2019 Volume 55 Issue 5 Pages 175-180
A facile one-pot, halogen-free method of synthesizing aromatic urethane directly from carbon dioxide（ CO2）,amines, and metal alkoxide is developed. Metal alkoxide could be regenerated upon reaction with alcohol duringwater removal. Notably, various aromatic urethane could be prepared from aromatic amine, CO2, and metalalkoxides. Aniline reacted with titanium methoxide （Ti（OMe）4） in the presence of CO2（ 5 MPa） to give thecorresponding methyl N-phenyl carbamate （MPC） in 85％ yield within 20 min. Ti（OMe）4 can be regeneratedby a reaction with DMC at 220℃. This methodology opens up a new route for the production of urethanes, especiallyaromatic urethanes, which are important precursors for polyurethane（ PUR）. A tentative mechanismfor this reaction is proposed, and the negative ρ value determined by Hammett analysis indicates nucleophilicattack of the amine onto the carbonyl species of Ti-carbonate complex derived from reaction of Ti（OMe）4 andCO2.
