Halogen-free synthesis of carbamates from CO₂ and amines using titanium alkoxides

Abstract

A direct sythesis of carbamates from amines and carbon dioxide in the presence of Ti(OR)₄ (R = Me, Et, nPr, nBu) was investigated. Aniline was reacted with Ti(OnBu)₄ in the presence of carbon dioxide to give the corresponding n-butyl N-phenylcarbamate (BPC) in nearly quantitative yield (99%) within 20 min. Furthermore, Ti(OnBu)₄ could be regenerated upon reaction with n-butanol during water removal. The recovered Ti(OnBu)₄ could then be reused in a subsequent reaction.