalytic performance. Under the suitable reaction conditions, aniline conversion and MPC selectivity were 99.8% and 99.1%, respectively. Moreover, Zn(OAc)2-[bmim]PF6 could be used five times without a significant loss in its catalytic performance. The mechanism for the promotion of ionic liquid [bmim]PF6 on the catalytic performance of zinc acetate was investigated by means of FT-IR analysis. The results show that a hydrogen bond is formed between the carbonyl oxygen of zinc acetate and the C2–H on an imidazoiume ring of [bmim]PF6. As a result, the zinc acetate changes from a bidentate to a unidentate coordination structure. Simultaneously, this chang...