N-substituted carbamates syntheses with alkyl carbamates as carbonyl source over Ni-promoted Fe3O4 catalyst

A series of catalysts of magnetic iron oxide containing Ni with different nickel content were prepared with co-precipitation method and tested in the syntheses of N-substituted carbamates from various amines and alkyl carbamates. Under the optimized reaction conditions, various N-substituted carbamates were successfully synthesized with 90–98% isolated yield. The catalyst could be recovered based on the magnetic property of the catalyst and reused for five runs without deactivation. The catalysts were characterized with X-ray photoelectron spectroscopy, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption, and Mössbauer spectroscopy analyses. The results showed that the catalytic activity may be derived from the delicate synergy between Ni and Fe species resulted in specific basic sites. Quasi in situ FT-IR and isotopic tracer revealed that the formation of substituted urea was the key step and the N-substituted carbamate was formed via further alcoholysis of the substituted urea.

Graphical abstractA magnetic Ni/Fe3O4 catalyst was developed for the syntheses of N-substituted carbamates with amines and alkyl carbamates. Reaction pathway investigation revealed that the N-substituted carbamate was formed via urea intermediate.Figure optionsDownload full-size imageDownload high-quality image (81 K)Download as PowerPoint slideResearch highlights► Ni/Fe3O4 catalyst was developed for the N-substituted carbamates synthesis. ► N-substituted carbamate was formed via urea intermediate. ► Catalytic activity was derived from the delicate synergy between Ni and Fe species.