Phosgene-Free Synthesis of Carbamates Using CO2and Titanium Alkoxides

A facile one-pot, phosgene-free method for the synthesis of N-phenylcarbamates is developed. Using this method, various aromatic carbamates could be prepared from aromatic amines, CO2and metal alkoxides. Aniline reacted with titanium methoxide (Ti(OMe)4) in the presence of CO2(5 MPa) to give methyl N-phenylcarbamate in 85% yield, in 20 min. Titanium residue could be regenerated by reaction with dimethyl carbonate at 220 °C for 16 h.The direct synthesis of carbamates from amines, CO2, and Ti(OMe)4was investigated. Under suitable reaction conditions, 2,4-DAT and 4,4'-MDA were transformed into the corresponding bis-carbamates, which play an important role in the polyurethane industry. Moreover, Ti(OMe)4could be recycled and reused, extending its application to industrial processes.