Chromatography-free synthesis of carbamates from CO2 catalyzed by a green and recyclable biobased ionic liquid/Cu2O system

Abstract

Carbamates and related derivatives are crucial skeletons for pesticide design and pharmaceutical chemistry. Recently, a synthetic route for the production of carbamates has drawn great attention, which assembles the economical, renewable and non-toxic CO2 with propargyl alcohols and amines. This route is 100% atom-economical and free of traditional carbon sources (CO, phosgene, etc.), thus attracting scientists to develop numerous catalytic methods for its effective applications. However, the carbamates produced in these methods generally contained residual catalysts, solvents or byproducts. Consequently, column chromatography purification is inevitably required for all the reports up to now. This limitation has fundamentally hindered the practical application of this route. Herein, a chromatography-free method was proposed for the first time. With the catalysis of a green and economical Cu2O/biobased ionic liquid system, the carbamates could be obtained in good to excellent yields and purity. Additionally, the catalytic metal loading reached the lowest level reported by far under 1 bar of CO2. Furthermore, this catalytic system could be recycled and reused for at least 5 times.